US20120212225A9 - Magnetic resonance imaging apparatus - Google Patents
Magnetic resonance imaging apparatus Download PDFInfo
- Publication number
- US20120212225A9 US20120212225A9 US13/194,235 US201113194235A US2012212225A9 US 20120212225 A9 US20120212225 A9 US 20120212225A9 US 201113194235 A US201113194235 A US 201113194235A US 2012212225 A9 US2012212225 A9 US 2012212225A9
- Authority
- US
- United States
- Prior art keywords
- coil
- magnetic resonance
- imaging apparatus
- resonance imaging
- loop circuits
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000002595 magnetic resonance imaging Methods 0.000 title claims abstract description 32
- 238000010586 diagram Methods 0.000 description 17
- 238000004088 simulation Methods 0.000 description 7
- 206010040007 Sense of oppression Diseases 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000003292 diminished effect Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
- G01R33/34046—Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils
- G01R33/34076—Birdcage coils
Definitions
- the embodiments described herein relate to a magnetic resonance imaging apparatus having an RF coil.
- An RF coil for sending transmission pulses is installed within a magnetic resonance imaging apparatus.
- the diameter of the RF coil is related to the size of a bore into which a subject is carried. Therefore, the value of the RF coil diameter is very important.
- the bore can be made large by making the RF coil diameter large, thus making it possible to diminish the sense of oppression of a subject when carried into the bore.
- the RF coil diameter is made large, it is required to increase the electric power to be supplied to the RF coil, thus giving rise to the problem that electric power consumption increases.
- an RF shield is disposed around the RF coil, if the RF coil diameter is made large, the spacing between the RF coil and the RF shield becomes narrower.
- the RF shield acts to cancel a magnetic field generated by the RF coil, and the narrower the spacing between the RF coil and the RF shield, the more remarkable the action of the RF shield.
- the narrower the spacing between the RF coil and the RF shield the larger the electric power to be supplied to the RF coil, resulting in a further increase of electric power consumption.
- a magnetic resonance imaging apparatus including: a bore for accommodating a subject; an RF coil disposed around the bore; and an RF shield disposed around the RF coil, the RF coil being constructed such that a portion of the RF coil disposed on a lower surface side of the bore is spaced more distant from the RF shield than a portion of the RF coil disposed on an upper surface side of the bore.
- the RF coil As above it is possible to decrease electric power consumption of the RF coil while ensuring a required size of the bore.
- FIG. 1 is a perspective view showing a magnetic resonance imaging apparatus.
- FIG. 2 is a diagram explaining a positional relation between a birdcage coil 22 and an RF shield 23 .
- FIG. 3 is a diagram showing a state in which the RF shield 23 has been displaced backward with respect to the birdcage coil 22 .
- FIG. 4( a ) and FIG. 4( b ) are diagrams showing the birdcage coil 22 .
- FIG. 5( a ) and FIG. 5( b ) are diagrams explanatory of the shape of the birdcage coil 22 and that of the RF shield 23 .
- FIG. 6( a ) and FIG. 6( b ) are diagrams explanatory of the shape of an upper half Da of a ring D 1 and that of a lower half Db of the ring D 1 .
- FIG. 7( a ) and FIG. 7( b ) are diagrams for explaining an effect obtained by the birdcage coil 22 used in the embodiment.
- FIG. 8 is a graph showing conditions for simulation of an impedance distribution of the birdcage coil 22 .
- FIG. 9 is a diagram showing the result of the simulation.
- FIG. 10 is a diagram showing an example of a ring D 1 having another shape.
- FIG. 1 is a perspective view showing a magnetic resonance imaging apparatus.
- the magnetic resonance imaging apparatus (hereinafter referred to as “MRI apparatus,” MRI: Magnetic Resonance Imaging) indicated at 100 has a magnetic field generator 2 and a table 3 .
- the magnetic field generator 2 is provided with a bore 21 for accommodating a subject.
- a birdcage coil 22 for transmission of RF pulses and reception of magnetic resonance signals from the subject and an RF shield 23 for decreasing RF power radiated outside the MRI apparatus 100 are installed.
- FIG. 2 is a diagram explaining a positional relation between the birdcage coil 22 and the RF shield 23 and FIG. 3 is a diagram showing a state in which the RF shield 23 has been displaced backward with respect to the birdcage coil 22 .
- the magnetic field generator 2 has a coil support 220 for supporting the birdcage coil 22 .
- the coil support 220 is cylindrical, and inside the coil support 220 is mounted a cradle support base 221 for supporting a cradle 31 (see FIG. 1 ) within the bore 21 .
- the space surrounded by the coil support 220 and the cradle support base 221 forms the bore 21 for accommodating the subject.
- the birdcage coil 22 is provided on an outer surface 220 a of the coil support 220 .
- the RF shield 23 is disposed around the birdcage coil 22 .
