Method for acquiring signals with overlapping receive coils for MR imaging

Abstract

According to the invention, a method for selecting a set of coil elements of a radio frequency coil system (2) having a plurality of coil elements (4) for receiving magnetic resonance signals of a region of interest, the method comprising the following method steps: determining a signal-to-noise ratio ranking of the plurality of coil elements (4) for the region of interest; assigning the coil elements (4) to a first type A and a second type B on the basis of the determined signal-to-noise ratio ranking, coil elements having a signal-to-noise ratio higher than a predetermined threshold being assigned to the type A and coil elements having a signal-to-noise ratio lower than the predetermined threshold being assigned to the type B; determining a coupling effect of each coil element (4) of the radio frequency coil system (2) for the 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) on the basis of the determined coupling effect and the signal-to-noise ratio, coil elements (4) of the same type A or B having a mutual coupling effect with each other being at least partially assigned into different coil groups (8, 9); and selecting the coil elements in the primary coil group (8) or the secondary coil group (9) for receiving the magnetic resonance signals of the region of interest. In this manner, the quality of MR imaging can be improved while avoiding simple exclusion of coil elements (4) that do not provide sufficient information content, but by selecting and combining the coil elements (4) such that the maximum possible number of coil elements (4) are used to receive electromagnetic induction signals while increasing SNR.

Description

Technical Field

[0001] This invention relates to the field of magnetic resonance (MR) imaging, and more particularly to a method for acquiring electromagnetic induction signals using one or more overlapping receiving coils. Background Technology

[0002] In magnetic resonance imaging (MRI), various receiving coils are used to receive electromagnetic induction signals. After these electromagnetic induction signals are converted into digital signals using an analog-to-digital converter (ADC), various images used for diagnosis are reconstructed.

[0003] Magnetic resonance imaging (MRI) has wide clinical applications when used to acquire images of various parts of the body. Subsequently, various receiving coils have been developed for this purpose. With the development of MRI applications, more and more clinical situations involve the simultaneous use of two or more receiving coils, or the use of the same flexible receiving coil across different anatomical structures. In these clinical scenarios using receiving coils, overlap always exists between channels within the coils or between several coils, which leads to coupling and reduces the signal-to-noise ratio (SNR). Consequently, image quality deteriorates. MRI acquisition typically improves the SNR through multiple averaging accumulations, especially when the main magnetic field is relatively low, such as less than or equal to 1.5 T, or when the imaging field of view is relatively small.

[0004] In traditional scanning, the use of identical coil element combinations with coupling effects between overlapping coil elements in different acquisition stages of multiple averaging acquisitions leads to a decrease in SNR. "Coupling effects between overlapping coil elements" refers to the coupling effect between two coil elements arranged relative to another coil element, resulting in a degraded image quality. This occurs if the two coil elements are geometrically overlapping or arranged very close to each other. Overlapping can exist between two different rigid receiving coils or between two coil elements of the same flexible receiving coil.

[0005] This traditional acquisition strategy leads to inaccurate results because it either simply removes channels with low SNR, or simply doesn't use channels with overlapping channels, or uses channels with identical weights. These strategies are also applied to channels with flexible coil coupling. During the acquisition phase, only the same coil element combination pattern is used. These traditional acquisition strategies neither fully utilize the available receive channels nor completely address the coupling effects between some of the utilized channels.

[0006] US2011 / 006 766A1 describes a method for selecting a set of coil elements from a plurality of physical coil elements included in a coil array to perform a magnetic resonance imaging scan. The coil elements are ordered according to a noise sensitivity matrix and calculated information content. Based on this order, the most suitable set of coil elements is selected. Summary of the Invention

[0007] The purpose of this invention is to improve the quality of MR imaging while avoiding simply excluding coil elements that do not transmit sufficient information. Instead, it selects and combines coil elements to maximize the number of coil elements available for receiving electromagnetic induction signals, thereby increasing the signal-to-noise ratio (SNR).

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

[0009] Therefore, according to the present invention, a method is provided for selecting a set of coil elements in a radio frequency coil system having a plurality of coil elements for receiving magnetic resonance signals in a region of interest, wherein the method includes the following steps:

[0010] The signal-to-noise ratio of the plurality of coil elements (4) for the region of interest is determined;

[0011] The coil elements (4) are assigned to a first type A and a second type B based on the determined signal-to-noise ratio (SNR) sorting, wherein coil elements with an SNR higher than a predetermined threshold are assigned to type A, and coil elements with an SNR lower than the predetermined threshold are assigned to type B.

