A method for acquiring signals using overlapping receiving coils for MR imaging.

Abstract

According to the present invention, a method is provided for selecting a set of coil elements of a high-frequency coil system 2 having a plurality of coil elements 4 to receive a magnetic resonance signal in a region of interest, the method comprising: determining a signal-to-noise ranking of the plurality of coil elements 4 with respect to a region of interest; assigning the coil elements 4 to a first type A and a second type B based on the determined signal-to-noise ranking, wherein coil elements having a signal-to-noise ratio higher than a predetermined threshold are assigned to type A, and coil elements having a signal-to-noise ratio lower than a predetermined threshold are assigned to type B; determining the coupling effect of each coil element 4 of the high-frequency coil system 2 with respect to a region of interest; grouping the coil elements 4 assigned to the first type A or the second type B into a primary coil group 8 and a secondary coil group 9 based on the determined coupling effect and signal-to-noise ratio, wherein the same type A or B coil elements 4 having mutual coupling effects are assigned to at least partially different coil groups 8 and 9; and selecting a coil element from either the primary coil group 8 or the secondary coil group 9 to receive a magnetic resonance signal in a region of interest. In this way, the quality of MR imaging can be improved by selecting and combining the coil elements 4 so that the maximum possible number of coil elements 4 are used to receive electromagnetic induction signals while increasing the SNR, without simply excluding coil elements 4 that do not provide sufficient information.

Description

Technical Field

[0001] The present invention relates to the field of magnetic resonance (MR) imaging, and more particularly to a method for collecting electromagnetic induction signals using one or more overlapping (overlapping) receive coils.

Background Art

[0002] In magnetic resonance imaging, various receive coils are used to receive electromagnetic induction signals. These electromagnetic induction signals are converted into digital signals using an analog-to-digital conversion module, and then various images used for diagnosis are reconstructed.

[0003] Magnetic resonance imaging can be widely clinically applied when used for collection of various parts of the body. Subsequently, there are various receive coils for reception. With the development of magnetic resonance applications, clinical examples of simultaneously using two or more receive coils or using the same flexible receive coil for different anatomical structures are increasing. In such clinical scenarios where such receive coils are used, overlap always occurs between channels within a coil or between multiple coils, resulting in coupling and a decrease in SNR (signal-to-noise ratio). Therefore, the image quality deteriorates. Magnetic resonance collection is usually performed by multiple average accumulations to improve the signal-to-noise ratio (SNR), especially when the main magnetic field is relatively low, for example, 1.5T or less, or when the imaging field of view is relatively small.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In conventional scanning, the use of the same coil elements with overlapping coil elements in different acquisition stages of multiple average acquisitions leads to a decrease in signal-to-noise ratio (SNR). "Coupling effect between overlapping coil elements" means that two coil elements are positioned relative to each other, resulting in a coupling effect that degrades image quality. This occurs when these two coil elements geometrically overlap or are positioned very close to each other. Overlap can exist between two coil elements of two different rigid receiving coils or the same flexible receiving coil.

[0005] This conventional acquisition strategy leads to inaccurate results because channels with low SNR are simply excluded, or channels with overlapping channels are simply not used, or are used with exactly the same weighting. These strategies also apply to channels with flexible coil coupling. In the acquisition phase, only combination modes of the same coil element are used. These conventional acquisition strategies do not fully utilize the available receiving channels and do not fully address the coupling effects between some of the channels that are used.

[0006] U.S. Patent Application Publication 2011 / 006766A1 describes a method for selecting a set of coil elements from a number of physical coil elements included in a coil array for performing magnetic resonance imaging scans. The coil elements are ranked according to a noise sensitivity matrix and a calculated amount of information. The most appropriate set of coil elements is selected according to this ranking.

[0007] The objective of this invention is not to simply exclude coil elements that do not supply sufficient information, but rather to improve the quality of MR images by selecting and combining coil elements, thereby using as many coil elements as possible for receiving electromagnetic induction signals while improving the signal-to-noise ratio (SNR). [Means for solving the problem]

[0008] According to the present invention, this objective is addressed by the subject matter of the independent claim. Preferred embodiments of the present invention are described in the dependent claims.