- FIG. 4( a ) is a perspective view of the birdcage coil 22 and FIG. 4( b ) is a diagram showing which positions legs L 1 to L 16 assume when the birdcage coil 22 is seen from a front side.
- n is set at 16. Therefore, the birdcage coil 22 has sixteen legs L 1 to L 16 .
- the birdcage coil 22 has loop circuits Ci,j.
- Each loop circuit Ci,j is formed using adjacent legs Li, Lj and the rings D 1 , D 2 .
- a loop circuit C 1 , 2 is formed using two adjacent legs L 1 , L 2 and the two rings D 1 , D 2
- a loop circuit C 16 , 1 is formed using two legs L 16 , L 1 and the two rings D 1 , D 2 .
- a route of the loop circuit C 1 , 2 and that of the loop circuit C 16 , 1 are shown schematically using dot-dash lines.
- FIG. 5( a ) is a view of the birdcage coil 22 and the RF shield 22 as shown in FIG. 2 as seen in a z direction and FIG. 5( b ) is a sectional view taken on line A-A in FIG. 5( a ).
- the RF shield 23 has a circular shape when seen in the z direction. More specifically, the RF shield has a circular shape of radius r 1 centered on a reference axis A.
- the ring D 1 of the birdcage coil 22 is constructed so that an upper half Da (a portion positioned on an upper surface 21 a side of the bore 21 ) of the ring D 1 and a lower half Db (a portion positioned on a lower surface 21 b side of the bore 21 ) of the ring D 1 provide an asymmetric shape.
- FIG. 6( a ) is a diagram explanatory of the shape of the upper half Da of the ring D 1 and FIG. 6( b ) is a diagram explanatory of the shape of the lower half Db of the ring Dl.
- the upper half Da of the ring D 1 is indicated with a solid line and the lower half Db of the ring D 1 is indicated with a broken line.
- the upper half Da of the ring D 1 is indicated with a broken line and the lower half Db of the ring D 1 is indicated with a solid line.
- the upper half Da of the ring D 1 has an upper half shape (semi-circular shape) of a circle of radius ra centered on a reference axis A.
- the lower half Db of the ring D 1 has a lower half shape (semi-elliptic shape) of an ellipse having a major axis length of 2ra (twice the ra) and a minor axis length of rb ( ⁇ ra). Therefore, the lower half Db of the ring D 1 is spaced more distant from the RF shield 23 than the upper half Da.
- the lower half Db of the ring D 1 is further spaced a maximum of ⁇ x from the RF shield 23 .
- the ring D 1 is illustrated in FIGS. 6( a ) and 6 ( b ), the other ring D 2 (shown in FIG. 4( a ) also has the same shape as the ring D 1 .
- a lower half (the portion positioned on the lower surface 21 b side of the bore 21 ) 22 b of the birdcage coil 22 is further spaced a maximum of ⁇ x from the RF shield 23 with respect to an upper half (the portion positioned on the upper surface 21 a side of the bore 21 ) 22 a of the birdcage coil 22 .
- FIG. 7( a ) is a diagram showing the RF shield 23 and the birdcage coil 22 having a circular ring DC and FIG. 7( b ) is a diagram showing the RF shield 23 and the birdcage coil 22 having the ring D 1 .
- the larger the coil diameter ra the wider can be the bore 21 , so that the sense of oppression which the subject has within the bore 21 can be diminished.
- the larger the coil diameter ra the smaller the magnetic field generated at the coil center.
- the spacing ⁇ ra between the birdcage coil 22 ′ and the RF shield 23 becomes narrower.
- the RF shield 23 acts to cancel the magnetic field generated by the birdcage coil, and the narrower the spacing ⁇ ra, the more remarkable the action. Therefore, in order to prevent the magnetic field generated at the coil center from becoming small, it is necessary to supply a larger electric power to the birdcage coil 22 ′. As a result, there arises the problem that the electric power consumption increases.
- the lower half 22 b of the birdcage coil 22 is constructed so as to be further spaced a maximum of ⁇ x from the RF shield 23 with respect to the upper half 22 a of the birdcage coil 22 . Therefore, by an amount of ⁇ x, the action of the magnetic field being cancelled by the RF shield 23 can be diminished and hence it is possible to decrease the electric power consumption of the birdcage coil 22 .
- the magnetic field can be made as uniform as possible by adjusting the impedance distribution of the birdcage coil 22 so that the impedance of the upper half 22 a of the birdcage coil 22 becomes high, while the impedance of the lower half 22 b of the birdcage coil 22 becomes low. For example, in connection with the loop circuits Ci,j (see FIG.
- the above impedance distribution can be achieved by making the loop circuits C 1 , 2 to C 8 , 9 high in impedance and the loop circuits C 9 , 10 to C 16 , 1 low in impedance.
- the impedance distribution of the birdcage coil 22 it is possible to enhance the uniformity of the magnetic field.