[0012] Determine the coupling effect of each coil element (4) of the radio frequency coil system (2) with respect to the region of interest;

[0013] Based on the determined coupling effect and the signal-to-noise ratio, the coil elements (4) assigned to the first type A or the second type B are grouped into primary coil groups (8) and secondary coil groups (9), wherein coil elements (4) that have mutual coupling effects are at least partially assigned to different coil groups (8, 9); and

[0014] Select the coil element in the primary coil group (8) or the secondary coil group (9) to receive the magnetic resonance signal in the region of interest.

[0015] As further explained above, it is important to group and combine coil elements to ensure that electromagnetic induction signals are received with the highest possible SNR and the maximum possible number of coil elements. In particular, coil elements correspond to coil channels.

[0016] When two or more receiving coils are used to receive data simultaneously, all coil elements available for reception are classified into two types. Coil elements with higher SNR are assigned to type A, and coil elements with lower SNR are assigned to type B. Based on types A and B, the coil elements are divided into two groups: the primary coil group and the secondary coil group.

[0017] The key point of this invention is that coil elements that have mutual coupling effects are at least partially allocated to different coil groups and thus divided.

[0018] Signal-to-noise ratio (SNR) sorting means arranging all coil elements according to their contribution to SNR, from those contributing more to SNR to those contributing less. These coil elements are assigned to type A (higher SNR contribution) and type B (lower SNR contribution) based on predetermined thresholds.

[0019] Typically, mutual coupling occurs between two overlapping elements, such that the partitioning method ensures that the coupling effect between two overlapping coil elements within the same group is significantly reduced or even completely eliminated in each group.

[0020] In particular, the noise correlation matrix and / or coil sensitivity map are used to determine whether there is a coupling effect between two coil elements.

[0021] According to a preferred embodiment of the present invention, the method includes further method steps:

[0022] Type A coil elements without coupling effects, Type B coil elements without coupling effects, and Type A coil elements coupled to Type B coil elements are assigned to the primary coil group.

[0023] Type A coil elements without coupling effects, Type B coil elements without coupling effects, and Type B coil elements coupled to Type A coil elements are assigned to the secondary coil group; and

[0024] Based on the signal-to-noise ratio, two coil elements of the same type A or B with mutual coupling effect are assigned to different coil groups, wherein the coil element with a higher signal-to-noise ratio is assigned to the primary coil group, and the coil element with a lower signal-to-noise ratio is assigned to the secondary coil group.

[0025] The primary coil group includes coil elements of type A, specifically for coil channels that contribute relatively large amounts to the SNR, and the secondary coil group includes coil elements of type B, specifically for coil channels that contribute relatively small amounts to the SNR. Coil elements that have coupling effects with other elements are also identified. Coil elements within the same group that have mutual coupling effects are divided. Therefore, a first coil element and a second coil element are identified among the coil elements with mutual coupling effects 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. "Assignment" preferably refers to a coil element moving from its original group to a corresponding other group. For example, if two coil elements within the primary coil group have mutual coupling effects, the coil element with the higher SNR remains in the primary coil group, and the second coil element moves to the secondary coil group. In this way, coil elements with mutual coupling effects are assigned to different groups and used for different scans. Channels of coils that do not have coupling effects are divided into two coil groups: the primary coil group and the secondary coil group.

[0026] As a result, two coil groups were constructed: a primary coil group and a secondary coil group. The primary coil group includes coil elements with an SNR above a predetermined threshold, thus contributing more to the SNR (type A coil elements), as well as type A and type B coil elements without coupling effects. The secondary coil group includes coil elements with an SNR below a predetermined threshold, thus contributing less to the SNR (type B coil elements), and also includes type A and type B coil elements without coupling. Coupling effects exist between the coil elements in the primary coil group and the coil elements in the secondary coil group, which is acceptable because the coil elements in different groups are used for different scans. As described above, by allocating or rearranging coil elements with higher SNR in the primary coil group and coil elements with lower SNR in the secondary coil group, coil elements with mutual coupling effects within the same coil group (e.g., two coil elements with mutual coupling effects both grouped into the primary coil group) are divided into different coil groups.

[0027] Preferably, the method further includes a method step of pre-scanning the region of interest to determine the signal-to-noise ratio ranking and coupling effects.

