JP4373570B2 - RF coil and magnetic resonance imaging apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an RF coil (radio frequency coil) and a magnetic resonance imaging apparatus, and more particularly to an RF coil using a saddle type coil and a magnetic resonance imaging apparatus using such an RF coil.
[0002]
[Prior art]
In a magnetic resonance imaging apparatus using a high magnetic field of, for example, about 3 T (tesla) as a static magnetic field, RF excitation of a spin to be imaged and spin using an RF coil comprising a combination of two sets of saddle type coils. A magnetic resonance signal generated by the excited spin is received.
[0003]
This type of RF coil has four saddle-type coils 702, 704, 712, and 714, as schematically shown in FIG. The saddle type coils 702, 704, 712, and 714 have the same size, and are assembled so as to form a cylinder as a whole.
[0004]
The saddle type coils 702 and 704 are opposed to each other across the central axis of the cylinder, and constitute one set. The saddle type coils 712 and 714 are opposed to each other across the central axis of the cylinder, and constitute the other set. The opposing directions of the two sets of saddle type coils 702, 704 and 712, 714 are orthogonal.
[0005]
The two sets of saddle type coils 702, 704 and 712, 714 are connected by connecting conductors 706, 708 and 716, 718, respectively, as shown in FIGS. 16 and 17, for example. ing.
[0006]
In each set, the RF power is supplied to the saddle type coils by the power feeding units 710 and 720 in the portions of the connecting conductors 706, 708, 716, and 718, respectively, as shown in development views in FIGS. Power supply by the power supply units 710 and 720 is performed with a phase difference of 90 °, and so-called quadrature drive is performed.
[0007]
Receiving units (not shown) are connected in parallel to the power feeding units 710 and 720, and receive magnetic resonance signals sensed by the saddle type coils for each set. The two received signals have a phase difference of 90 °. By adding these received signals, a received signal with improved SNR (signal-to-noise ratio) is obtained.
[0008]
[Problems to be solved by the invention]
In the RF coil as described above, since the connecting conductor crosses the other set of coil surfaces, mutual interference occurs between the two sets of saddle type coils through electrostatic coupling due to stray capacitance. This mutual interference cannot be ignored by a high magnetic field RF coil in which the frequency of the RF signal is high, and degrades the quality of RF transmission and reception.
[0009]
Accordingly, an object of the present invention is to realize an RF coil having no mutual interference between two sets of saddle type coils, and a magnetic resonance imaging apparatus using such an RF coil.
[0010]
[Means for Solving the Problems]
(1) The invention according to the first aspect for solving the above-described problem is that four saddle-type coils having a generally cylindrical shape as a whole, and perpendicular to the central axis of the cylindrical shape among the four saddle-type coils. A first coaxial cable that connects two coils facing each other in the first direction, and a cylindrical axis that is substantially perpendicular to the cylindrical central axis and the first direction of the four saddle coils. An RF coil comprising a second coaxial cable that connects two coils facing each other in two directions.
[0011]
In the invention from this viewpoint, since the coils constituting the set are connected by the coaxial cable, mutual interference with other sets of coils through the stray capacitance does not occur.
(2) In another aspect of the invention for solving the above-described problem, the saddle type coil is configured such that the mutual induction between two adjacent coils is the same as the mutual induction between the other two coils. The RF coil according to (1), which is characterized.
[0012]
In the invention from this point of view, the mutual induction between the two adjacent coils is the same as the mutual induction between the other two coils, so that the quadrature operation can be performed correctly.
[0013]
(3) In another aspect of the invention for solving the above problem, in the saddle type coil, the area of the overlapping portion between two adjacent coils is the same as the area of the overlapping portion between the other two coils. The RF coil according to (2), which is characterized in that
[0014]
In the invention in this aspect, the area of the overlapping portion between the two adjacent coils is made the same as the area of the overlapping portion between the other two coils, and mutual induction between the two adjacent coils is performed between the other two coils. Since this is the same as the mutual induction, the quadrature operation can be performed correctly.
[0015]
(4) In another aspect of the invention for solving the above-described problem, the saddle type coil is characterized in that an interval between two adjacent coils is the same as an interval between the other two coils ( The RF coil according to 2).