- simulation has been conducted to verify that the uniformity of the magnetic field can be enhanced by adjusting the impedance distribution. The following description is provided about conditions and result of the simulation.
- FIG. 8 is a graph showing conditions for simulation of the impedance distribution of the birdcage coil 22 .
- the loop circuits Ci,j of the birdcage coil 22 are plotted along the axis of abscissa, while the impedances of the loop circuits Ci,j are plotted along the axis of ordinate.
- the loop circuits C 1 , to C 8 , 9 are set high in impedance, while the loop circuits C 9 , 10 to C 16 , 1 are set low in impedance.
- the impedances are set so that the loop circuits C 4 , 5 and C 5 , 6 located at the highest position are the highest in impedance and the loop circuits C 12 , 13 and C 13 , 14 located at the lowest position are the lowest in impedance.
- FIG. 9 is a diagram showing the result of the simulation.
- the magnetic field strength distribution can be made sufficiently uniform by adjusting like FIG. 8 the impedance distribution of the birdcage coil 22 used in this embodiment.
- the impedance distribution of the birdcage coil 22 can be adjusted for example by adjusting the capacitance and inductance of the birdcage coil 22 .
- the upper half Da of the ring D 1 has a semi-circular shape (see FIG. 6( a ) and the lower half Db of the ring D 1 has a semi-elliptic shape (see FIG. 6( b )).
- the shape of the ring D 1 is not limited to the shape shown in FIGS. 6( a ) and 6 ( b ). It may be another shape. Reference will be made below to an example of a ring D 1 having another shape.
- FIG. 10 is a diagram showing an example of a ring D 1 having another shape.
- An upper half Da of the ring D 1 has a semi-circular shape like the ring D 1 shown in FIGS. 6( a ) and 6 ( b ). However, unlike the ring D 1 shown in FIGS. 6( a ) and 6 ( b ), a lower half Db' of the ring D 1 has a rectilinearly extending portion P. Thus, various changes may be made as to the ring shape of the birdcage coil 22 .
- the RF coil used in the invention may be an RF coil other than the birdcage coil.
Abstract
Description
- This application claims the benefit of Japanese Patent Application No. 2010-169901 filed Jul. 29, 2010, which is hereby incorporated by reference in its entirety.
- The embodiments described herein relate to a magnetic resonance imaging apparatus having an RF coil.
- An RF coil for sending transmission pulses is installed within a magnetic resonance imaging apparatus. The diameter of the RF coil is related to the size of a bore into which a subject is carried. Therefore, the value of the RF coil diameter is very important. The bore can be made large by making the RF coil diameter large, thus making it possible to diminish the sense of oppression of a subject when carried into the bore. However, if the RF coil diameter is made large, it is required to increase the electric power to be supplied to the RF coil, thus giving rise to the problem that electric power consumption increases. Moreover, since an RF shield is disposed around the RF coil, if the RF coil diameter is made large, the spacing between the RF coil and the RF shield becomes narrower. The RF shield acts to cancel a magnetic field generated by the RF coil, and the narrower the spacing between the RF coil and the RF shield, the more remarkable the action of the RF shield. Thus, there arises the problem that the narrower the spacing between the RF coil and the RF shield, the larger the electric power to be supplied to the RF coil, resulting in a further increase of electric power consumption.
- The use of an elliptic RF coil has been proposed as a method for solving the above problem in, for example, Japanese Unexamined Patent Publication No. Hei 7 (1995)-222729.
- However, since the RF coil described in Japanese Unexamined Patent Publication No. Hei 7 (1995)-222729 is elliptic, the coil diameter in the minor axis direction of the ellipse cannot be made large. Accordingly, there is the problem that the bore cannot be made large in the minor axis direction of the ellipse and that therefore a subject who has been carried into the bore is apt to have a sense of oppression.
- The embodiments described herein provide a magnetic resonance imaging apparatus including: a bore for accommodating a subject; an RF coil disposed around the bore; and an RF shield disposed around the RF coil, the RF coil being constructed such that a portion of the RF coil disposed on a lower surface side of the bore is spaced more distant from the RF shield than a portion of the RF coil disposed on an upper surface side of the bore.
- By constructing the RF coil as above it is possible to decrease electric power consumption of the RF coil while ensuring a required size of the bore.
- Further objects and advantages of the embodiments described herein will be apparent from the following description of embodiments of the invention as illustrated in the accompanying drawings.