[0028] Before starting the actual MRI scan, the coil elements of each receiving coil arrangement are analyzed once using the generated pre-scan data. Based on the pre-scan data, the coil channels are grouped into two groups: a primary coil group and a secondary coil group. Preferably, in a later MRI scan, a portion of the acquisition uses the coil elements of the primary coil group, and another portion uses the coil elements of the secondary coil group, which minimizes the effects of coupling between the channels.

[0029] According to a preferred embodiment of the invention, the radio frequency coil system includes at least one flexible receiving coil or at least two rigid receiving coils, wherein each receiving coil includes several coil elements, and at least two coil elements are arranged such that they at least partially overlap each other during magnetic resonance imaging scans.

[0030] A coil system comprises multiple coils used in combination or a single flexible coil. "Partial overlap" refers to the arrangement of two coil elements relative to another coil element, resulting in a coupling effect between these two overlapping coil elements that degrades image quality. This occurs if the two coil elements are geometrically overlapping or arranged very close to each other. Overlap can exist between two different rigid receiving coils or between two coil elements of the same flexible receiving coil.

[0031] According to a preferred embodiment of the present invention, the method includes the following further method steps:

[0032] Based on the determined signal-to-noise ratio (SNR) ranking, remove the coil elements whose SNR is lower than a second predetermined threshold;

[0033] The remaining coil elements are grouped as described above.

[0034] Specifically, removal means ignoring the coil elements used to receive the magnetic resonance signal. Coil elements with an SNR below the SNR threshold (i.e., the second threshold) are completely removed. Then, based on their contribution to the SNR and coupling effect, all coil elements available for reception are divided into two groups: a primary coil group and a secondary coil group. Specifically, the second threshold is lower than a first predetermined threshold used to divide the coil elements into two groups.

[0035] According to a preferred embodiment of the invention, three or more coil elements of the same type A or B with mutual coupling effects are partially assigned to different groups based on the signal-to-noise ratio (SNR). Thus, the coil element with the highest SNR is assigned to the primary coil group, the coil element with the second highest SNR is assigned to the secondary coil group, and one or more coil elements with lower SNRs are removed. In some cases, such as when very large flexible coils are used for small anatomical structures, and due to folding or mixing the receiving coils into several layers, or when two or more receiving coils are used simultaneously, three or more coupling loops may exist in the same coil group. The element with the highest SNR in the primary coil group is then left in the primary coil group, but the coil element with the second highest SNR is moved to the secondary coil group. Simultaneously, 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 with mutual coupling effects within the same group are removed and not used for scanning. Therefore, the mutual coupling effects caused by overlapping coil elements within the same group are completely eliminated, and the scanning quality is further improved.

[0036] According to a preferred embodiment of the present invention, the method includes the following further method steps:

[0037] If the signal acquisition is performed only once, then the coil element of the primary coil group is selected for receiving the electromagnetically induced signal during the magnetic resonance imaging scan.

[0038] If the number of signal acquisitions is more than one, the coil element of the primary coil group is selected for the first acquisition, and the coil element of the secondary coil group is selected for a second acquisition, different from the first acquisition, to receive the electromagnetic induction signal during the magnetic resonance imaging scan.

[0039] This novel acquisition strategy distributes multiple averaged acquisitions to the primary and secondary coil groups. It ensures that if the number of acquisitions (NSA) is only one, the coil elements of the primary coil group are used to receive electromagnetically induced signals during the MRI scan. If the number of acquisitions is greater than one, the coil elements of the primary coil group are used for the first acquisition, and the coil elements of the secondary coil group are used for the second acquisition to receive electromagnetically induced signals during the MRI scan. In this way, the coil elements of different coil groups are used individually to receive signals, thus avoiding coupling effects between them.

[0040] According to a preferred embodiment of the present invention, the method includes the following further method steps:

[0041] If the number of signal acquisitions is more than once and is odd, then the coil elements of the primary coil group and the secondary coil group are selected to receive the electromagnetic induction signal, wherein the signal is received from the coil elements of the primary coil group one more time than it is received from the secondary coil group.

[0042] If the number of signal acquisitions is more than once and is not odd (even), then the coil elements of the primary coil group and the secondary coil group are selected to receive the electromagnetic induction signal, with each coil group used for half of the number of signal acquisitions.

