JP5508785B2 - Magnetic resonance imaging apparatus and high frequency coil - Google Patents

Description

  The present invention relates to a magnetic resonance imaging apparatus and a high frequency coil.

  A magnetic resonance imaging apparatus is an apparatus that images a subject using a magnetic resonance phenomenon. Specifically, the magnetic resonance imaging apparatus applies a high-frequency magnetic field to a subject placed in a static magnetic field, detects a nuclear magnetic resonance signal emitted from the subject by the application of the high-frequency magnetic field, and generates an image. .

  Such a magnetic resonance imaging apparatus includes a high frequency coil for detecting a nuclear magnetic resonance phenomenon emitted from a subject. In recent years, an array coil in which a plurality of coil elements are combined is widely used as the high-frequency coil (see, for example, Patent Documents 1 to 4). Here, the coil elements used for the array coil include various coils such as a loop coil and an 8-shaped coil (also referred to as a “saddle coil”).

  The characteristics of the array coil differ depending on the type of coil element to be combined. For example, an array coil in which a plurality of loop coils are arranged has a deep sensitivity with respect to the subject and a wide sensitivity in the direction in which the loop coils are arranged. An array coil in which a loop coil is overlapped at the center of an 8-shaped coil has a good S / N ratio, but does not have a wide sensitivity enough to cover the entire abdomen.

  For these reasons, in recent years, it has been studied to combine a plurality of loop coils and one 8-shaped coil for the purpose of producing an array coil having a wide sensitivity and a good SN ratio. Yes.

JP 2003-153878 A JP 2007-21188 A JP 2003-50235 A JP 2003-132308 A

  However, when a plurality of loop coils and one 8-shaped coil are combined, the overlap of the coils increases. As a result, the coupling between the coil elements occurs, resulting in a problem that the SN ratio is reduced.

  The present invention has been made in view of the above, and even when a plurality of loop coils and one 8-shaped coil are combined, decoupling between coil elements can be easily realized. An object is to provide a device and a high-frequency coil.

In order to solve the above-described problems and achieve the object, the present invention is a magnetic resonance imaging apparatus including a high-frequency coil that receives a magnetic resonance signal emitted from a subject placed in a static magnetic field, The high-frequency coil includes a plurality of loop coils arranged side by side in a direction orthogonal to the static magnetic field, and at least two 8-shaped coils arranged at symmetrical positions with respect to straight lines passing through the centers of the plurality of loop coils. Yes, and the position of the coil loop with each 8-shaped coil, a position of the plurality of loop coil loop, each coil having, characterized in that the staggered in the direction of the static magnetic field.

Further, the present invention is a high-frequency coil that receives a magnetic resonance signal emitted from a subject placed in a static magnetic field, the plurality of loop coils arranged in a direction orthogonal to the static magnetic field, and the plurality of loop coils a loop coil possess each and at least two 8-shaped coils arranged in symmetrical positions with respect to a straight line passing through the center, and the position of the coil loop with each 8-shaped coils, each of the plurality of loop coils of The position of the coil loop is shifted in the direction of the static magnetic field .

According to the present invention, even when a plurality of loop coils and one 8-shaped coil are combined, there is an effect that decoupling between coil elements can be easily realized.

FIG. 1 is a diagram illustrating an overall configuration of the MRI apparatus according to the first embodiment. FIG. 2 is a diagram showing an example of the arrangement of coil elements in the receiving RF coil. FIG. 3 is a block diagram showing the relationship between the receiving RF coil, the receiving unit, and the computer system. FIG. 4 is a diagram for explaining a unit of a section selected by the selection circuit. FIG. 5 is a diagram for explaining distribution synthesis of received signals and setting of priorities. FIG. 6 is a diagram for explaining the case of synthesizing the reception signals output from the figure 8 coil. FIG. 7 is a diagram (1) for explaining a modification in the case where four loop coils are arranged in a direction orthogonal to the static magnetic field. FIG. 8 is a diagram (2) for explaining a modification in the case where four loop coils are arranged in a direction orthogonal to the static magnetic field. FIG. 9 is a diagram (3) for explaining a modification in the case where four loop coils are arranged in a direction orthogonal to the static magnetic field.