[0009] Accordingly, the present invention provides a method for selecting a set of coil elements in a high-frequency coil system having a plurality of coil elements to receive a magnetic resonance signal in a region of interest, the method comprising: determining a signal-to-noise ranking of the plurality of coil elements (4) for a region of interest; assigning the coil elements (4) to a first type A and a second type B based on the determined signal-to-noise ranking, wherein coil elements having a signal-to-noise ratio higher than a predetermined threshold are assigned to type A, and coil elements having a signal-to-noise ratio lower than a predetermined threshold are assigned to type B; determining the coupling effect of each coil element (4) of the high-frequency coil system (2) for a region of interest; grouping the coil elements (4) assigned to the first type A or the second type B into a primary coil group (8) and a secondary coil group (9) based on the determined coupling effect and signal-to-noise ratio, wherein coil elements (4) having mutual coupling effects with each other are assigned to at least partially different coil groups (8, 9); and selecting a coil element from either the primary coil group (8) or the secondary coil group (9) to receive a magnetic resonance signal in a region of interest.

[0010] As explained above, it is important to group and combine coil elements to reliably receive electromagnetic induction signals with the maximum number of coil elements and the highest SNR. In particular, the coil elements correspond to coil channels.

[0011] When receiving data simultaneously using two or more receiving coils, all coil elements that can be used for reception are classified into two types. Coil elements with a higher SNR are assigned to Type A, and coil elements with a lower SNR are assigned to Type B. According to Type A and B, the coil elements are divided into two groups: a primary coil group and a secondary coil group.

[0012] The essential point is that coil elements, which have a coupling effect with each other, are assigned to at least partially separate coil groups and are therefore divided.

[0013] The signal-to-noise ranking means arranging all coil elements according to their contribution to the SNR, that is, from those with a high contribution to the SNR to those with a low contribution. These coil elements are assigned to either Type A, which has a higher contribution to the SNR, or Type B, which has a lower contribution to the SNR, according to a predetermined threshold.

[0014] Generally, mutual coupling occurs between two overlapping elements, so the method of separation ensures that, in each group, the coupling effect between two overlapping coil elements within the same group is significantly reduced or even completely eliminated.

[0015] In particular, a noise correlation matrix and / or coil sensitivity map are used to determine whether two coil elements have a coupling effect with each other.

[0016] According to a preferred embodiment of the present invention, the method further comprises the steps of: assigning a type A coil element without coupling effect, a type B coil element without coupling effect, and a type A coil element that couples with a type B coil element to a primary coil group; assigning a type A coil element without coupling effect, a type B coil element without coupling effect, and a type B coil element that couples with a type A coil element to a secondary coil group; and assigning two identical type A or B coil elements having a mutual coupling effect to different coil groups according to their signal-to-noise ratio, wherein the coil element having a higher signal-to-noise ratio is assigned to the primary coil group and the coil element having a lower signal-to-noise ratio is assigned to the secondary coil group.

[0017] The primary coil group has Type A coil elements, more specifically channels for coils that contribute relatively large to the SNR, and the secondary coil group has Type B coil elements, more specifically channels for coils that contribute relatively small to the SNR. At the same time, coil elements that have a coupling effect with other elements are also marked. Coil elements that have a mutual coupling effect within the same group are separated. This determines the first and second coil elements of the coil elements that have a mutual coupling effect within the same group. The first coil element has a higher SNR than the second coil element. The first coil element is assigned to the primary coil group, and the second coil element is assigned to the secondary coil group. "Assigned" preferably means that the coil element is moved from its original group to the other group. For example, if two coil elements in the primary coil group have a mutual coupling effect, the coil element with the higher SNR remains in the primary coil group, and the second coil element is moved to the secondary coil group. In this way, coil elements with mutual coupling effects are separated into different groups and used for different scans. The channels of coils without coupling effects are divided into two coil groups, namely, a primary coil group and a secondary coil group.

[0018] This results in the construction of two coil groups: a primary coil group and a secondary coil group. The primary coil group includes coil elements with an SNR higher than a predetermined threshold (Type A coil elements) and Type A and Type B coil elements without coupling effects. The secondary coil group includes coil elements with an SNR lower than a predetermined threshold (Type B coil elements) and Type A and Type B coil elements without coupling effects. Since the coil elements of different groups are used separately for different scans, coil elements in the primary coil group that have a coupling effect with the coil elements of the secondary coil group are not a problem. Coil elements that have a mutual coupling effect within the same coil group, for example, two coil elements with a mutual coupling effect that are both grouped in the primary coil group, are divided into different coil groups by placing or rearranging the coil elements with the higher signal-to-noise ratio in the primary coil group and the coil elements with the lower signal-to-noise ratio in the secondary coil group, as described above.