[0043] In this way, if the signal is acquired twice or more, the number of acquisitions using the primary coil group is equal to the number of acquisitions using the secondary coil group, or one more when using the primary coil group. Compared to conventional cumulative averaging acquisition, the proposed strategy does not increase the total scan time. However, it eliminates the mutual coupling effects caused by the physical overlap between channels due to the simultaneous use of multiple coils or a single flexible coil (whose channels partially overlap). This improves the signal-to-noise ratio.

[0044] The number of signal acquisitions (NSA) is divided into two parts: one part uses the primary coil group to receive the signal (NP), and the other part uses the secondary coil group to receive the signal (NS).

[0045] NSA = NP + NS.

[0046] The coil elements of the primary coil assembly are used for a portion of the NP according to the following formula:

[0047]

[0048] The coil elements of the secondary coil group are used for another part of NS according to the following formula:

[0049]

[0050] Furthermore, according to the present invention, a magnetic resonance imaging system is provided, comprising:

[0051] A radio frequency coil system having multiple coil elements for receiving magnetic resonance signals in a region of interest;

[0052] A radio frequency coil system having multiple coil elements for receiving magnetic resonance signals in a region of interest;

[0053] An evaluation unit is adapted to determine the signal-to-noise ratio 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 RF coil system with respect to the region of interest.

[0054] The evaluation unit is further adapted to group the coil elements into type A and type B based on the determined signal-to-noise ratio (SNR) ranking, wherein coil elements with an SNR higher than a predetermined threshold are grouped into type A, and coil elements with an SNR lower than the predetermined threshold are grouped into type B.

[0055] The evaluation unit is further adapted to group 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 the signal-to-noise ratio, wherein coil elements having mutual coupling effects are assigned to different coil groups.

[0056] A control unit adapted to select coil elements in the primary coil group or the secondary coil group for receiving the magnetic resonance signal in the region of interest.

[0057] The radio frequency coil system includes an evaluation unit and a control unit, which are adapted to group coil elements according to SNR sorting and select coil elements in the appropriate group for receiving magnetic resonance signals, as described above.

[0058] According to a preferred embodiment of the invention, the evaluation unit is further adapted to assign type A coil elements without coupling effects, type B coil elements without coupling effects, and type A coil elements coupled to type B coil elements to the primary coil group.

[0059] Type A coil elements without coupling effects, Type B coil elements without coupling effects, and Type B coil elements coupled to Type A coil elements are assigned to the secondary coil group; and

[0060] Based on the signal-to-noise ratio, two coil elements of the same type A or B with mutual coupling effect are assigned to different coil groups, wherein the coil element with a higher signal-to-noise ratio is assigned to the primary coil group, and the coil element with a lower signal-to-noise ratio is assigned to the secondary coil group.

[0061] Preferably, the control unit is also adapted to pre-scan the region of interest to determine the signal-to-noise ratio ranking and coupling effects.

[0062] According to a preferred embodiment of the invention, the radio frequency coil system includes at least one flexible receiving coil or at least two rigid receiving coils, wherein each receiving coil includes several coil elements, and at least two coil elements are arranged such that they at least partially overlap each other during magnetic resonance imaging scans.

[0063] According to a preferred embodiment of the invention, the evaluation unit is further adapted to remove coil elements with a signal-to-noise ratio lower than a second predetermined threshold based on the determined signal-to-noise ratio sorting, and to group the remaining coils as described above.

[0064] Therefore, the evaluation unit can pre-scan the coil elements, sort them according to their SNR, remove coil elements with a SNR lower than a second predetermined threshold, and group them into primary coil groups and secondary coil groups. The control unit can then select coil elements from each group to receive magnetic resonance signals.

[0065] According to a preferred embodiment of the invention, the evaluation unit is further adapted to group coil elements into primary coil groups and secondary coil groups based on the determined signal-to-noise ratio (SNR) 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 SNR, wherein the coil element with the highest SNR is assigned to the primary coil group, the coil element with the second highest SNR is assigned to the secondary coil group, and one or more coil elements with a lower SNR are removed.

[0066] According to a preferred embodiment of the invention, the control unit is adapted to select the coil element of the primary coil group for receiving the electromagnetic induction signal during the magnetic resonance imaging scan if the number of signal acquisitions is once, and to select the coil element of the primary coil group for a first acquisition if the number of signal acquisitions is more than once, and to select the coil element of the secondary coil group for a second acquisition different from the first acquisition, for receiving the electromagnetic induction signal during the magnetic resonance imaging scan.