  Embodiments of a magnetic resonance imaging apparatus and a high-frequency coil according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by the Example shown below. In the embodiments described below, the magnetic resonance imaging apparatus is referred to as “MRI (Magnetic Resonance Imaging) apparatus”, and the nuclear magnetic resonance signal is referred to as “NMR (Nuclear Magnetic Resonance) signal”.

  First, the overall configuration of the MRI apparatus according to the first embodiment will be described. FIG. 1 is a diagram illustrating the overall configuration of the MRI apparatus 100 according to the first embodiment. As shown in FIG. 1, an MRI apparatus 100 includes a static magnetic field magnet 1, a gradient magnetic field coil 2, a gradient magnetic field power source 3, a bed 4, a bed control unit 5, a transmission RF (Radio Frequency) coil 6, a transmission unit 7, and a reception. RF coils 8a and 8b, a receiver 9, a sequence controller 10 and a computer system 20 are provided.

  The static magnetic field magnet 1 is formed in a hollow cylindrical shape, and generates a uniform static magnetic field in the internal space. For example, a permanent magnet or a superconducting magnet is used as the static magnetic field magnet 1.

  The gradient coil 2 is formed in a hollow cylindrical shape and is disposed inside the static magnetic field magnet 1. The gradient magnetic field coil 2 is formed by combining three coils corresponding to the X, Y, and Z axes orthogonal to each other. These three coils generate a gradient magnetic field whose magnetic field intensity varies along each of the X, Y, and Z axes by individually receiving a current supply from the gradient magnetic field power supply 3.

  The gradient magnetic fields of the X, Y, and Z axes generated by the gradient coil 2 correspond to, for example, the readout gradient magnetic field Gr, the phase encoding gradient magnetic field Ge, and the slice selection gradient magnetic field Gs. The readout gradient magnetic field Gr is used for changing the frequency of the NMR signal in accordance with the spatial position. The phase encoding gradient magnetic field Ge is used to change the phase of the NMR signal in accordance with the spatial position. The slice selection gradient magnetic field Gs is used to arbitrarily determine an imaging section.

  The gradient magnetic field power supply 3 supplies a current to the gradient magnetic field coil 2. The couch 4 includes a couchtop 4a on which the subject P is placed. Under the control of the couch controller 5, the couchtop 4a is placed in the cavity of the gradient magnetic field coil 2 with the subject P placed thereon (imaging). Insert into the mouth). Usually, the bed 4 is installed such that the longitudinal direction is parallel to the central axis of the static magnetic field magnet 1. Under the control of the control unit 26, the bed control unit 5 drives the bed 4 to move the top 4a in the longitudinal direction and the vertical direction.

  The transmission RF coil 6 is disposed inside the gradient magnetic field coil 2 and receives a high frequency pulse from the transmission unit 7 to generate a high frequency magnetic field. The transmission unit 7 transmits a high-frequency pulse corresponding to the Larmor frequency to the transmission RF coil 6.

  The reception RF coils 8 a and 8 b are high-frequency coils that are arranged inside the gradient magnetic field coil 2 and receive NMR signals emitted from the subject P due to the influence of the high-frequency magnetic field generated by the transmission RF coil 6. The receiving RF coils 8a and 8b output the received NMR signal to the receiving unit 9 as a received signal.

  Each of the receiving RF coils 8a and 8b is an array coil formed by combining a plurality of coil elements. The receiving RF coil 8a is an abdominal coil attached to the abdominal side of the subject, and the receiving RF coil 8b is a spinal coil attached to the back side of the subject. The reception RF coils 8a and 8b are used at the time of abdominal imaging, and only the reception RF coil 8b is used at the time of spine imaging.