[0019] Preferably, the method further comprises the step of pre-scanning the region of interest to determine the signal-to-noise ranking and coupling effect.

[0020] Using the pre-scan data generated during the pre-scan, the coil elements are analyzed once per receiving coil device before the actual MRI scan begins. Based on the pre-scan data, the coil channels are grouped and divided into two groups: a primary coil group and a secondary coil group. Preferably, in the subsequent MRI scan, some of the acquisitions use the coil elements of the primary coil group, and another portion of the acquisitions use the coil elements of the secondary coil group, which minimizes the effects of coupling between channels.

[0021] According to a preferred embodiment of the present invention, the high-frequency coil system has at least one flexible receiving coil or at least two rigid receiving coils, each receiving coil having several coil elements, and at least two of the coil elements are arranged such that they at least partially overlap each other during a magnetic resonance imaging scan.

[0022] A coil system has multiple coils used in combination or a single flexible coil. "Partially overlapping" means that two coil elements are positioned relative to each other, resulting in a coupling effect between the two overlapping coil elements that leads to image quality degradation. This occurs when these two coil elements geometrically overlap or are positioned very close to each other. Overlap can exist between two coil elements of two different rigid receiving coils or the same flexible receiving coil.

[0023] According to a preferred embodiment of the present invention, the method further comprises the steps of: excluding coil elements having a signal-to-noise ratio lower than a second predetermined threshold based on a determined signal-to-noise ranking; and grouping the remaining coil elements as described above.

[0024] Specifically, exclusion means ignoring the coil element in order to receive the magnetic resonance signal. Coil elements whose SNR is lower than the second threshold, which is the SNR limiting threshold, are completely excluded. Then, all coil elements that can be used for reception are divided into two groups, a primary coil group and a secondary coil group, based on their contribution to the SNR and coupling effect. Specifically, the second threshold is lower than the first predetermined threshold for dividing the coil elements into two groups.

[0025] According to a preferred embodiment of the present invention, three or more coil elements of the same type A or B having a mutual coupling effect are partially assigned to different groups according to the signal-to-noise ratio. Thereby, the coil element having the highest signal-to-noise ratio is assigned to the primary coil group, the coil element having the second highest signal-to-noise ratio is assigned to the secondary coil group, and the coil elements having a lower signal-to-noise ratio are excluded. In some cases, for example, when using a very large flexible coil for a small anatomical structure, folding or blending the receiving coil into several layers, or using two or more receiving coils simultaneously, there may be three or more coupling loops within the same coil group. Then, the coil element with the highest SNR in the primary coil group remains in the primary coil group, and the coil element with the second highest SNR is moved to the secondary coil group. At the same time, the coil element with the highest SNR in the secondary coil group is moved to the primary coil group, and the coil element with the second highest SNR in the secondary coil group remains in the secondary coil group. The remaining coil elements having a mutual coupling effect within the same group are removed and not used for the scan. As a result, the mutual coupling effect induced by the overlapping coil elements within the same group is completely eliminated, and the scan quality is further improved.

[0026] According to a preferred embodiment of the present invention, the method further includes selecting the coil elements of the primary coil group to receive electromagnetic induction signals during a magnetic resonance imaging scan when the number of signal acquisitions is 1, and when the number of signal acquisitions is greater than 1, selecting the coil elements of the primary coil group for the first acquisition and selecting the coil elements of the secondary coil group for a second acquisition different from the first acquisition to receive electromagnetic induction signals during a magnetic resonance imaging scan.

[0027] This new acquisition strategy assigns the acquisition of multiple average accumulations to a primary coil group and a secondary coil group. When the number of signal acquisitions (NSA) is only once, the coil elements of the primary coil group are used to receive electromagnetic induction signals during a magnetic resonance imaging scan. When the number of acquisitions exceeds 1, to receive electromagnetic induction signals during a magnetic resonance imaging scan, the coil elements of the primary coil group are used for the first acquisition, and it is ensured that the coil elements of the secondary coil group are used for the second acquisition. In this way, since the coil elements of different coil groups are used separately to receive signals, the mutual coupling effect can be avoided.

[0028] According to a preferred embodiment of the present invention, the method further includes, when the number of signal acquisitions is greater than 1 and odd, selecting the coil elements of the primary coil group and the secondary coil group to receive electromagnetic induction signals, in which case the signal is received one more time from the coil elements of the primary coil group than from the coil elements of the secondary coil group; and when the number of signal acquisitions is greater than 1 and not odd (even), selecting the coil elements of the primary coil group and the secondary coil group for each half of the number of signal acquisitions to receive electromagnetic induction signals.