[0067] According to a preferred embodiment of the present invention, the control unit is adapted to: if the number of signal acquisitions is greater than once and is odd, select the coil elements of the primary coil group and the secondary coil group for receiving the electromagnetic induction signal, wherein the signal is received from the coil elements of the primary coil group one more time than from the secondary coil group; and if the number of signal acquisitions is greater than once and is even (not odd), select the coil elements of the primary coil group and the secondary coil group for receiving the electromagnetic induction signal, with each coil group used for half of the number of signal acquisitions.

[0068] In magnetic resonance imaging (MRI) data acquisition, signal averaging is typically used to improve signal-to-noise ratio (SNR). According to the preferred embodiment of the invention described above, the acquisition strategy allocates multiple cumulative average acquisitions to the primary and secondary coil groups, ensuring that the primary coil group is used when only one acquisition is performed, and that when the cumulative acquisition is greater than or equal to two, the number of acquisitions using the primary coil group is equal to the number of acquisitions using the secondary coil group, or an additional acquisition is performed when using the primary coil group. Compared to conventional cumulative averaging acquisition, the proposed strategy does not increase the total scan time but eliminates the mutual coupling effect caused by physical overlap between channels due to the simultaneous use of multiple coils or a single flexible coil (whose channels partially overlap). Therefore, this improves the signal-to-noise ratio.

[0069] Furthermore, according to the present invention, a non-transitory computer-readable medium is provided, comprising instructions stored thereon that, when executed on a processor, cause the radio frequency receiver system of an MRI apparatus to perform the methods described above. Attached Figure Description

[0070] These and other aspects of the invention will become apparent and elucidated with reference to the embodiments described below. However, such embodiments do not necessarily represent the full scope of the invention, and therefore the scope of the invention is to be interpreted with reference to the claims and this document.

[0071] In the attached diagram:

[0072] Figure 1 A magnetic resonance imaging system according to a preferred embodiment of the present invention is illustrated schematically;

[0073] Figure 2 The process of grouping coil elements according to a preferred embodiment of the present invention is illustrated schematically;

[0074] Figure 3 A method for receiving electromagnetic induction signals using a radio frequency receiver system according to a preferred embodiment of the present invention is illustrated schematically.

[0075] List of reference numerals

[0076] Magnetic Resonance Imaging System 1

[0077] Radio frequency receiver system 2

[0078] Receiving coil 3

[0079] Coil element 4

[0080] Inspection Item 5

[0081] Control Unit 6

[0082] Assessment Unit 7

[0083] Primary coil assembly (PCG) 8

[0084] Intermediate primary coil group 8'

[0085] Secondary coil group (SCG) 9

[0086] Intermediate secondary coil group 9'

[0087] Type A coil element 10 without coupling

[0088] Type A coil element 10a coupled to type A

[0089] Type A coil element 10b coupled to Type B

[0090] Type A coil element 10a.1 with Type A coupling and the highest SNR.

[0091] Type A coil element 10a.2 coupled to Type A with the second highest SNR.

[0092] Type B coil element 11 without coupling

[0093] Type B coil element 11a coupled to type B

[0094] Coil element 11b of type B coupled to type A

[0095] Type B coil element 11a.1 with the highest SNR coupled to Type B.

[0096] Type B coil element 11a.2 with second highest SNR and coupled to Type B.

[0097] Scan coil element 100

[0098] The coil elements are sorted according to their SNR (Shortness-to-Noise Ratio).

[0099] Determine the coupling state 110

[0100] Group the coil elements into PCG and / or SCG 120

[0101] Determine the number of signal acquisitions (NSA): 130

[0102] Receive signal 140 from the coil element of the PCG

[0103] Determine if the NSA is an odd number 150

[0104] Signals are received from the coil elements of the PCG and SCG.

[0105] PCG 160 more times

[0106] Signals are received from the coil elements of the PCG and SCG.

[0107] Each targeting half of the NSA 170 Detailed Implementation

[0108] Figure 1 A magnetic resonance imaging system 1 according to a preferred embodiment of the present invention is schematically illustrated. The magnetic resonance imaging system 1 includes an MRI apparatus. A subject 5 is arranged within the MRI apparatus. For an MRI scan, the subject is covered by a receiving coil 3 of a radio frequency receiver system 2. The receiving coil 3 is flexible and wound around the subject 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 location of the receiving coil 3. The evaluation unit and the control unit can be integrated into the same unit, which can be implemented by a processor, a set of processors, a computer, or a computing system.