  The receiving unit 9 generates raw digital signal data based on the reception signals output from the receiving RF coils 8 a and 8 b, and transmits the generated raw data to the sequence control unit 10. The receiving unit 9 has a plurality of receiving channels for transmitting raw data. By appropriately connecting this reception channel to a coil element included in the reception RF coils 8a and 8b, a reception signal used for generating an image can be selected.

  The sequence control unit 10 scans the subject P by driving the gradient magnetic field power source 3, the transmission unit 7, and the reception unit 9 based on the sequence execution data transmitted from the computer system 20. Then, when raw data is transmitted from the receiving unit 9 as a result of scanning, the sequence control unit 10 transfers the k-space data to the computer system 20.

  Here, the “sequence execution data” is data for executing imaging based on a predetermined sequence. That is, the sequence execution data includes the strength of the power supplied from the gradient magnetic field power supply 3 to the gradient magnetic field coil 2 and the timing of supplying the power, the strength of the RF signal transmitted from the transmission unit 7 to the transmission RF coil 6 and the RF signal. This is data defining transmission timing, timing at which the receiving unit 9 detects an NMR signal, and the like.

  The computer system 20 performs overall control of the MRI apparatus 100, data collection, image reconstruction, and the like. The computer system 20 particularly includes an interface unit 21, an image reconstruction unit 22, a storage unit 23, an input unit 24, a display unit 25, and a control unit 26.

  The interface unit 21 controls input / output of various signals exchanged with the sequence control unit 10. For example, the interface unit 21 transmits sequence execution data to the sequence control unit 10 and receives raw data from the sequence control unit 10.

  Here, the raw data received by the interface unit 21 includes the slice selection gradient magnetic field Gs generated by the gradient coil 2, the phase encoding gradient magnetic field Ge, and the readout gradient magnetic field Gr in the SE (Slice Encode) direction, PE. The information is stored in the storage unit 23 as k-space data in which spatial frequency information in the (Phase Encode) direction and the RO (Read Out) direction is associated.

  The image reconstruction unit 22 generates spectrum data or image data of a desired nuclear spin in the subject P by performing reconstruction processing such as Fourier transform on the k-space data stored in the storage unit 23.

  The storage unit 23 stores raw data (k-space data) received by the interface unit 21, image data generated by the image reconstruction unit 22, and the like for each subject P.

  The input unit 24 receives various instructions and information input from the operator. As the input unit 24, a pointing device such as a mouse or a trackball, a selection device such as a mode change switch, or an input device such as a keyboard is appropriately used.

  The display unit 25 displays various types of information such as spectrum data or image data under the control of the control unit 26. As the display unit 25, a display device such as a liquid crystal display is appropriately used.

  The control unit 26 controls the entire MRI apparatus 100. Specifically, the control unit 26 has a CPU (Central Processing Unit), a memory, and the like (not shown), and controls the operation of each unit described above by executing various programs based on instructions from the operator. To do.

  The overall configuration of the MRI apparatus 100 according to the first embodiment has been described above. Under such a configuration, in the first embodiment, the receiving RF coil 8b includes, as coil elements, a plurality of loop coils arranged side by side in a direction orthogonal to the static magnetic field, and the centers of the plurality of loop coils. And at least two 8-shaped coils arranged at symmetrical positions with respect to a straight line passing therethrough. FIG. 2 is a diagram showing an example of the arrangement of coil elements in the receiving RF coil 8b.

  As shown in FIG. 2, the receiving RF coil 8b includes 15 loop coils 82a to 82c, 83a to 83c, 84a to 84c, 85a to 85c, and 86a to 86c, and six eight-shaped coils 81a to 81f. And have. In FIG. 2, the vertical direction is the direction of the static magnetic field.