[0016]
In the invention in this aspect, the interval between the two adjacent coils is made the same as the interval between the other two coils so that the mutual induction between the two adjacent coils is the same as the mutual induction between the other two coils. As a result, the quadrature operation can be performed correctly.
[0017]
(5) In another aspect of the invention for solving the above-described problem, the saddle type coil is such that the area of the overlapping portion between two coils adjacent in one direction is the overlapping portion between the other two coils. The RF coil according to (2), wherein an interval between two coils adjacent to each other in a direction opposite to the one direction is the same as an interval between the other two coils. .
[0018]
In the invention of this aspect, the area of the overlapping portion between two coils adjacent in one direction is made the same as the area of the overlapping portion between the other two coils, and the interval between two coils adjacent in the opposite direction is changed to the other. Since the mutual induction between the two coils is the same as the mutual induction between the other two coils, the quadrature operation can be performed correctly. .
[0019]
(6) According to another aspect of the invention for solving the above-mentioned problem, the saddle type coil is characterized in that two adjacent coils can be opened and closed with a gap (4) or ( The RF coil according to 5).
[0020]
In the invention from this viewpoint, since the two adjacent coils can be opened and closed, the object can be easily put in and out of the internal space of the coil.
(7) In another aspect of the invention for solving the above-described problem, the first coaxial cable is provided with a first power feeding unit provided at an end of the first coaxial cable opposite to the coil connection side, Any one of (1) to (6), further comprising a second power feeding portion provided at an end of the second coaxial cable opposite to the coil connection side. It is RF coil as described in above.
[0021]
In the invention in this aspect, since the power feeding portion is provided at the end portion on the opposite side to the coil connection side of the coaxial cable, the degree of freedom in arranging the power feeding portion is increased.
(8) In another aspect of the invention for solving the above-described problem, the first and second power feeding portions are separated from the saddle coil in the cylindrical axial direction ( The RF coil according to 7).
[0022]
In the invention in this aspect, since the power feeding unit is separated from the saddle type coil, interference with the other coil system through the power feeding unit is eliminated.
(9) In another aspect of the invention for solving the above-described problem, a magnetism that forms an image based on a magnetic resonance signal acquired by applying a high-frequency magnetic field to a subject to be imaged under a static magnetic field and a gradient magnetic field. In the resonance imaging apparatus, as an RF coil for performing at least one of the application of the high-frequency magnetic field and the acquisition of the magnetic resonance signal, four saddle coils having a generally cylindrical shape as a whole, and the four saddle types A first coaxial cable that connects two coils facing each other in a first direction perpendicular to the cylindrical central axis of the coils, and the cylindrical central axis of the four saddle coils and the An RF coil having a second coaxial cable that connects two coils facing each other in a second direction substantially perpendicular to the first direction is used. A magnetic resonance imaging apparatus.
[0023]
In the invention from this viewpoint, since the coils constituting the set are connected by the coaxial cable, mutual interference with other sets of coils through the stray capacitance does not occur. As a result, high-quality magnetic resonance imaging can be performed.
[0024]
(10) In another aspect of the invention for solving the above-described problem, the saddle type coil is configured such that the mutual induction between two adjacent coils is the same as the mutual induction between the other two coils. The magnetic resonance imaging apparatus according to (9), which is characterized.
[0025]
In the invention from this point of view, the mutual induction between the two adjacent coils is the same as the mutual induction between the other two coils, so that the quadrature operation can be performed correctly. As a result, high-quality magnetic resonance imaging can be performed.
[0026]
(11) In another aspect of the invention for solving the above problem, in the saddle type coil, the area of the overlapping portion between two adjacent coils is the same as the area of the overlapping portion between the other two coils. (10) The magnetic resonance imaging apparatus according to (10).
[0027]
In the invention in this aspect, the area of the overlapping portion between the two adjacent coils is made the same as the area of the overlapping portion between the other two coils, and mutual induction between the two adjacent coils is performed between the other two coils. Since this is the same as the mutual induction, the quadrature operation can be performed correctly. As a result, high-quality magnetic resonance imaging can be performed.