[0109] Figure 2 The grouping scheme of coil element 4 is schematically depicted, in particular as follows: Figure 1 The diagram illustrates a grouping scheme for individual flexible coils 3 with overlapping portions. In the first step, several coil elements 4 of the same receiving coil partially overlap, or several coil elements 4 of different receiving coils arranged to partially overlap. In the next step, the coil elements 4 are sorted according to their contribution to the SNR and then classified into Type A and Type B. Type A coil elements include those that contribute more to the SNR, while Type B coil elements include those that contribute less to the SNR. Furthermore, the coupling effect of the coil elements is determined. There are Type A coil elements 10 without coupling effects, Type A coil elements 10a with the same type of coupling effect, and Type A coil elements 10b with another type of coupling effect. Similarly, there are Type B coil elements 11 without coupling effects, Type B coil elements 11a with the same type of coupling effect, and Type B coil elements 11b with another type of coupling effect. Based on the determined coupling effects, 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 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 SNR is lower 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 without coupling effect are grouped into intermediate primary coil group 8' and intermediate secondary coil group 9'. Figure 2The intermediate primary coil group 8' and intermediate secondary coil group 9' are shown overlapping, and both include coil elements 10 and 11 without any coupling effect.

[0110] In some cases, such as when using very large flexible coils for small anatomical structures, and due to folding or mixing the receiving coils into several layers, or when using two or more receiving coils simultaneously, two or more coupling loops may exist in the same coil group. Then, in the next step, through this "marking coupling," for the mutually coupled elements 10a in the intermediate primary coil group 8', based on SNR sorting, the first two elements 10a.1 and 10a.2 are selected, with coil element 10a.1 having a higher SNR remaining in the intermediate primary coil group 8', and the other element 10a.2 moving to the intermediate secondary coil group 9'. Similarly, for the mutually coupled elements 11a in the intermediate secondary coil group 9', based on SNR sorting, the first two elements 11a.1 and 11a.2 are selected, with element 11a.2 having a lower SNR remaining in the intermediate secondary coil group 9', and the other element 11a.1 moving to the intermediate primary coil group 8'. As a result, there is no longer a mutual coupling effect in the final primary coil group 8 or the final secondary coil group 9. If the number of coupling loops is greater than two, mutually coupled coil elements (not shown) with a lower SNR than the second highest SNR are removed to completely eliminate coupling effects within each of the primary and secondary groups. Alternatively, mutually coupled coil elements with a lower SNR than the second highest SNR can remain in the group, since the two coil elements contributing more to SNR have already been assigned to different groups, and this allocation of the two coil elements with higher SNR has significantly reduced coupling effects within each of the primary and secondary groups. Therefore, coil elements that contribute more to SNR and are therefore more important (including those with mutual coupling effects within the same group) are separated. Thus, if mutual coupling exists between two coil elements, this removal step ensures that mutual coupling within the primary or secondary coil group no longer exists. If mutual coupling exists between more than two channels, the removal step also minimizes coupling within the primary or secondary coil group and also achieves better SNR.

[0111] Figure 3 The illustration depicts a method for receiving electromagnetic induction signals using a radio frequency receiver system according to a preferred embodiment of the present invention.

[0112] In the first step 100, the coil elements 4 of the receiving coil 3 are scanned. These pre-scans are used to obtain coil characteristics, namely their contribution to the SNR and coupling state. In the next step 110, the coil elements 4 are sorted according to the SNR and coupling state. Then, in step 120, the coil elements 4 are grouped into primary coil group 8 and secondary coil group 9, as follows: Figure 2 As shown.

[0113] For MRI scans, in step 130, it is checked whether the number of acquisitions is more than one. If not, MRI signals are received from the coil elements of the primary coil group 140. If so, it is checked whether the number of acquisitions is an odd number 150. If not, MRI signals are received from the coil elements of both the primary and secondary coil groups, with each coil group used for half of the acquisitions 170. If so, the MRI signals are received from the coil elements of both the primary and secondary coil groups one more time than from the primary coil group 160.

[0114] Therefore, the maximum possible number of coil elements is used to receive electromagnetic induction signals, thereby increasing the SNR.