-
FIG. 1 is a perspective view showing a magnetic resonance imaging apparatus. -
FIG. 2 is a diagram explaining a positional relation between abirdcage coil 22 and anRF shield 23. -
FIG. 3 is a diagram showing a state in which theRF shield 23 has been displaced backward with respect to thebirdcage coil 22. -
FIG. 4( a) andFIG. 4( b) are diagrams showing thebirdcage coil 22. -
FIG. 5( a) andFIG. 5( b) are diagrams explanatory of the shape of thebirdcage coil 22 and that of theRF shield 23. -
FIG. 6( a) andFIG. 6( b) are diagrams explanatory of the shape of an upper half Da of a ring D1 and that of a lower half Db of the ring D1. -
FIG. 7( a) andFIG. 7( b) are diagrams for explaining an effect obtained by thebirdcage coil 22 used in the embodiment. -
FIG. 8 is a graph showing conditions for simulation of an impedance distribution of thebirdcage coil 22. -
FIG. 9 is a diagram showing the result of the simulation. -
FIG. 10 is a diagram showing an example of a ring D1 having another shape. - An embodiment of the invention will be described below, but the invention is not limited to the following embodiment.
-
FIG. 1 is a perspective view showing a magnetic resonance imaging apparatus. - The magnetic resonance imaging apparatus (hereinafter referred to as “MRI apparatus,” MRI: Magnetic Resonance Imaging) indicated at 100 has a
magnetic field generator 2 and a table 3. - The
magnetic field generator 2 is provided with abore 21 for accommodating a subject. Within themagnetic field generator 2, abirdcage coil 22 for transmission of RF pulses and reception of magnetic resonance signals from the subject and anRF shield 23 for decreasing RF power radiated outside theMRI apparatus 100 are installed. -
FIG. 2 is a diagram explaining a positional relation between thebirdcage coil 22 and theRF shield 23 andFIG. 3 is a diagram showing a state in which theRF shield 23 has been displaced backward with respect to thebirdcage coil 22. - The
magnetic field generator 2 has acoil support 220 for supporting thebirdcage coil 22. Thecoil support 220 is cylindrical, and inside thecoil support 220 is mounted acradle support base 221 for supporting a cradle 31 (seeFIG. 1 ) within thebore 21. The space surrounded by thecoil support 220 and thecradle support base 221 forms thebore 21 for accommodating the subject. Thebirdcage coil 22 is provided on anouter surface 220 a of thecoil support 220. TheRF shield 23 is disposed around thebirdcage coil 22. -
FIG. 4( a) is a perspective view of thebirdcage coil 22 andFIG. 4( b) is a diagram showing which positions legs L1 to L16 assume when thebirdcage coil 22 is seen from a front side. - The
birdcage coil 22 has two rings D1, D2 and n number of legs Li (i=1 to n) for connecting the two rings D1 and 2 with each other. In this embodiment, n is set at 16. Therefore, thebirdcage coil 22 has sixteen legs L1 to L16. - The
birdcage coil 22 has loop circuits Ci,j. Each loop circuit Ci,j is formed using adjacent legs Li, Lj and the rings D1, D2. For example, a loop circuit C1,2 is formed using two adjacent legs L1, L2 and the two rings D1, D2, and a loop circuit C16, 1 is formed using two legs L16, L1 and the two rings D1, D2. InFIG. 4( a), a route of the loop circuit C1, 2 and that of the loop circuit C16, 1 are shown schematically using dot-dash lines. - Next, a description will be given below about the shape of the
birdcage coil 22 and that of theRF shield 23. -
FIG. 5( a) is a view of thebirdcage coil 22 and theRF shield 22 as shown inFIG. 2 as seen in a z direction andFIG. 5( b) is a sectional view taken on line A-A inFIG. 5( a). - As shown in
FIG. 5( a), theRF shield 23 has a circular shape when seen in the z direction. More specifically, the RF shield has a circular shape of radius r1 centered on a reference axis A. - On the other hand, the ring D1 of the
birdcage coil 22 is constructed so that an upper half Da (a portion positioned on anupper surface 21 a side of the bore 21) of the ring D1 and a lower half Db (a portion positioned on alower surface 21 b side of the bore 21) of the ring D1 provide an asymmetric shape. -
FIG. 6( a) is a diagram explanatory of the shape of the upper half Da of the ring D1 andFIG. 6( b) is a diagram explanatory of the shape of the lower half Db of the ring Dl. InFIG. 6( a), the upper half Da of the ring D1 is indicated with a solid line and the lower half Db of the ring D1 is indicated with a broken line. On the other hand, inFIG. 6( b), the upper half Da of the ring D1 is indicated with a broken line and the lower half Db of the ring D1 is indicated with a solid line. - As shown in