[0028]
(12) In another aspect of the invention for solving the above-described problem, the saddle type coil is characterized in that an interval between two adjacent coils is the same as an interval between the other two coils ( The magnetic resonance imaging apparatus according to 10).
[0029]
In the invention in this aspect, the interval between the two adjacent coils is made the same as the interval between the other two coils so that the mutual induction between the two adjacent coils is the same as the mutual induction between the other two coils. As a result, the quadrature operation can be performed correctly. As a result, high-quality magnetic resonance imaging can be performed.
[0030]
(13) In another aspect of the invention for solving the above-described problem, the saddle type coil has an overlapping area between two coils adjacent to each other in one direction. The magnetic resonance imaging apparatus according to (10), wherein an interval between two coils adjacent to each other in the direction opposite to the one direction is the same as an interval between the other two coils. It is.
[0031]
In the invention of this aspect, the area of the overlapping portion between two coils adjacent in one direction is made the same as the area of the overlapping portion between the other two coils, and the interval between two coils adjacent in the opposite direction is changed to the other. Since the mutual induction between the two coils is the same as the mutual induction between the other two coils, the quadrature operation can be performed correctly. . As a result, high-quality magnetic resonance imaging can be performed.
[0032]
(14) In another aspect of the invention for solving the above-mentioned problem, the saddle type coil is characterized in that two adjacent coils can be opened and closed with a gap (12) or ( The magnetic resonance imaging apparatus according to 13).
[0033]
In the invention from this viewpoint, since it is possible to open and close between two adjacent coils at an interval, it is easy to put and remove the object into and from the internal space of the coil.
(15) According to another aspect of the invention for solving the above-described problem, the first power feeding unit provided at an end of the first coaxial cable opposite to the connection side of the coil, Any one of (9) to (14), further comprising a second power feeding portion provided at an end of the second coaxial cable opposite to the coil connection side. The magnetic resonance imaging apparatus described in 1.
[0034]
In the invention in this aspect, since the power feeding portion is provided at the end portion on the opposite side to the coil connection side of the coaxial cable, the degree of freedom in arranging the power feeding portion is increased.
(16) In another aspect of the invention for solving the above-described problem, the first and second power feeding portions are separated from the saddle coil in the cylindrical axial direction ( The magnetic resonance imaging apparatus according to 15).
[0035]
In the invention in this aspect, since the power feeding unit is separated from the saddle type coil, interference with the other coil system through the power feeding unit is eliminated.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the magnetic resonance imaging apparatus. This apparatus is an example of an embodiment of the present invention. An example of an embodiment relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0037]
As shown in FIG. 1, the apparatus has a magnet system 100. The magnet system 100 includes a main magnetic field coil unit 102 and a gradient coil unit 106. Each of these coil portions has a substantially cylindrical outer shape and is arranged coaxially.
[0038]
For example, an imaging target 300 in which a body portion is wrapped by an RF coil unit 108 is mounted on a cradle 500 and carried into an internal space of the magnet system 100.
[0039]
The RF coil unit 108 also has a substantially cylindrical outer shape, and is positioned so as to be coaxial with the main magnetic field coil unit 102 and the gradient coil unit 106. The RF coil unit 108 is an example of an embodiment of the RF coil of the present invention. The configuration of the RF coil of the present invention is shown by the configuration of the coil. The RF coil unit 108 will be described later.
[0040]
The main magnetic field coil unit 102 forms a static magnetic field in the internal space of the magnet system 100. The direction of the static magnetic field is generally parallel to the body axis direction of the object 300. That is, a so-called horizontal magnetic field is formed. The main magnetic field coil unit 102 is configured using, for example, a superconducting coil. Needless to say, the present invention may be configured using not only a superconducting coil but also a normal conducting coil.
[0041]
The gradient coil unit 106 generates a gradient magnetic field for giving a gradient to the static magnetic field strength. There are three types of gradient magnetic fields that are generated: a slice gradient magnetic field, a read out gradient magnetic field, and a phase encode gradient magnetic field. The gradient coil unit 106 corresponds to these three types of gradient magnetic fields. Has three gradient coils (not shown).