[0029] Thus, when the number of signal acquisitions is 2 or more, the number of acquisitions using the primary coil group is equal to the number of acquisitions using the secondary coil group, or the number of times the primary coil group is used is one more. Compared with the conventional cumulative average acquisition, there is no increase in the total scan time in the proposed strategy. However, the mutual coupling effect caused by the physical overlap between channels due to using multiple coils simultaneously or using one flexible coil with some channels overlapping can be eliminated. Thereby, the signal-to-noise ratio is improved.

[0030] The number of signal acquisitions (NSA) can be divided into two parts: the part using the primary coil group to receive the signal (NP) and the part using the secondary coil group to receive the signal (NS). NSA = NP + NS

[0031] The coil elements of the primary coil group are used in one of the NP portions according to the following equation: TIFF2026510734000002.tif933

[0032] The coil elements of the secondary coil group are used in the other part NS according to the following equation: TIFF2026510734000003.tif925

[0033] Furthermore, according to the present invention, a magnetic resonance imaging system is provided, A high-frequency coil system having multiple coil elements for receiving magnetic resonance signals in a region of interest, An evaluation unit adapted to determine the signal-to-noise ranking of the plurality of coil elements with respect to the region of interest, and to determine the coupling effect of each coil element of the high-frequency coil system with respect to the region of interest, The evaluation unit is further adapted to group the coil elements into Type A and Type B based on the determined signal-to-noise ranking, with coil elements having a signal-to-noise ratio higher than a predetermined threshold being grouped as Type A, and coil elements having a signal-to-noise ratio lower than a predetermined threshold being grouped as Type B. The evaluation unit is further adapted to group coil elements assigned to a first type A or a second type B into a first coil group and a second coil group based on the determined coupling effect and signal-to-noise ratio, and the evaluation unit is adapted to group coil elements that have a coupling effect with each other into different coil groups. A control unit adapted to select either a primary coil group or a secondary coil group of coil elements to receive a magnetic resonance signal in the region of interest, A magnetic resonance imaging system having the following characteristics is provided.

[0034] The high-frequency coil system comprises an evaluation unit and a control unit adapted to group coil elements according to SNR ranking and select coil elements from each group to receive magnetic resonance signals as described above.

[0035] According to a preferred embodiment of the present invention, the evaluation unit assigns a primary coil group to a type A coil element without coupling effect, a type B coil element without coupling effect, and a type A coil element coupled with a type B coil element; assigns a secondary coil group to a type A coil element without coupling effect, a type B coil element without coupling effect, and a type B coil element coupled with a type A coil element; and assigns two coil elements of the same type A or B having mutual coupling effect to different coil groups according to the signal-to-noise ratio, in which case the coil element having a higher signal-to-noise ratio is assigned to the primary coil group and the coil element having a lower signal-to-noise ratio is assigned to the secondary coil group.

[0036] Preferably, the control unit is further adapted to pre-scan the region of interest to determine the signal-to-noise ranking and coupling effects.

[0037] According to a preferred embodiment of the present invention, the high-frequency coil system has at least one flexible receiving coil or at least two rigid receiving coils, each receiving coil having several coil elements, and at least two of the coil elements are arranged such that they at least partially overlap each other during a magnetic resonance imaging scan.

[0038] According to a preferred embodiment of the present invention, the evaluation unit is further adapted to remove coil elements having a signal-to-noise ratio lower than a second predetermined threshold based on the determined signal-to-noise ranking, as described above, and to group the remaining coils together.

[0039] Therefore, the evaluation unit can pre-scan the coil elements, rank them according to their SNR, remove coil elements with a signal-to-noise ratio lower than a second predetermined threshold, and group them into primary coil groups and secondary coil groups. The control unit can then select the coil elements from each group to receive the magnetic resonance signal.

[0040] According to a preferred embodiment of the present invention, the evaluation unit is further adapted to group the coil elements into primary coil groups and secondary coil groups based on the determined signal-to-noise ranking and coupling effect, wherein three or more coil elements having mutual coupling effects within the same group are partially assigned to different groups according to the signal-to-noise ratio, the coil element with the highest signal-to-noise ratio is assigned to the primary coil group, the coil element with the second highest signal-to-noise ratio is assigned to the secondary coil group, and the coil element or coil element with a lower signal-to-noise ratio is removed.