FIG. 6( a), the upper half Da of the ring D1 has an upper half shape (semi-circular shape) of a circle of radius ra centered on a reference axis A. On the other hand, as shown inFIG. 6( b), the lower half Db of the ring D1 has a lower half shape (semi-elliptic shape) of an ellipse having a major axis length of 2ra (twice the ra) and a minor axis length of rb (<ra). Therefore, the lower half Db of the ring D1 is spaced more distant from theRF shield 23 than the upper half Da. In this embodiment, the upper half Da of the ring D1 is spaced Δra from theRF shield 23, but the lower half Db of the ring D1 is spaced a maximum of Δrb (=Δra+Δx) from theRF shield 23. Thus, the lower half Db of the ring D1 is further spaced a maximum of Δx from theRF shield 23. - Although the ring D1 is illustrated in
FIGS. 6( a) and 6(b), the other ring D2 (shown inFIG. 4( a) also has the same shape as the ring D1. - Therefore, as shown in
FIG. 5( b), a lower half (the portion positioned on thelower surface 21 b side of the bore 21) 22 b of thebirdcage coil 22 is further spaced a maximum of Δx from theRF shield 23 with respect to an upper half (the portion positioned on theupper surface 21 a side of the bore 21) 22 a of thebirdcage coil 22. By thus constructing thebirdcage coil 22 there is obtained an effect that the electric power consumption of thebirdcage coil 22 can be reduced while making the subject-accommodating bore as wide as possible. The reason why this effect is obtained will be explained below with reference toFIGS. 7( a) and 7(b). -
FIG. 7( a) is a diagram showing theRF shield 23 and thebirdcage coil 22 having a circular ring DC andFIG. 7( b) is a diagram showing theRF shield 23 and thebirdcage coil 22 having the ring D1. - In the case of a
birdcage coil 22′ shown inFIG. 7( a), the larger the coil diameter ra, the wider can be thebore 21, so that the sense of oppression which the subject has within thebore 21 can be diminished. However, there is the problem that the larger the coil diameter ra, the smaller the magnetic field generated at the coil center. Moreover, as the coil diameter ra is made larger, the spacing Δra between thebirdcage coil 22′ and theRF shield 23 becomes narrower. TheRF shield 23 acts to cancel the magnetic field generated by the birdcage coil, and the narrower the spacing Δra, the more remarkable the action. Therefore, in order to prevent the magnetic field generated at the coil center from becoming small, it is necessary to supply a larger electric power to thebirdcage coil 22′. As a result, there arises the problem that the electric power consumption increases. - On the other hand, in
FIG. 7( b), thelower half 22 b of thebirdcage coil 22 is constructed so as to be further spaced a maximum of Δx from theRF shield 23 with respect to theupper half 22 a of thebirdcage coil 22. Therefore, by an amount of Δx, the action of the magnetic field being cancelled by theRF shield 23 can be diminished and hence it is possible to decrease the electric power consumption of thebirdcage coil 22. - Since the
lower half 22 b of thebirdcage coil 22 and theupper half 22 a of thebirdcage coil 22 are asymmetric in shape, there sometimes is a case where the uniformity of the magnetic field is disordered. Once the uniformity of the magnetic field is disordered, a bad influence is exerted on the image quality. Therefore, it is desirable that the magnetic field be as uniform as possible. The magnetic field can be made as uniform as possible by adjusting the impedance distribution of thebirdcage coil 22 so that the impedance of theupper half 22 a of thebirdcage coil 22 becomes high, while the impedance of thelower half 22 b of thebirdcage coil 22 becomes low. For example, in connection with the loop circuits Ci,j (seeFIG. 4( b)) of thebirdcage coil 22, the above impedance distribution can be achieved by making the loop circuits C1,2 to C8,9 high in impedance and the loop circuits C9,10 to C16,1 low in impedance. By so adjusting the impedance distribution of thebirdcage coil 22 it is possible to enhance the uniformity of the magnetic field. Next, simulation has been conducted to verify that the uniformity of the magnetic field can be enhanced by adjusting the impedance distribution. The following description is provided about conditions and result of the simulation. -
FIG. 8 is a graph showing conditions for simulation of the impedance distribution of thebirdcage coil 22. - In the graph of