[0042]
The RF coil unit 108 generates a high-frequency magnetic field for exciting spins in the body of the target 300. Hereinafter, the formation of a high-frequency magnetic field is also referred to as transmission of an RF excitation signal. The RF coil unit 108 also receives an electromagnetic wave generated by excited spin, that is, a magnetic resonance signal.
[0043]
A gradient driving unit 130 is connected to the gradient coil unit 106. The gradient driving unit 130 gives a driving signal to the gradient coil unit 106 to generate a gradient magnetic field. The gradient driving unit 130 includes three systems of driving circuits (not shown) corresponding to the three systems of gradient coils in the gradient coil unit 106.
[0044]
An RF drive unit 140 and a data collection unit 150 are connected to the RF coil unit 108. The RF drive unit 140 provides a drive signal to the RF coil unit 108 and transmits an RF excitation signal to excite spins in the body of the target 300. The data collection unit 150 takes in the magnetic resonance signals received by the RF coil unit 108 and collects them as digital data.
[0045]
A control unit 160 is connected to the gradient driving unit 130, the RF driving unit 140, and the data collection unit 150. The control unit 160 controls the gradient driving unit 130 or the data collection unit 150, respectively.
[0046]
The output side of the data collection unit 150 is connected to the data processing unit 170. The data processing unit 170 stores the data fetched from the data collection unit 150 in a memory (not shown). A data space is formed in the memory. The data space constitutes a two-dimensional Fourier space. The data processing unit 170 reconstructs an image of the target 300 by performing two-dimensional inverse Fourier transform on the data in the two-dimensional Fourier space.
[0047]
The data processing unit 170 is connected to the control unit 160. The data processing unit 170 is above the control unit 160 and controls it. A display unit 180 and an operation unit 190 are connected to the data processing unit 170. The display unit 180 displays the reconstructed image and various information output from the data processing unit 170. The operation unit 190 is operated by an operator and inputs various commands and information to the data processing unit 170.
[0048]
FIG. 2 shows a schematic configuration of the RF coil unit 108. The RF coil unit 108 is an RF coil having a configuration common to that shown in FIG. If it demonstrates again, the RF coil part 108 will have the four saddle type coils 802,804,812,814 as shown in the figure. The saddle type coils 802, 804, 812, and 814 have the same size, and are supported by support means (not shown) so as to form a generally cylindrical shape as a whole. Saddle type coils 802, 804, 812, and 814 are examples of embodiments of the saddle type coil in the present invention. Hereinafter, the saddle type coil is also simply referred to as a coil.
[0049]
The saddle type coils 802 and 804 are opposed to each other across the central axis of the cylinder, and constitute one set. The saddle type coils 812 and 814 are opposed to each other across the central axis of the cylinder, and constitute the other set. The facing direction of one set of saddle type coils and the facing direction of the other set of saddle type coils are orthogonal to each other.
[0050]
The two sets of saddle type coils 802, 804 and 812, 814 are connected by coaxial cables 806, 808 and 816, 818, respectively, for example, as shown in FIGS. The coaxial cables 806 and 808 are an example of an embodiment of the first coaxial cable in the present invention. The coaxial cables 816 and 818 are an example of an embodiment of the second coaxial cable in the present invention. In FIG. 2, the coaxial cables are not shown.
[0051]
An example of the connection state of each pair of coil pairs by a coaxial cable is schematically shown in FIG. 5 and FIG. As shown in FIG. 5, a central conductor and a shield conductor on one end side of the coaxial cable 806 are connected to one end and the other end of a loop of the coil 802, respectively. A central conductor and a shield conductor on one end side of the coaxial cable 808 are connected to one end and the other end of the loop of the coil 804, respectively.
[0052]
On the other end side of the coaxial cables 806 and 808, the shield conductor of the coaxial cable 806 and the center conductor of the coaxial cable 808 are connected, and the power feeding unit 810 is connected between the center conductor of the coaxial cable 806 and the shield conductor of the coaxial cable 808. The The power feeding unit 810 corresponds to the output end of the RF driving unit 140. With such a connection, the coils 802 and 804 are fed in series. The power feeding unit 810 is an example of an embodiment of the first power feeding unit in the present invention.