  The loop coils 82a to 82c, the loop coils 83a to 83c, the loop coils 84a to 84c, the loop coils 85a to 85c, and the loop coils 86a to 86c are arranged in such a manner that three loop coils are arranged in a direction orthogonal to the static magnetic field. . Each group of the loop coils 82a to 82c, the loop coils 83a to 83c, the loop coils 84a to 84c, the loop coils 85a to 85c, and the loop coils 86a to 86c are arranged side by side in the direction of the static magnetic field.

  The six 8-shaped coils 81a to 81f are arranged in the direction of the static magnetic field, respectively, and are arranged so as to overlap the approximate center of the loop coils 82a to 82c, 83a to 83c, 84a to 84c, 85a to 85c, and 86a to 86c. Is done.

  Here, each 8-shaped coil is arranged at a symmetrical position with respect to a straight line passing through the center of each of the three loop coils. For example, the figure-shaped coils 81a and 81b are arranged at symmetrical positions with respect to straight lines passing through the centers of the three loop coils 82a to 82c. For example, the figure-shaped coils 81b and 81c are arranged at symmetrical positions with respect to straight lines passing through the centers of the three loop coils 83a to 83c. The other 8-shaped coil and loop coil are similarly arranged.

  In this way, by arranging each 8-shaped coil in a symmetrical position with respect to a straight line passing through the center of each of the three loop coils, the position of the coil loop that each 8-shaped coil has and the three loops are arranged. The position of the coil loop included in each coil is shifted in the direction of the static magnetic field by half the size of the coil loop. Thereby, since the overlap of the coil loop which each 8-shaped coil has and the coil loop which each loop coil has decreases, the decoupling between coil elements is implement | achieved.

  Next, the relationship among the receiving RF coil 8b, the receiving unit 9, and the computer system 20 will be described. FIG. 3 is a block diagram showing the relationship among the receiving RF coil 8b, the receiving unit 9, and the computer system 20. As described above, the receiving unit 9 and the computer system 20 exchange information via the sequence control unit 10, but the illustration of the sequence control unit 10 is omitted here.

  As shown in FIG. 3, the reception RF coil 8 b includes a distribution / synthesis circuit 87. The control unit 26 of the computer system 20 includes a priority order setting unit 26a. The receiving unit 9 includes a selection circuit 9a.

  The distribution synthesis circuit 87 of the reception RF coil 8b generates a plurality of new reception signals by distributing and synthesizing the reception signals received by the loop coil and the 8-shaped coil. The received signal distribution and synthesis performed by the distribution and synthesis circuit 87 will be described in detail later.

  The priority order setting unit 26a of the computer system 20 sets the priority order of the reception signals generated by the distribution / combination circuit 87 according to the imaging part that is the part to be imaged. Specifically, the priority order setting unit 26a specifies an imaging part based on the imaging conditions set at the time of imaging, and sets a priority order according to the specified imaging part. The setting of the priority order performed by the priority order setting unit 26a will be described in detail later.

  The selection circuit 9 a of the reception unit 9 selects a reception signal used for generating an image from the reception signals generated by the distribution / synthesis circuit 87. Specifically, the selection circuit 9a selects the received signal according to the priority set by the priority setting unit 26a.

  Here, selection of the received signal by the selection circuit 9a will be described in detail. First, the selection circuit 9a selects a coil element in a unit called a section, and processes a reception signal received by the selected coil element. FIG. 4 is a diagram for explaining a unit of a section selected by the selection circuit 9a. In FIG. 4, each range surrounded by a dotted line indicates a section selected by the selection circuit 9a.

  As shown in FIG. 4, the selection circuit 9a selects a coil element with a unit obtained by combining two 8-shaped coils and three loop coils as one section. For example, the selection circuit 9a selects a coil element in a unit in which two 8-shaped coils 81a and 81b and three loop coils 82a to 82c are combined.

  As described above, the selection circuit 9a selects the coil element in a unit combining two 8-shaped coils and three loop coils, so that the static magnetic field is arranged in a direction orthogonal to the static magnetic field. The range to be imaged can be set on the basis of the sensitivity area for each of the three arranged loop coils.