[0041] According to a preferred embodiment of the present invention, the control unit is adapted to select a coil element from the primary coil group to receive an electromagnetic induction signal during a magnetic resonance imaging scan when the number of signal acquisitions is 1, and to select a coil element from the primary coil group for a first acquisition and a coil element from the secondary coil group for a second acquisition different from the first acquisition to receive an electromagnetic induction signal during a magnetic resonance imaging scan when the number of signal acquisitions is greater than 1.

[0042] According to a preferred embodiment of the present invention, the control unit is adapted to select coil elements from the primary coil group and the secondary coil group to receive electromagnetic induction signals when the number of signal acquisitions is greater than one and odd, in which case one more signal is received from the coil elements of the primary coil group than from the secondary coil group, and when the number of signal acquisitions is greater than one and even (not odd), to select coil elements from the primary coil group and the secondary coil group for each half of the number of signal acquisitions, respectively, to receive electromagnetic induction signals.

[0043] In magnetic resonance data acquisition, signal averaging is typically used to improve the signal-to-noise ratio (SNR). According to the preferred embodiment of the present invention described above, the acquisition strategy assigns multiple averaging cumulative acquisitions to primary and secondary coil groups, ensuring that the primary coil group is used when there is only one acquisition, and that when there are two or more acquisitions, the number of acquisitions using the primary coil group is equal to or one more than the number of acquisitions using the secondary coil group. Compared to conventional cumulative averaging acquisition, the proposed strategy does not increase the total scan time and eliminates the mutual coupling effect caused by physical overlap between channels due to the simultaneous use of multiple coils or a single flexible coil where parts of the channels overlap. Thus, the signal-to-noise ratio can be improved.

[0044] Furthermore, according to the present invention, when executed on a processor, a non-temporary computer-readable medium is provided for storing instructions for causing a high-frequency receiver system for an MRI apparatus to perform the above-described method.

[0045] These and other aspects of the present invention will become apparent from and be described with reference to the embodiments described below. However, such embodiments do not necessarily represent the entire scope of the present invention, and therefore, please refer to the claims and this specification to interpret the scope of the present invention. [Brief explanation of the drawing]

[0046] [Figure 1] A schematic diagram illustrating a magnetic resonance imaging system according to a preferred embodiment of the present invention. [Figure 2] A schematic diagram showing a process scheme for grouping coil elements according to a preferred embodiment of the present invention. [Figure 3] A schematic diagram illustrating a method for receiving electromagnetic induction signals using a high-frequency receiver system according to a preferred embodiment of the present invention. [Modes for carrying out the invention]

[0047] Figure 1 schematically shows a magnetic resonance imaging system 1 according to a preferred embodiment of the present invention. The magnetic resonance imaging system 1 includes an MRI device. A subject to be examined 5 is placed inside the MRI device. For an MRI scan, the subject to be examined is covered by a receiving coil 3 of a high-frequency receiver system 2. The receiving coil 3 is flexible and is wrapped around the subject to be examined 5 such that the coil elements 4 of the receiving coil 3 partially overlap. To avoid coupling effects and improve the SNR and quality of the MRI scan, an evaluation unit 7 and a control unit 6 are adapted to group the coil elements according to the specific positions of the receiving coil 3. The evaluation unit and the control unit can be incorporated into one identical unit, which may be embodied by a processor, a group of processors, a computer, or a computing system.

[0048] Figure 2 schematically shows a grouping scheme for coil elements 4, specifically, a single flexible coil 3 having overlapping portions used as shown in Figure 1. In the first step, there are several coil elements 4, either the same receiving coil or different receiving coils that partially overlap, and they are arranged to partially overlap. In the next step, the coil elements 4 are ranked according to their contribution to the SNR and then classified into Type A and Type B. Type A coil elements have a higher contribution to the SNR, and Type B coil elements have a lower contribution to the SNR. Furthermore, the coupling effect of the coil elements is determined. There are Type A coil elements 10 with no coupling effect, Type A coil elements 10a with the same type of coupling effect, and Type A coil elements 10b with other types of coupling effect. Similarly, there are Type B coil elements 11 with no coupling effect, Type B coil elements 11a with the same type of coupling effect, and Type B coil elements 11b with other types of coupling effect. Based on the determined coupling effect, in the next step, the coil elements are grouped into intermediate primary coil group 8' and intermediate secondary coil group 9'. If the contribution to the SNR is higher than a predetermined threshold (Type A), coil elements 10, 10a, and 10b are grouped into intermediate primary coil group 8'. If the contribution to the SNR is less than a predetermined threshold (Type B), coil elements 11, 11a, and 11b are grouped into intermediate secondary coil group 9'. Coil elements 10 and 11 that do not have a coupling effect are grouped into intermediate primary coil group 8' and intermediate secondary coil group 9'. Figure 2 shows that intermediate primary coil group 8' and intermediate secondary coil group 9' overlap and both include coil elements 10 and 11 that do not have a coupling effect.