[0053]
As shown in FIG. 6, the center conductor and the shield conductor on one end side of the coaxial cable 816 are connected to one end and the other end of the loop of the coil 812, respectively. A central conductor and a shield conductor on one end side of the coaxial cable 818 are connected to one end and the other end of the loop of the coil 814, respectively.
[0054]
On the other end side of the coaxial cables 816 and 818, the shield conductor of the coaxial cable 816 and the center conductor of the coaxial cable 818 are connected, and the power feeding unit 820 is connected between the center conductor of the coaxial cable 816 and the shield conductor of the coaxial cable 818. The The power feeding unit 820 corresponds to the output end of the RF driving unit 140. With such a connection, the coils 812 and 814 are fed in series. The power feeding unit 820 is an example of an embodiment of the second power feeding unit in the present invention.
[0055]
As shown in FIG. 7, the coaxial cables 806 and 808 are connected at the other ends of the coaxial cables 806 and 808 with the center conductors and between the shield conductors, respectively. 810 may be connected. With such a connection, the coils 802 and 804 are fed in parallel.
[0056]
Similarly, as shown in FIG. 8, the coaxial cables 816 and 818 are connected to each other between the center conductors and the shield conductors, and power is fed between the center conductor and the shield conductors. The unit 820 may be connected. With such a connection, the coils 802 and 804 are fed in parallel.
[0057]
FIG. 9 shows a development view of two sets of saddle type coils having such a coaxial cable and a feeding portion. Power supply by the power supply units 810 and 820 is performed with a phase difference of 90 °, and so-called quadrature drive is performed.
[0058]
The power supply units 810 and 820 are connected in parallel to the input terminals of the data collection unit 150, and receive magnetic resonance signals sensed by the saddle coils for each set. The two received signals have a phase difference of 90 °. The data collection unit 150 adds the received signals and obtains a received signal with improved SNR by vector synthesis.
[0059]
As shown in FIG. 9, the coaxial cables 806 and 808 cross the coil surface of the coil 814. However, since the coaxial cable has a high degree of external signal shielding, the coil is not affected by the spatial relationship between the two. There is no electrostatic or electromagnetic coupling with 814. The coaxial cables 816 and 818 cross the coil surface of the coil 802, but there is no electrostatic coupling or electromagnetic coupling with the coil 802. For this reason, the interference with the coil of another set originating in the conductor which connects the coils which make a pair does not arise. Therefore, quadrature transmission / reception can be performed correctly. Moreover, the freedom degree of the spatial arrangement | positioning of a coil and the spatial arrangement | positioning of the wiring which connects them increases.
[0060]
In addition, by appropriately determining the lengths of the coaxial cables 806, 808, 816, and 818, the power feeding units 810 and 820 can be installed at appropriate locations separated from the RF coil unit 108, and thus the power feeding units 810 and 820 are provided. The degree of freedom of arrangement increases.
[0061]
The cross section of the cylinder formed by the four saddle coils 802, 804, 812, and 814 may be an ellipse or a shape similar to the cross section of the body portion of the object 300 instead of making it a perfect circle. . By doing so, the distance between each coil and the object 300 is shortened, and the efficiency of RF transmission / reception can be further improved. In the present invention, a cylinder whose section is an ellipse or the like is also a category of a cylinder.
[0062]
When the cross section deviates from a perfect circle, the two sets of saddle type coils are likely to cause interference due to mutual induction. Therefore, in order to cancel such interference, the relationship between the two sets of saddle type coils is defined as shown in FIG. 10, for example. FIG. 10 is a schematic view of the RF coil unit 108 viewed in the axial direction.
[0063]
As shown in the figure, among the four saddle-type coils, two adjacent coils 812 and 804 are arranged so that the coil surfaces partially overlap. The same applies to the remaining two coils 814 and 802. The area of the overlapping part is the same. As a result, the mutual inductance Mab between the coils 812 and 804 is equal to the mutual inductance Mcd between the coils 814 and 802.
[0064]
On the other hand, the ends of adjacent coils 812 and 802 are opposed to each other with a predetermined distance, and the ends of the remaining coils 814 and 804 are also opposed to each other with a predetermined distance. The facing distance is the same. As a result, the mutual inductance Mda between the coils 812 and 802 and the mutual inductance Mbc between the coils 814 and 804 become equal.