  Thereafter, the selection circuit 9a selects a reception signal used for image generation from the reception signals generated by the distribution / synthesis circuit 87 in accordance with the priority set by the priority setting unit 26a.

  Next, reception signal distribution / synthesis performed by the distribution / synthesis circuit 87 of the reception RF coil 8b and priority setting performed by the priority setting unit 26a will be described. FIG. 5 is a diagram for explaining distribution synthesis of received signals and setting of priorities. As shown in FIG. 5, for example, a 0 ° -180 ° hybrid circuit 87a and a 0 ° -90 ° hybrid circuit 87b are provided as the distribution / synthesis circuit 87.

  The 0 ° -180 ° hybrid circuit 87a receives reception signals output from the loop coils 82a and 82c. Then, the 0 ° -180 ° hybrid circuit 87a synthesizes the two input signals as they are, and outputs the synthesized signal as a reception signal S1 from the 0 ° output side. The 0 ° -180 ° hybrid circuit 87a synthesizes signals obtained by shifting the phases of the two input signals by 180 °, and outputs the synthesized signal from the 180 ° output side.

  The 0 ° -90 ° hybrid circuit 87b receives the combined signal output from the 180 ° side of the 0 ° -180 ° hybrid circuit 87a and the received signal output from the loop coil 82b. Then, the 0 ° -90 ° hybrid circuit 87b synthesizes the two input signals as they are, and outputs the synthesized signal as a reception signal S2 from the 0 ° output side. Further, the 0 ° -90 ° hybrid circuit 87b synthesizes signals obtained by shifting the phases of the two input signals by 90 °, and outputs the synthesized signal as a received signal S3 from the 90 ° output side.

  Here, a signal output from the 8-shaped coil 81a is a reception signal S4, and a signal output from the 8-shaped coil 81b is a reception signal S5.

  In this case, the priority order setting unit 26a sets priorities for the reception signals S1 to S5. First, the priority order setting unit 26a specifies an imaging part based on the imaging conditions set at the time of imaging, and sets a priority order according to the specified imaging part.

  Here, the characteristics of each reception signal generated by the distribution / synthesis circuit 87 will be described. First, the reception signals S1 and S2 are shallow in the depth direction with respect to the subject, and the loop coils 82a to 82c are arranged in a line. Have a wide sensitivity. The reception signal S3 is deep in the depth direction with respect to the subject and has a wide sensitivity in the direction in which the loop coils 82a to 82c are arranged. Further, the received signals S4 and S5 have a high S / N ratio near the center of the 8-shaped coils 81a and 81b.

  Therefore, for example, when the imaging region is the abdomen, the priority order setting unit 26a receives the received signal S3 (priority order “1”) and the received signal S2 (priority order) as shown by “BODY” in FIG. “2”), the received signal S1 (priority “3”), the received signal S4 (priority “4”), and the received signal S5 (priority “5”) are set in this order. That is, when the imaging region is the abdomen, the priority order of the received signal having a high sensitivity with respect to the subject is high.

  Further, for example, when the imaging region is the spine, the priority order setting unit 26a receives the reception signal S3 (priority order “1”) and the reception signal S4 (priority order) as shown by “SPINE” in FIG. “2”), the received signal S5 (priority “3”), the received signal S2 (priority “4”), and the received signal S1 (priority “5”) are set in this order. That is, when the imaging site is the spine, the priority order of the received signal with a good S / N ratio near the center with respect to the subject increases.

  In this manner, the priority order setting unit 26a sets the priority order of the received signals so that the most suitable sensitivity can be obtained according to the imaging part that is the part to be imaged.