FIG. 8 , the loop circuits Ci,j of thebirdcage coil 22 are plotted along the axis of abscissa, while the impedances of the loop circuits Ci,j are plotted along the axis of ordinate. As shown in the graph ofFIG. 8 , the loop circuits C1, to C8,9 are set high in impedance, while the loop circuits C9,10 to C16,1 are set low in impedance. Particularly, in the simulation conducted this time, the impedances are set so that the loop circuits C4,5 and C5,6 located at the highest position are the highest in impedance and the loop circuits C12, 13 and C13, 14 located at the lowest position are the lowest in impedance. - In
FIG. 7( b), the spacings Δra and Δrb between thebirdcage coil 22 and theRF shield 23 are set so as to satisfy the relationship of Δra :Δrb=1: 2. -
FIG. 9 is a diagram showing the result of the simulation. - In the graph of
FIG. 9 , the position of thebore 21 in AP direction is plotted along the axis of abscissa, while the strength of a magnetic field B1 generated by the birdcage coil is plotted along the axis of ordinate. A solid curve A1 in the graph indicates the strength of a magnetic field B1 generated by theconventional birdcage coil 22′ shown inFIG. 7( a), while a dot-dash line curve A2 in the graph indicates the strength of a magnetic field B1 generated by thebirdcage coil 22 according to this embodiment which has the impedance distribution shown inFIG. 8 . Comparison between both curves A1 and A2 shows that there are obtained almost the same magnetic field strengths. Thus, it is seen that the magnetic field strength distribution can be made sufficiently uniform by adjusting likeFIG. 8 the impedance distribution of thebirdcage coil 22 used in this embodiment. The impedance distribution of thebirdcage coil 22 can be adjusted for example by adjusting the capacitance and inductance of thebirdcage coil 22. - In the
birdcage coil 22 according to this embodiment, the upper half Da of the ring D1 has a semi-circular shape (seeFIG. 6( a) and the lower half Db of the ring D1 has a semi-elliptic shape (seeFIG. 6( b)). However, the shape of the ring D1 is not limited to the shape shown inFIGS. 6( a) and 6(b). It may be another shape. Reference will be made below to an example of a ring D1 having another shape. -
FIG. 10 is a diagram showing an example of a ring D1 having another shape. - An upper half Da of the ring D1 has a semi-circular shape like the ring D1 shown in
FIGS. 6( a) and 6(b). However, unlike the ring D1 shown inFIGS. 6( a) and 6(b), a lower half Db' of the ring D1 has a rectilinearly extending portion P. Thus, various changes may be made as to the ring shape of thebirdcage coil 22. - Although in the above embodiment there is shown an example of using the
birdcage coil 22 as the RF coil, the RF coil used in the invention may be an RF coil other than the birdcage coil. - Many widely different embodiments of the invention may be configured without departing from the spirit and the scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.
Claims (20)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2010169901A JP5248557B2 (en) | 2010-07-29 | 2010-07-29 | Magnetic resonance imaging system |
JP2010-169901 | 2010-07-29 |
Publications (3)
Publication Number | Publication Date |
---|---|
US20120025833A1 US20120025833A1 (en) | 2012-02-02 |
US20120212225A9 true US20120212225A9 (en) | 2012-08-23 |
US8749235B2 US8749235B2 (en) | 2014-06-10 |
Family
ID=45526080
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US13/194,235 Active 2032-07-09 US8749235B2 (en) | 2010-07-29 | 2011-07-29 | Birdcage coil for magnetic resonance imaging apparatus |
Country Status (3)
Country | Link |
---|---|
US (1) | US8749235B2 (en) |
JP (1) | JP5248557B2 (en) |
CN (1) | CN102401886B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11061090B2 (en) | 2017-11-08 | 2021-07-13 | Canon Medical Systems Corporation | Magnetic resonance imaging apparatus and RF coil |
Families Citing this family (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9075119B2 (en) * | 2009-09-30 | 2015-07-07 | Hitachi Medical Corporation | Gradient magnetic field coil and magnetic resonance imaging device |
KR101505331B1 (en) | 2010-07-01 | 2015-03-23 | 바이엘 메디컬 케어 인크. | Multi-channel endorectal coils and interface devices therefor |
JP5555081B2 (en) * | 2010-07-20 | 2014-07-23 | 株式会社日立メディコ | Magnetic resonance imaging system |
CN103777160B (en) * | 2012-10-25 | 2017-03-01 | 西门子股份有限公司 | The body coil of MR imaging apparatus and use its MR imaging apparatus |
JP6533513B2 (en) * | 2013-03-28 | 2019-06-19 | コーニンクレッカ フィリップス エヌ ヴェKoninklijke Philips N.V. | Multi-zone radio frequency coil array for variable patient size |
CN107076812B (en) * | 2014-10-16 | 2019-11-01 | 皇家飞利浦有限公司 | MRI birdcage coil with distribution excitation |
DE102016108601A1 (en) * | 2016-05-10 | 2017-11-16 | Axel Muntermann | Apparatus for nuclear magnetic resonance therapy |