[0065]
By defining the mutual relationship in this way, the electromagnetic induction to the coil 804 caused by the current flowing through the coil 812 and the electromagnetic induction to the coil 802 caused by the current flowing through the coil 814 are equal in magnitude and opposite in polarity. Therefore, in the set of the coils 802 and 804, both cancel each other and no influence is produced. The same can be said for the induction from the coil 804 to the coil 812 and the induction from the coil 802 to the coil 814.
[0066]
In addition, the electromagnetic induction to the coil 802 caused by the current flowing in the coil 812 and the electromagnetic induction to the coil 804 caused by the current flowing in the coil 814 are equal in magnitude and opposite in polarity, so that both cancel each other and the coils 802 and 804 Does not affect the group. The same can be said for the induction from the coil 802 to the coil 812 and the induction from the coil 804 to the coil 814.
[0067]
As described above, two sets of saddle type coils can be operated without mutual interference, and quadrature transmission / reception can be performed correctly. Moreover, since the opening area of each coil can be enlarged by comprising as mentioned above, RF transmission / reception can be performed to the deep part in the body of the object 300 with high sensitivity.
[0068]
In order to facilitate the insertion and removal of the target 300, the RF coil unit 108 may be configured to open the upper half on both sides, for example, as shown in FIG. In that case, as shown in FIG. 10, the seam 822 when the upper part is closed as shown by the alternate long and short dash line is, for example, a part where the coil 812 and the coil 802 face each other with a space therebetween. This eliminates the need to provide an electrical connector or the like at the joint. The hinges 824 and 824 ′ on both sides are provided with connectors for maintaining the electrical connection of the coil loop.
[0069]
For example, as shown in FIG. 12, the RF coil unit 108 may be configured to open the upper half to one side. In that case, as shown in FIG. 10, the seam 826 when the upper portion is closed as shown by the alternate long and short dash line is, for example, a portion where the coil 812 and the coil 802 face each other with a gap therebetween. This eliminates the need to provide an electrical connector or the like at the joint. Further, as shown in FIG. 10, the hinge portion 828 at a position symmetrical to the joint is also a portion where the coil 814 and the coil 804 are opposed to each other with a space therebetween, and thus it is necessary to provide an electrical connector or the like. Absent.
[0070]
The photographing operation of this apparatus will be described. FIG. 13 shows an example of a pulse sequence used for imaging. This pulse sequence is a pulse sequence of a gradient echo (GRE) method.
[0071]
That is, (1) is a sequence of α ° pulses for RF excitation in the GRE method, and (2), (3), (4) and (5) are slice gradient Gs, readout gradient Gr, It is a sequence of a phase encoding gradient Gp and a gradient echo MR. The α ° pulse is represented by a center signal. The pulse sequence proceeds from left to right along the time axis t.
[0072]
As shown in the figure, the α ° excitation of the spin is performed by the α ° pulse. The flip angle α ° is 90 ° or less. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed.
[0073]
After the α ° excitation, spin phase encoding is performed by the phase encoding gradient Gp. Next, the spin is first dephased by the readout gradient Gr, and then the spin is rephased to generate a gradient echo MR. The signal intensity of the gradient echo MR becomes maximum at a time point after the echo time TE after the α ° excitation. The gradient echo MR is collected as view data by the data collection unit 150.
[0074]
Such a pulse sequence is repeated 64 to 512 times with a period TR (repetition time). The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 64 to 512 views filling the k space is obtained.
[0075]
Another example of a magnetic resonance imaging pulse sequence is shown in FIG. This pulse sequence is a pulse sequence of a spin echo (SE: Spin Echo) method.
[0076]
That is, (1) is a sequence of 90 ° pulses and 180 ° pulses for RF excitation in the SE method, and (2), (3), (4) and (5) are respectively the slice gradient Gs and the lead. This is a sequence of an out gradient Gr, a phase encode gradient Gp, and a spin echo MR. The 90 ° pulse and the 180 ° pulse are represented by center signals. The pulse sequence proceeds from left to right along the time axis t.