[0049] In some cases, for example, when using a very large flexible coil for a small anatomical structure, or when folding or blending the receiving coil into several layers, or when using two or more receiving coils simultaneously, there may be two or more coupling loops within the same coil group. Then, in the next step, this "marked coupling" is used in conjunction with the SNR ranking to select the top two elements 10a.1 and 10a.2 for the elements with mutual coupling 10a in the intermediate primary coil group 8', leaving the coil element 10a.1 with the higher SNR in the intermediate primary coil group 8', and moving the other coil element 10a.2 to the intermediate secondary coil group 9'. The principle is the same for the elements 11a with mutual coupling in the intermediate secondary coil group 9', using the SNR ranking to select the top two elements 11a.1 and 11a.2, leaving the coil element 11a.2 with the lower SNR in the intermediate secondary coil group 9', and moving the other coil element 11a.1 to the intermediate primary coil group 8'. As a result, no mutual coupling effect exists in either the final primary coil group 8 or the final secondary coil group 9. If the number of coupling loops is greater than 2, coil elements with mutual coupling having an SNR lower than the second highest SNR are removed (not shown), and the coupling effect within each of the primary and secondary groups is completely eliminated. Alternatively, two coil elements with a higher contribution to the SNR are assigned to different groups, and such assignment of two partial coil elements with a higher SNR significantly reduces the coupling effect within each of the primary and secondary groups, so coil elements with mutual coupling having an SNR lower than the second highest SNR can remain in the group. As a result, coil elements with a higher contribution to the SNR, and therefore of higher importance, and with mutual coupling effects within the same group are separated. Thus, if mutual coupling exists between two coil elements, this transition step ensures that there is no longer any mutual coupling within the primary or secondary coil group.If mutual coupling exists between two or more channels, the movement step further minimizes coupling within the primary or secondary coil group, achieving a better SNR.

[0050] Figure 3 schematically shows a method for receiving an electromagnetic induction signal using a high-frequency receiver system according to a preferred embodiment of the present invention.

[0051] In the first step 100, the coil elements 4 of the receiving coil 3 are scanned. These pre-scans provide the coil characteristics, i.e., their contribution to the SNR and coupling state. In the next step 110, the coil elements 4 are ranked according to their SNR and coupling state. Then, in step 120, as shown in Figure 2, the coil elements 4 are grouped into primary coil group 8 and secondary coil group 9.

[0052] In the case of an MRI scan, step 130 checks whether the number of acquisitions is greater than 1. If no (not greater than 1), the MRI signal is received from the coil elements of the primary coil group 140. If yes (greater than 1), it is checked whether the number of acquisitions is odd (150). If no (not odd), the MRI signal is received from the coil elements of the primary coil group and the secondary coil group for each half of the acquisition count 170, respectively. If yes (odd), the MRI signal is received from the coil elements of the primary coil group and the secondary coil group, with one more acquisition from the coil elements of the primary coil group (160).

[0053] As a result, the maximum possible number of coil elements are used to receive the electromagnetic induction signal while improving the SNR.

[0054] Although the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustrations and descriptions should be considered descriptive or illustrative and not limiting. The present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and implemented by those skilled in the art in carrying out the claimed invention, from the examination of the drawings, disclosure and appended claims. In the claims, the words “comprising” do not exclude other components or steps, and the indefinite articles “a” or “an” do not exclude plurality. The mere fact that certain means are described in different dependent claims does not mean that combinations of these means cannot be used advantageously. No reference numeral in the claims should be construed as limiting in scope. Furthermore, for clarity, not all elements in the drawings are given reference numerals. [Explanation of symbols]