[0115] Although the invention has been detailed and described in the accompanying drawings and the foregoing description, such description is to be considered illustrative or exemplary, not restrictive; the 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 practicing the claimed invention by studying the drawings, the disclosure, and the claims. In the claims, the word "comprising" does not exclude other elements or steps, and the quantifiers "a" or "an" do not exclude a plurality. The fact that certain measures are referenced in mutually different dependent claims does not mean that a combination of these measures cannot be used advantageously. Any reference numerals in the claims should not be construed as limiting the scope. Furthermore, for clarity, not all elements in the drawings are denoted by reference numerals.

Claims

1. A method for selecting a set of coil elements in a radio frequency coil system (2) having a plurality of coil elements (4) for receiving magnetic resonance signals in a region of interest, the method comprising the steps of: The signal-to-noise ratio of the plurality of coil elements (4) for the region of interest is determined; The coil elements (4) are assigned to a first type A and a second type B based on the determined signal-to-noise ratio (SNR) sorting, wherein coil elements with an SNR higher than a predetermined threshold are assigned to type A, and coil elements with an SNR lower than the predetermined threshold are assigned to type B. Determine the coupling effect of each coil element (4) of the radio frequency coil system (2) with respect to the region of interest; Based on the determined coupling effect and the signal-to-noise ratio, the coil elements (4) assigned to the first type A or the second type B are grouped into primary coil groups (8) and secondary coil groups (9), wherein coil elements (4) of the same type A or B that have mutual coupling effects are at least partially assigned to different coil groups (8, 9); and Select the coil element in the primary coil group (8) or the secondary coil group (9) to receive the magnetic resonance signal in the region of interest.

2. The method according to claim 1, further comprising: Type A coil elements (10) without coupling effect, Type B coil elements (11) without coupling effect, and Type A coil elements (10b) coupled with Type B coil elements are assigned to the primary coil group (8). The type A coil element (10) without coupling effect, the type B coil element (11) without coupling effect, and the type B coil element (11b) coupled to the type A coil element are assigned to the secondary coil group (9); and Based on the signal-to-noise ratio, two coil elements (10a, 11a) of the same type A or B with mutual coupling effect are assigned to different coil groups (8, 9), wherein the coil element (10a.1, 11a.1) with a higher signal-to-noise ratio is assigned to the primary coil group (8), and the coil element (10a.2, 11a.2) with a lower signal-to-noise ratio is assigned to the secondary coil group (9).

3. The method according to claim 1 or 2, wherein, The radio frequency coil system (2) includes at least one flexible receiving coil (3) or at least two rigid receiving coils, wherein each receiving coil includes several coil elements (4), and at least two coil elements (4) are arranged such that they at least partially overlap each other during magnetic resonance imaging scans.

4. The method according to any one of claims 1 to 3, further comprising the following steps: Based on the determined signal-to-noise ratio (SNR) sorting, remove coil elements with an SNR lower than a second predetermined threshold; The remaining coil elements are grouped according to claim 1.

5. The method according to any one of claims 1 to 4, wherein, According to the signal-to-noise ratio, three or more coil elements of the same type A or B with mutual coupling effect are partially assigned to different groups, wherein the coil element with the highest signal-to-noise ratio (10a.1, 11a.1) is assigned to the primary coil group (8), the coil element with the second highest signal-to-noise ratio (10a.2, 11a.2) is assigned to the secondary coil group (9), and one or more coil elements with a signal-to-noise ratio lower than the second highest signal-to-noise ratio are removed.

6. The method according to any one of claims 1 to 5, wherein, If the signal acquisition is performed once, then the coil element of the primary coil group (8) is selected for receiving the electromagnetic induction signal during the magnetic resonance imaging scan. If the number of signal acquisitions is more than one, the coil element of the primary coil group (8) is selected for the first acquisition, and the coil element of the secondary coil group (9) is selected for a second acquisition different from the first acquisition, in order to receive the electromagnetic induction signal during the magnetic resonance imaging scan.

7. The method according to any one of claims 1 to 6, wherein, If the number of signal acquisitions is more than once and is odd, then the coil elements of the primary coil group (8) and the secondary coil group (9) are selected to receive the electromagnetic induction signal, wherein the signal is received from the coil elements of the primary coil group (8) one more time than it is received from the secondary coil group (9). If the number of signal acquisitions is more than once and is even, then the coil elements of the primary coil group (8) and the secondary coil group (9) are selected for receiving the electromagnetic induction signal, with each coil group used for half of the number of signal acquisitions.