[0077]
As shown in the figure, 90 ° excitation of spin is performed by a 90 ° pulse. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed. After a predetermined time from the 90 ° excitation, 180 ° excitation by a 180 ° pulse, that is, spin inversion is performed. At this time, the slice gradient Gs is applied, and selective inversion is performed for the same slice.
[0078]
In the period between 90 ° excitation and spin reversal, a readout gradient Gr and a phase encode gradient Gp are applied. Spin dephase is performed by the lead-out gradient Gr. Spin phase encoding is performed by the phase encoding gradient Gp.
[0079]
After the spin inversion, the spin is rephased at the readout gradient Gr to generate the spin echo MR. The signal intensity of the spin echo MR becomes maximum at the time after TE from 90 ° excitation. The spin echo MR is collected as view data by the data collection unit 150. Such a pulse sequence is repeated 64 to 512 times with a period TR. The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 64 to 512 views filling the k space is obtained.
[0080]
Note that the pulse sequence used for imaging is not limited to the GRE method or the SE method. For example, the FSE (Fast Spin Echo) method, the fast recovery FSE (Fast Recovery Fast Spin Echo) method, the echo planer imaging (EPI: Echo Planar). Other suitable techniques, such as Imaging).
[0081]
The data processing unit 170 reconstructs a tomographic image of the object 300 by performing two-dimensional inverse Fourier transform on k-space view data. The reconstructed image is stored in the memory and displayed on the display unit 180. There is no mutual interference between the two sets of saddle type coils of the RF coil unit 108, and the quadrature operation is correctly performed, so that a high quality image can be obtained.
[0082]
The above is an example in which the RF coil unit 108 is also used for RF signal transmission / reception, but the RF coil unit 108 may of course be configured separately for RF signal transmission and reception.
[0083]
Further, not only in a quadrature configuration saddle type coil, but also in a so-called phased array coil in which a plurality of coil loops are arranged in parallel, wiring for each coil loop is performed by using a coaxial cable. Mutual interference between the coil loops can be eliminated.
[0084]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to realize an RF coil having no mutual interference between two sets of saddle type coils, and a magnetic resonance imaging apparatus using such an RF coil.
[Brief description of the drawings]
FIG. 1 is a block diagram of an exemplary apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of an RF coil unit in the apparatus shown in FIG.
FIG. 3 is a schematic diagram of a saddle type coil pair constituting the RF coil section shown in FIG. 2;
4 is a schematic diagram of a saddle type coil pair constituting the RF coil section shown in FIG. 2. FIG.
5 is a development view of the saddle type coil pair shown in FIG. 3; FIG.
6 is a development view of the saddle type coil pair shown in FIG. 4; FIG.
7 is a development view of the saddle type coil pair shown in FIG. 3; FIG.
8 is a development view of the saddle type coil pair shown in FIG. 4; FIG.
9 is a development view of the RF coil section shown in FIG. 2. FIG.
10 is a diagram showing the mutual relationship of saddle type coils constituting the RF coil section shown in FIG. 2. FIG.
11 is a view showing an open / closed state of the RF coil section shown in FIG. 2; FIG.
12 is a view showing an open / closed state of the RF coil section shown in FIG. 2;
13 is a diagram showing an example of a pulse sequence executed by the apparatus shown in FIG.
14 is a diagram showing an example of a pulse sequence executed by the apparatus shown in FIG. 1. FIG.
FIG. 15 is a schematic diagram of an RF coil section.
16 is a schematic view of a saddle type coil pair constituting the RF coil section shown in FIG.
FIG. 17 is a schematic diagram of a saddle type coil pair constituting the RF coil section shown in FIG.
18 is a development view of the saddle type coil pair shown in FIG. 16. FIG.