[0055] 1. Magnetic Resonance Imaging System 2. Logon Receiver System 3. Receiving coil 4 Coil elements 5. Subjects to testing 6. Control Unit 7 Evaluation Units 8. Primary coil group (PCG) 8' Intermediate Primary Coil Group 9. Secondary coil group (SCG) 9' Intermediate secondary coil group 10. Type A coil element, without coupling. 10a Type A coil element, with coupling to Type A. 10b Type A coil element, coupled with Type B. 10a.1 Type A coil element, coupled with Type A, and maximum SNR 10a.2 Type A coil element, coupling with Type A, and second largest SNR 11. Type B coil element, without coupling. 11a Type B coil element, with coupling to Type B. 11b Type B coil element, coupled with Type A. 11a.1 Type B coil element, coupled with Type B, and maximum SNR 11a.2 Type B coil element, coupling with Type B, and second largest SNR Scan 100 coil elements. The coil elements are ranked according to the 110 SNR, and the coupling state is determined. 120 Group the coil elements into PCG and / or SCG. 130 Determine the number of signal acquisitions (NSA). Receive signals from the coil elements of 140 PCG Determine whether 150 NSAs are odd. 160 Receive signals from the coil elements of PCG and SCG, and receive one extra signal from the coil element of PCG. For each half of the 170 NSA, signals are received from the PCG and SCG coil elements.

Claims

1. A method for selecting a set of coil elements in a high-frequency coil system having multiple coil elements in order to receive a magnetic resonance signal in a region of interest, The steps include determining the signal-to-noise ranking of multiple coil elements for the region of interest, A step of assigning coil elements to a first type A and a second type B based on the determined signal-to-noise ranking, wherein coil elements having a signal-to-noise ratio higher than a predetermined threshold are assigned to the first type A, and coil elements having a signal-to-noise ratio lower than a predetermined threshold are assigned to the second type B. A step of determining the coupling effect of each coil element of the high-frequency coil system with respect to the region of interest, A step of grouping the coil elements assigned to the first type A or the second type B into primary coil groups and secondary coil groups based on the determined coupling effect and signal-to-noise ratio, wherein coil elements of the same type A or B having mutual coupling effects are assigned to at least partially different coil groups. The steps include selecting a coil element from either the primary coil group or the secondary coil group in order to receive the magnetic resonance signal of the region of interest, A method of having.

2. The steps include assigning a first type A coil element without coupling effect, a first type A coil element without coupling effect, and a second type B coil element that couples with a type A coil element to the primary coil group, The steps include assigning a first type A coil element without coupling effect, a second type B coil element without coupling effect, and a second type B coil element that couples with the first type A coil element to the secondary coil group, A step of assigning two identical coil elements of either a first type A or a second type B to different coil groups according to the signal-to-noise ratio, the step of assigning the coil elements having a higher signal-to-noise ratio to the primary coil group and the coil elements having a lower signal-to-noise ratio to the secondary coil group. The method according to claim 1, further comprising:

3. The method according to claim 1 or 2, wherein the high-frequency coil system has at least one flexible receiving coil or at least two rigid receiving coils, each receiving coil having several coil elements, and at least two of the coil elements are arranged so that they at least partially overlap each other during a magnetic resonance imaging scan.

4. Based on the signal-to-noise ranking determined above, the step of excluding coil elements having a signal-to-noise ratio lower than a second predetermined threshold, The step of grouping the remaining coil elements as described in claim 1, A method according to any one of claims 1 to 3, further comprising:

5. The method according to any one of claims 1 to 4, wherein three or more coil elements of the same first type A or second type B having mutual coupling effects are partially assigned to different groups according to the signal-to-noise ratio, the coil elements having the highest signal-to-noise ratio are assigned to the primary coil group, the coil elements having the second highest signal-to-noise ratio are assigned to the secondary coil group, and one or more coil elements having a signal-to-noise ratio lower than the second highest are removed.

6. The method according to any one of claims 1 to 5, further comprising the steps of: selecting the coil element of the primary coil group to receive an electromagnetic induction signal during the magnetic resonance imaging scan when the number of signal acquisitions is 1; and selecting the coil element of the primary coil group for a first acquisition and the coil element of the secondary coil group for a second acquisition different from the first acquisition to receive an electromagnetic induction signal during the magnetic resonance imaging scan when the number of signal acquisitions is more than 1.