  For example, when the number of reception channels included in the reception unit 9 is limited, the reception signals output from the 8-shaped coils 81a and 81b may be combined. FIG. 6 is a diagram for explaining the case of synthesizing the reception signals output from the figure 8 coil. As shown in FIG. 6, in this case, the distribution / synthesis circuit 87 includes an addition circuit 87c and a 0 ° -90 ° hybrid circuit 87d in addition to the 0 ° -180 ° hybrid circuit 87a and the 0 ° -90 ° hybrid circuit 87b. It has further.

  Here, the signal output from the 0 ° output side of the 0 ° -180 ° hybrid circuit 87a is the reception signal S11, and the signal output from the 0 ° output side of the 0 ° -90 ° hybrid circuit 87b is the reception signal. S12.

  The adder circuit 87c synthesizes the reception signals output from the 8-shaped coils 81a and 81b. The 0 ° -90 ° hybrid circuit 87d receives a signal output from the 90 ° side of the 0 ° -90 ° hybrid circuit 87b and a reception signal output from the adder circuit 87d. Then, the 0 ° -90 ° hybrid circuit 87d synthesizes the two input signals as they are, and outputs the synthesized signal as a reception signal S13 from the 0 ° output side. The 0 ° -90 ° hybrid circuit 87d synthesizes signals obtained by shifting the phases of the two input signals by 90 °, and outputs the synthesized signal as a received signal S14 from the 90 ° output side.

  In this case, the priority order setting unit 26a sets priorities for the reception signals S11 to S14. First, the priority order setting unit 26a specifies an imaging part based on the imaging conditions set at the time of imaging, and sets a priority order according to the specified imaging part.

  Here, the characteristics of each reception signal generated by the distribution / synthesis circuit 87 will be described. First, the reception signals S11 and S12 are shallow in the depth direction with respect to the subject, and the loop coils 82a to 82c are arranged in a line. Have a wide sensitivity. The received signal S13 is wide in the direction in which the loop coils 82a to 82c are arranged, and has a deep sensitivity near the center of the 8-shaped coils 81a and 81b. The received signal S14 is wide in the direction in which the loop coils 82a to 82c are arranged, and has a high S / N ratio near the center of the 8-shaped coils 81a and 81b.

  Therefore, for example, when the imaging region is the abdomen or the spine, the priority order setting unit 26a receives the received signal S14 (priority level “1”), as shown in “BODY” and “SPINE” in FIG. The priority order is set in the order of the received signal S13 (priority order “2”), the received signal S12 (priority order “3”), and the received signal S11 (priority order “4”). That is, in this case, the priority order of received signals with high sensitivity to a subject and high SN ratio near the center is high.

  Here, the priority order setting unit 26a has been described with respect to the case where the imaging region is specified based on the imaging conditions. However, for example, the type of the reception RF coil used at the time of imaging is detected, and the detected reception RF is detected. The imaging region may be specified based on the type of coil. In this case, for example, when both the reception RF coils 8a and 8b are detected, the priority setting unit 26a identifies the imaging region as the abdomen. Further, when only the reception RF coil 8b is detected, the priority setting unit 26a identifies the imaging region as the spine.

  Further, for example, the priority order setting unit 26a may receive the priority order for each received signal from the operator via the input unit 24, and set the received priority order.

  As described above, in the first embodiment, the receiving RF coil 8b is symmetric with respect to a plurality of loop coils arranged side by side in a direction orthogonal to the static magnetic field and straight lines passing through the centers of the plurality of loop coils. And at least two eight-shaped coils disposed in the. Therefore, according to the first embodiment, even when a plurality of loop coils and one 8-shaped coil are combined, decoupling between coil elements can be easily realized.

  In the first embodiment, the distribution / combination circuit 87 generates a plurality of new reception signals by distributing and combining the reception signals received by the loop coil and the 8-shaped coil. The selection circuit 9a selects a reception signal used for image generation from the reception signals generated by the distribution / synthesis circuit 87. Therefore, according to the first embodiment, the reception signal received by each coil element is converted into a reception signal having various characteristics, and an optimum reception signal is selected according to the imaging region, the purpose of imaging, and the like. be able to.