JP7250476B2 (en) * | 2017-11-08 | 2023-04-03 | キヤノンメディカルシステムズ株式会社 | Magnetic resonance imaging device and RF coil |
EP3527999B1 (en) * | 2018-02-16 | 2024-03-27 | Siemens Healthineers AG | Transmitting antenna for a magnetic resonance device |
EP3801244A4 (en) * | 2018-06-11 | 2022-03-09 | Children's Hospital Medical Center | Asymmetric birdcage coil for a magnetic resonance imaging (mri) |
US11275133B2 (en) | 2018-06-11 | 2022-03-15 | Children's Hospital Medical Center | Asymmetric birdcage coil |
US10684336B2 (en) * | 2018-10-24 | 2020-06-16 | General Electric Company | Radiofrequency coil and shield in magnetic resonance imaging method and apparatus |
CN110687487A (en) * | 2019-09-30 | 2020-01-14 | 东软医疗系统股份有限公司 | Large coil, manufacturing method thereof and scanning equipment |
Citations (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4594566A (en) * | 1984-08-30 | 1986-06-10 | Advanced Nmr Systems, Inc. | High frequency rf coil for NMR device |
US4746866A (en) * | 1985-11-02 | 1988-05-24 | U.S. Philips Corporation | High-frequency coil system for a magnetic resonance imaging apparatus |
US4751464A (en) * | 1987-05-04 | 1988-06-14 | Advanced Nmr Systems, Inc. | Cavity resonator with improved magnetic field uniformity for high frequency operation and reduced dielectric heating in NMR imaging devices |
US4939465A (en) * | 1985-06-22 | 1990-07-03 | Bruker Medizintechnik Gmbh | Probe head for nuclear magnetic resonance (NMR) measurements, in particular for use in NMR tomography |
US5543711A (en) * | 1994-11-22 | 1996-08-06 | Picker International, Inc. | Multiple quadrature volume coils for magnetic resonance imaging |
US5557247A (en) * | 1993-08-06 | 1996-09-17 | Uab Research Foundation | Radio frequency volume coils for imaging and spectroscopy |
US6029082A (en) * | 1997-11-24 | 2000-02-22 | Picker International, Inc. | Less-claustrophobic, quadrature, radio-frequency head coil for nuclear magnetic resonance |
US6043658A (en) * | 1997-01-23 | 2000-03-28 | U.S. Philips Corporation | MR apparatus including an MR coil system |
US6462636B1 (en) * | 1999-11-09 | 2002-10-08 | Koninklijke Philips Electronics N.V. | MR apparatus |
US20020165447A1 (en) * | 2001-04-17 | 2002-11-07 | Boskamp Ed B. | Switchable field of view apparatus and method for magnetic resonance imaging |
US20030020476A1 (en) * | 2001-07-20 | 2003-01-30 | Duensing G. Randy | Method and apparatus for magnetic resonance imaging |
US20030122546A1 (en) * | 2001-11-21 | 2003-07-03 | Leussler Christoph Guenther | RF coil system for a magnetic resonance imaging apparatus |
US6591128B1 (en) * | 2000-11-09 | 2003-07-08 | Koninklijke Philips Electronics, N.V. | MRI RF coil systems having detachable, relocatable, and or interchangeable sections and MRI imaging systems and methods employing the same |
US6608480B1 (en) * | 2002-09-30 | 2003-08-19 | Ge Medical Systems Global Technology Company, Llc | RF coil for homogeneous quadrature transmit and multiple channel receive |
US6958607B2 (en) * | 2000-07-31 | 2005-10-25 | Regents Of The University Of Minnesota | Assymetric radio frequency transmission line array |
US7135864B1 (en) * | 2005-07-20 | 2006-11-14 | General Electric Company | System and method of elliptically driving an MRI Coil |
US7495443B2 (en) * | 2003-11-18 | 2009-02-24 | Koninklijke Philips Electronics N.V. | RF coil system for super high field (SHF) MRI |
US7501823B2 (en) * | 2006-04-19 | 2009-03-10 | Siemens Aktiengesellschaft | Cylindrical magnetic resonance antenna |
US7683623B2 (en) * | 2005-06-16 | 2010-03-23 | Koninklijke Philips Electronics N.V. | RF volume coil with selectable field of view |
US7714577B2 (en) * | 2005-10-18 | 2010-05-11 | Tursiop Technologies Llc | Method and apparatus for high-gain magnetic resonance imaging |
US8030930B2 (en) * | 2008-01-29 | 2011-10-04 | Siemens Aktiengesellschaft | Magnetic resonance imaging local coil composed of separate parts |
US8035384B2 (en) * | 2008-10-23 | 2011-10-11 | General Electric Company | Hybrid birdcage-TEM radio frequency (RF) coil for multinuclear MRI/MRS |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3100642B2 (en) * | 1991-01-16 | 2000-10-16 | 株式会社東芝 | Magnetic resonance imaging equipment |
JP3372099B2 (en) | 1994-02-14 | 2003-01-27 | 株式会社日立メディコ | RF probe |
US5760583A (en) | 1996-03-13 | 1998-06-02 | Ge Yokogawa Medical Systems, Limited | RF coil for MRI and MRI apparatus |
US6011393A (en) * | 1997-06-26 | 2000-01-04 | Toshiba America Mri, Inc. | Self-supporting RF coil for MRI |