7. The method according to any one of claims 1 to 6, further comprising the step of selecting the coil elements of the primary coil group and the secondary coil group to receive the electromagnetic induction signal when the number of signal acquisitions is greater than 1 and odd, and the electromagnetic induction signal is received one more time from the coil elements of the primary coil group than from the secondary coil group, and when the number of signal acquisitions is greater than 1 and even, selecting the coil elements of the primary coil group and the secondary coil group for each half of the number of signal acquisitions, respectively, to receive the electromagnetic induction signal.

8. A magnetic resonance imaging system, A high-frequency coil system having multiple coil elements that receive magnetic resonance signals in a region of interest, An evaluation unit adapted to determine the signal-to-noise ranking of the plurality of coil elements with respect to the region of interest, and to determine the coupling effect of each coil element of the high-frequency coil system with respect to the region of interest, wherein the evaluation unit is further adapted to assign the coil elements to a first type A and a second type B based on the determined signal-to-noise ranking, wherein coil elements having a signal-to-noise ratio higher than a predetermined threshold are assigned to the first type A, and coil elements having a signal-to-noise ratio lower than a predetermined threshold are assigned to the second type B, and the evaluation unit is further adapted to group the coil elements assigned to the first type A or the second type B based on the determined coupling effect and signal-to-noise ratio into primary coil groups and secondary coil groups, wherein the same first type A or second type B coil elements having a mutual coupling effect are at least partially assigned to different coil groups, A control unit adapted to select a coil element from either the primary coil group or the secondary coil group in order to receive the magnetic resonance signal of the region of interest, A magnetic resonance imaging system having the following features.

9. The aforementioned evaluation unit further, A first type A coil element without coupling effect, a second type B coil element without coupling effect, and a first type A coil element that couples with the second type B coil element are assigned to the primary coil group. Assigning a first type A coil element without coupling effect, a second type B coil element without coupling effect, and a second type B coil element that couples with the first type A coil element to the secondary coil group, and Assigning two identical first type A or second type B coil elements having mutual coupling effects to different coil groups according to the signal-to-noise ratio, wherein the coil elements having a higher signal-to-noise ratio are assigned to the primary coil group, and the coil elements having a lower signal-to-noise ratio are assigned to the secondary coil group. A magnetic resonance imaging system according to claim 8, configured to perform the following:

10. The magnetic resonance imaging system according to claim 8 or 9, wherein the high-frequency coil system comprises at least one flexible receiving coil or at least two rigid receiving coils, each receiving coil comprising several coil elements, and at least two of the coil elements are arranged so that they at least partially overlap each other during a magnetic resonance imaging scan.

11. The magnetic resonance imaging system according to any one of claims 8 to 10, wherein the evaluation unit is further adapted to exclude coil elements having a signal-to-noise ratio lower than a second predetermined threshold based on the determined signal-to-noise ranking, and to group the remaining coils according to claim 8.

12. The evaluation unit is further adapted to group the coil elements into a primary coil group and a secondary coil group based on the determined signal-to-noise ranking and coupling effect, wherein three or more coil elements having mutual coupling effects within the same group are partially assigned to different groups according to the signal-to-noise ratio, the coil element having the highest signal-to-noise ratio is assigned to the primary coil group, the coil element having the second highest signal-to-noise ratio is assigned to the secondary coil group, and one or more coil elements having a signal-to-noise ratio lower than the second highest are removed, the magnetic resonance imaging system according to any one of claims 8 to 11.

13. The magnetic resonance imaging system according to any one of claims 8 to 12, wherein the control unit is adapted to select a coil element of the primary coil group to receive the electromagnetic induction signal during the magnetic resonance imaging scan when the number of signal acquisitions is 1, and to select a coil element of the primary coil group for a first acquisition and a coil element of the secondary coil group for a second acquisition different from the first acquisition to receive the electromagnetic induction signal during the magnetic resonance imaging scan when the number of signal acquisitions is more than 1.

14. The magnetic resonance imaging system according to any one of claims 8 to 13, wherein the control unit is adapted to select coil elements from the primary coil group and the secondary coil group to receive the electromagnetic induction signal when the number of signal acquisitions is greater than 1 and odd, so that the electromagnetic induction signal is received one more time from the coil elements of the primary coil group than from the secondary coil group, and when the number of signal acquisitions is greater than 1 and even, to select coil elements from the primary coil group and the secondary coil group for each half of the number of signal acquisitions, respectively, in order to receive the electromagnetic induction signal.

15. A non-temporary computer-readable medium having stored instructions, wherein the execution of the instructions causes a processor to perform the method according to any one of claims 1 to 7.

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