  In the first embodiment, the priority order setting unit 26a sets the priority order of the reception signals generated by the distribution / combination circuit 87 in accordance with the imaging part that is the part to be imaged. Then, the selection circuit 9a selects a received signal according to the priority set by the priority setting unit 26a. Therefore, according to the first embodiment, it is possible to select an optimal reception signal for each imaging region, and thus it is possible to obtain an image with stable image quality even if the imaging region changes.

  Further, in the first embodiment, the priority order setting unit 26a specifies an imaging part based on the imaging conditions set at the time of imaging, and sets the priority order according to the specified imaging part. Therefore, according to the first embodiment, when a plurality of parts are imaged by one examination, it is possible to automatically select an optimal reception signal for each imaging part.

  In the first embodiment, the priority setting unit 26a detects the type of the high-frequency coil used at the time of imaging, specifies the imaging part based on the detected type of the high-frequency coil, and according to the specified imaging part. Set priority. Therefore, according to the first embodiment, when a plurality of different high-frequency coils are used for imaging, it is possible to automatically select an optimal reception signal for each imaging region.

  In the first embodiment, the case where the three loop coils are arranged in the direction orthogonal to the static magnetic field has been described, but the present invention is not limited to this. For example, the present invention can be similarly applied to a case where four loop coils are arranged in a direction orthogonal to the static magnetic field. 7, 8 and 9 are diagrams for explaining a modification in the case where four loop coils are arranged in a direction orthogonal to the static magnetic field.

  As shown in FIG. 7, for example, the reception RF coil 8b includes 20 loop coils 82d to 82g, 83d to 83g, 84d to 84g, 85d to 85g, and 86d to 86g, and six eight-shaped coils 81a. ~ 81f. In FIG. 7, the vertical direction is the direction of the static magnetic field.

  The loop coils 82d to 82g, the loop coils 83d to 83g, the loop coils 84d to 84g, the loop coils 85d to 85g, and the loop coils 86d to 86g are arranged so that four loop coils are arranged in a direction orthogonal to the static magnetic field. . In addition, each set of the loop coils 82d to 82g, the loop coils 83d to 83g, the loop coils 84d to 84g, the loop coils 85d to 85g, and the loop coils 86d to 86g are arranged side by side in the direction of the static magnetic field.

  Also in this case, the six 8-shaped coils 81a to 81f are arranged in the direction of the static magnetic field, respectively, and are approximately the center of the loop coils 82d to 82g, 83d to 83g, 84d to 84g, 85d to 85g, and 86d to 86g. Are placed on top of each other.

  Here, each 8-shaped coil is disposed at a symmetrical position with respect to a straight line passing through the center of each of the four loop coils. For example, the figure-shaped coils 81a and 81b are arranged at symmetrical positions with respect to straight lines passing through the centers of the four loop coils 82d to 82g. For example, the figure-shaped coils 81b and 81c are arranged at symmetrical positions with respect to straight lines passing through the centers of the four loop coils 83d to 83g. The other 8-shaped coil and loop coil are similarly arranged.

  In this way, by arranging each 8-shaped coil in a symmetrical position with respect to a straight line passing through the center of each of the four loop coils, the position of the coil loop and the four loop coils included in each 8-shaped coil. The position of the coil loop that each has is shifted in the direction of the static magnetic field by half the size of the coil loop. As a result, as in the case where the three loop coils are arranged in a direction orthogonal to the static magnetic field, the overlap between the coil loop of each 8-shaped coil and the coil loop of each loop coil is reduced. Decoupling is realized.

  Therefore, even when the four loop coils are arranged in a direction orthogonal to the static magnetic field, decoupling between the coil elements can be easily realized.