FIG. 19 is a development view of the saddle type coil pair shown in FIG. 17;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 Magnet system 102 Main magnetic field coil part 106 Gradient coil part 108 RF coil part 130 Gradient drive part 140 RF drive part 150 Data collection part 160 Control part 170 Data processing part 180 Display part 190 Operation part 300 Target 500 Cradle 802,804,812 , 814 Saddle coil 806, 808, 816, 818 Coaxial cable 810, 820

Claims (8)

Four saddle-type coils that are generally cylindrical as a whole, and a first coaxial that connects two of the four saddle-type coils that face each other in a first direction perpendicular to the central axis of the cylinder A second coaxial cable that connects two coils facing each other in a second direction substantially perpendicular to the cylindrical central axis and the first direction of the four saddle coils; An RF coil comprising:
In the saddle type coil, the mutual induction between two adjacent coils is the same as the mutual induction between the other two coils,
In the saddle type coil, the interval between two adjacent coils is the same as the interval between the other two coils,
The saddle type coil is capable of opening and closing between two adjacent coils spaced apart from each other. Four saddle-type coils that are generally cylindrical as a whole, and a first coaxial that connects two of the four saddle-type coils that face each other in a first direction perpendicular to the central axis of the cylinder A second coaxial cable that connects two coils facing each other in a second direction substantially perpendicular to the cylindrical central axis and the first direction of the four saddle coils; An RF coil comprising:
In the saddle type coil, the mutual induction between two adjacent coils is the same as the mutual induction between the other two coils,
In the saddle-type coil, the area of the overlapping portion between two coils adjacent in one direction is the same as the area of the overlapping portion between the other two coils, and 2 adjacent in the direction opposite to the one direction. The spacing of one coil is the same as the spacing of the other two coils,
The saddle type coil is capable of opening and closing between two adjacent coils spaced apart from each other.   A first feeding portion provided at an end of the first coaxial cable opposite to the connection side of the coil, and an end of the second coaxial cable opposite to the connection side of the coil; The RF coil according to claim 1, further comprising: a second power feeding unit provided.   4. The RF coil according to claim 3, wherein the first and second feeding portions are separated from the saddle coil in the cylindrical axial direction. 5. In a magnetic resonance imaging apparatus that constructs an image based on a magnetic resonance signal acquired by applying a high-frequency magnetic field to an object to be imaged under a static magnetic field and a gradient magnetic field,
As an RF coil for performing at least one of application of the high-frequency magnetic field and acquisition of the magnetic resonance signal,
Four saddle-type coils that are generally cylindrical as a whole, and a first coaxial that connects two of the four saddle-type coils that face each other in a first direction perpendicular to the central axis of the cylinder A second coaxial cable that connects two coils facing each other in a second direction substantially perpendicular to the cylindrical central axis and the first direction of the four saddle coils; An RF coil comprising:
In the saddle type coil, the mutual induction between two adjacent coils is the same as the mutual induction between the other two coils,
In the saddle type coil, the interval between two adjacent coils is the same as the interval between the other two coils,
2. The magnetic resonance imaging apparatus according to claim 1, wherein the saddle type coil uses an RF coil that can be opened and closed between two adjacent coils with a gap therebetween. In a magnetic resonance imaging apparatus that constructs an image based on a magnetic resonance signal acquired by applying a high-frequency magnetic field to an object to be imaged under a static magnetic field and a gradient magnetic field,
As an RF coil for performing at least one of application of the high-frequency magnetic field and acquisition of the magnetic resonance signal,
Four saddle-type coils that are generally cylindrical as a whole, and a first coaxial that connects two of the four saddle-type coils that face each other in a first direction perpendicular to the central axis of the cylinder A second coaxial cable that connects two coils facing each other in a second direction substantially perpendicular to the cylindrical central axis and the first direction of the four saddle coils; An RF coil comprising:
In the saddle type coil, the mutual induction between two adjacent coils is the same as the mutual induction between the other two coils,
In the saddle-type coil, the area of the overlapping portion between two coils adjacent in one direction is the same as the area of the overlapping portion between the other two coils, and 2 adjacent in the direction opposite to the one direction. The spacing of one coil is the same as the spacing of the other two coils,
2. The magnetic resonance imaging apparatus according to claim 1, wherein the saddle type coil uses an RF coil that can be opened and closed between two adjacent coils with a gap therebetween.   A first feeding portion provided at an end of the first coaxial cable opposite to the connection side of the coil, and an end of the second coaxial cable opposite to the connection side of the coil; The magnetic resonance imaging apparatus according to claim 5, further comprising: a second power feeding unit provided.   The magnetic resonance imaging apparatus according to claim 7, wherein the first and second power feeding units are separated from the saddle coil in the cylindrical axial direction.

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