8. A magnetic resonance imaging system (1), comprising: A radio frequency coil system (2) having multiple coil elements (4) for receiving magnetic resonance signals in the region of interest; An evaluation unit (7) is adapted to determine the signal-to-noise ratio ranking of the plurality of coil elements (4) for the region of interest, and to determine the coupling effect of each coil element (4) of the RF coil system (2) for the region of interest. The evaluation unit (7) is further adapted to assign the coil elements (4) to type A and type B based on the determined signal-to-noise ratio (SNR) ranking, wherein coil elements with an SNR higher than a predetermined threshold are assigned to type A, and coil elements with an SNR lower than the predetermined threshold are assigned to type B. The evaluation unit (7) is also adapted to group the coil elements (4) assigned to the first type A or the second type B into primary coil groups (8) and secondary coil groups (9) based on the determined coupling effect and the signal-to-noise ratio, wherein coil elements (4) of the same type A or B that have mutual coupling effects are at least partially assigned to different coil groups (8, 9). A control unit (6) is adapted to select the coil element (4) in the primary coil group (8) or the secondary coil group (9) for receiving the magnetic resonance signal in the region of interest.

9. The magnetic resonance imaging system (1) according to claim 8, wherein, The evaluation unit (7) is also adapted to: Type A coil elements (10) without coupling effect, Type B coil elements (11) without coupling effect, and Type A coil elements (10b) coupled with Type B coil elements are assigned to the primary coil group (8). The type A coil element (10) without coupling effect, the type B coil element (11) without coupling effect, and the type B coil element (11b) coupled to the type A coil element are assigned to the secondary coil group (9); and Based on the signal-to-noise ratio, two coil elements (10a, 11a) of the same type A or B with mutual coupling effect are assigned to different coil groups (8, 9), wherein the coil element (10a.1, 11a.1) with a higher signal-to-noise ratio is assigned to the primary coil group (8), and the coil element (10a.2, 11a.2) with a lower signal-to-noise ratio is assigned to the secondary coil group (9).

10. The magnetic resonance imaging system (1) according to claim 8 or 9, wherein, The radio frequency coil system (2) includes at least one flexible receiving coil (3) or at least two rigid receiving coils, wherein each receiving coil includes several coil elements (4), and at least two coil elements (4) are arranged such that they at least partially overlap each other during magnetic resonance imaging scans.

11. The magnetic resonance imaging system (1) according to any one of claims 8 to 10, wherein, The evaluation unit (7) is also adapted to remove coil elements with a signal-to-noise ratio lower than a second predetermined threshold based on the determined signal-to-noise ratio sorting, and to group the remaining coils according to claim 8.

12. The magnetic resonance imaging system (1) according to any one of claims 8 to 11, wherein, The evaluation unit (7) is also adapted to group the coil elements (4) into primary coil groups (8) and secondary coil groups (9) based on the determined signal-to-noise ratio (SNR) 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 SNR, wherein the coil element with the highest SNR (10a.1, 11a.1) is assigned to the primary coil group (8), the coil element with the second highest SNR (10a.2, 11a.2) is assigned to the secondary coil group (9), and one or more coil elements with an SNR lower than the second highest SNR are removed.

13. The magnetic resonance imaging system (1) according to any one of claims 8 to 12, wherein, The control unit (6) is adapted to: if the number of signal acquisitions is once, select the coil element (4) of the primary coil group (8) for receiving the electromagnetic induction signal during the magnetic resonance imaging scan; and if the number of signal acquisitions is more than once, select the coil element (4) of the primary coil group (8) for the first acquisition, and select the coil element (4) of the secondary coil group (9) for a second acquisition different from the first acquisition, for receiving the electromagnetic induction signal during the magnetic resonance imaging scan.

14. The magnetic resonance imaging system (1) according to any one of claims 8 to 13, wherein, The control unit (6) is adapted to: if the number of signal acquisitions is more than once and is odd, select the coil element (4) of the primary coil group (8) and the secondary coil group (9) for receiving the electromagnetic induction signal, wherein the signal is received from the coil element (4) of the primary coil group (8) more than once from the secondary coil group (9); and if the number of signal acquisitions is more than once and is even, select the coil element (4) of the primary coil group (8) and the secondary coil group (9) for receiving the electromagnetic induction signal, with each coil group used for half of the number of signal acquisitions.

15. A non-transitory computer-readable medium comprising instructions stored thereon, wherein, The execution of the instructions causes the processor to perform the method according to any one of claims 1 to 7.

Images