  Further, when the four loop coils are arranged in a direction orthogonal to the static magnetic field, for example, as shown in FIG. 8, as the distribution / synthesis circuit 87, a 0 ° -180 ° hybrid circuit 87e and a 0 ° -90 ° A hybrid circuit 87f, a 0 ° -180 ° hybrid circuit 87g, and a 0 ° -90 ° hybrid circuit 87h are provided.

  Also in this case, as in the example illustrated in FIG. 5, the priority order setting unit 26 a specifies an imaging part based on, for example, imaging conditions set at the time of imaging, and each hybrid circuit according to the specified imaging part. And the priority order of the received signals S21 to S26 output from each 8-shaped loop is set.

  When the number of reception channels included in the reception unit 9 is limited, as shown in FIG. 9, for example, the distribution / synthesis circuit 87 further includes an addition circuit 87i and a 0 ° -90 ° hybrid circuit 87j. . The adder circuit 87i synthesizes the reception signals output from the 8-shaped coils 81a and 81b.

  Also in this case, as in the example illustrated in FIG. 6, the priority order setting unit 26 a specifies an imaging part based on, for example, an imaging condition set at the time of imaging, and each hybrid circuit according to the specified imaging part. The priority order of the received signals S31 to S35 output from is set.

  Thus, even when the four loop coils are arranged in a direction orthogonal to the static magnetic field, the priority order of the received signals is obtained so that the most suitable sensitivity can be obtained according to the imaging part that is the part to be imaged. Set.

100 MRI system (magnetic resonance imaging system)
8b RF coil for reception 82a-82g, 83a-83g, 84a-84g, 85a-85g, 86a-86g, loop coil 81a-81f 8-shaped coil

Claims (7)

A magnetic resonance imaging apparatus comprising a high frequency coil for receiving a magnetic resonance signal emitted from a subject placed in a static magnetic field,
The high-frequency coil is
A plurality of loop coils arranged side by side in a direction orthogonal to the static magnetic field;
Possess a shaped coil of at least two 8 disposed at symmetrical positions with respect to a straight line passing through the center of each of the plurality of loop coils,
A magnetic resonance imaging apparatus , wherein a position of a coil loop included in each of the eight-shaped coils and a position of a coil loop included in each of the plurality of loop coils are shifted in the direction of a static magnetic field . Distributing and synthesizing means for generating a plurality of new received signals by distributing and synthesizing the received signals received by the loop coil and the 8-shaped coil;
The magnetic resonance imaging apparatus according to claim 1, further comprising: a selection unit that selects a reception signal used for generating an image from reception signals generated by the distribution and synthesis unit. In accordance with the imaging part that is the part to be imaged, the apparatus further comprises priority order setting means for setting the priority order of the reception signals generated by the distribution and synthesis means,
The magnetic resonance imaging apparatus according to claim 2, wherein the selection unit selects the reception signal in accordance with the priority set by the priority setting unit.   4. The magnetism according to claim 3, wherein the priority setting unit specifies the imaging part based on an imaging condition set at the time of imaging, and sets the priority according to the specified imaging part. 5. Resonance imaging device.   The priority order setting unit detects a type of a high-frequency coil used at the time of imaging, specifies the imaging part based on the detected type of the high-frequency coil, and sets the priority order according to the specified imaging part. The magnetic resonance imaging apparatus according to claim 3. The position of the coil loop of each 8-shaped coil and the position of the coil loop of each of the plurality of loop coils are shifted in the direction of the static magnetic field by half the size of the coil loop of each loop coil. The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is a magnetic resonance imaging apparatus. A high-frequency coil that receives a magnetic resonance signal emitted from a subject placed in a static magnetic field,
A plurality of loop coils arranged side by side in a direction orthogonal to the static magnetic field;
Possess a shaped coil of at least two 8 disposed at symmetrical positions with respect to a straight line passing through the center of each of the plurality of loop coils,
A high frequency coil , wherein a position of a coil loop included in each of the 8-shaped coils and a position of a coil loop included in each of the plurality of loop coils are shifted in the direction of a static magnetic field .

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