US6348794B1 (en) | 2000-01-18 | 2002-02-19 | Ge Yokogawa Medical Systems, Limited | RF coil for magnetic resonance imaging having three separate non-overlapping coils electrically isolated from each other |
JP2001198100A (en) | 2000-01-20 | 2001-07-24 | Ge Medical Systems Global Technology Co Llc | Mr data gathering method, mr image display method and mri device |
US7345481B2 (en) * | 2003-11-18 | 2008-03-18 | Koninklijke Philips Electronics N.V. | Hybrid TEM/birdcage coil for MRI |
JP4427475B2 (en) | 2005-04-01 | 2010-03-10 | ジーイー・メディカル・システムズ・グローバル・テクノロジー・カンパニー・エルエルシー | MRI apparatus and auxiliary coil |
WO2007109426A1 (en) * | 2006-03-22 | 2007-09-27 | Koninklijke Philips Electronics, N.V. | Shielded multix coil array for parallel high field mri |
RU2491568C2 (en) * | 2007-02-26 | 2013-08-27 | Конинклейке Филипс Электроникс, Н.В. | Double-resonant radio frequency strong field surface coils for magnetic resonance |
-
2010
- 2010-07-29 JP JP2010169901A patent/JP5248557B2/en active Active
-
2011
- 2011-07-29 US US13/194,235 patent/US8749235B2/en active Active
- 2011-07-29 CN CN201110238486.9A patent/CN102401886B/en not_active Expired - Fee Related
Patent Citations (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4594566A (en) * | 1984-08-30 | 1986-06-10 | Advanced Nmr Systems, Inc. | High frequency rf coil for NMR device |
US4939465A (en) * | 1985-06-22 | 1990-07-03 | Bruker Medizintechnik Gmbh | Probe head for nuclear magnetic resonance (NMR) measurements, in particular for use in NMR tomography |
US4746866A (en) * | 1985-11-02 | 1988-05-24 | U.S. Philips Corporation | High-frequency coil system for a magnetic resonance imaging apparatus |
US4751464A (en) * | 1987-05-04 | 1988-06-14 | Advanced Nmr Systems, Inc. | Cavity resonator with improved magnetic field uniformity for high frequency operation and reduced dielectric heating in NMR imaging devices |
US5557247A (en) * | 1993-08-06 | 1996-09-17 | Uab Research Foundation | Radio frequency volume coils for imaging and spectroscopy |
US5543711A (en) * | 1994-11-22 | 1996-08-06 | Picker International, Inc. | Multiple quadrature volume coils for magnetic resonance imaging |
US6043658A (en) * | 1997-01-23 | 2000-03-28 | U.S. Philips Corporation | MR apparatus including an MR coil system |
US6029082A (en) * | 1997-11-24 | 2000-02-22 | Picker International, Inc. | Less-claustrophobic, quadrature, radio-frequency head coil for nuclear magnetic resonance |
US6462636B1 (en) * | 1999-11-09 | 2002-10-08 | Koninklijke Philips Electronics N.V. | MR apparatus |
US6958607B2 (en) * | 2000-07-31 | 2005-10-25 | Regents Of The University Of Minnesota | Assymetric radio frequency transmission line array |
US6591128B1 (en) * | 2000-11-09 | 2003-07-08 | Koninklijke Philips Electronics, N.V. | MRI RF coil systems having detachable, relocatable, and or interchangeable sections and MRI imaging systems and methods employing the same |
US20020165447A1 (en) * | 2001-04-17 | 2002-11-07 | Boskamp Ed B. | Switchable field of view apparatus and method for magnetic resonance imaging |
US20030020476A1 (en) * | 2001-07-20 | 2003-01-30 | Duensing G. Randy | Method and apparatus for magnetic resonance imaging |
US20030122546A1 (en) * | 2001-11-21 | 2003-07-03 | Leussler Christoph Guenther | RF coil system for a magnetic resonance imaging apparatus |
US6608480B1 (en) * | 2002-09-30 | 2003-08-19 | Ge Medical Systems Global Technology Company, Llc | RF coil for homogeneous quadrature transmit and multiple channel receive |
US7495443B2 (en) * | 2003-11-18 | 2009-02-24 | Koninklijke Philips Electronics N.V. | RF coil system for super high field (SHF) MRI |
US7683623B2 (en) * | 2005-06-16 | 2010-03-23 | Koninklijke Philips Electronics N.V. | RF volume coil with selectable field of view |
US7135864B1 (en) * | 2005-07-20 | 2006-11-14 | General Electric Company | System and method of elliptically driving an MRI Coil |
US7714577B2 (en) * | 2005-10-18 | 2010-05-11 | Tursiop Technologies Llc | Method and apparatus for high-gain magnetic resonance imaging |
US7501823B2 (en) * | 2006-04-19 | 2009-03-10 | Siemens Aktiengesellschaft | Cylindrical magnetic resonance antenna |
US8030930B2 (en) * | 2008-01-29 | 2011-10-04 | Siemens Aktiengesellschaft | Magnetic resonance imaging local coil composed of separate parts |
US8035384B2 (en) * | 2008-10-23 | 2011-10-11 | General Electric Company | Hybrid birdcage-TEM radio frequency (RF) coil for multinuclear MRI/MRS |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11061090B2 (en) | 2017-11-08 | 2021-07-13 | Canon Medical Systems Corporation | Magnetic resonance imaging apparatus and RF coil |
Also Published As
Publication number | Publication date |
---|---|
JP5248557B2 (en) | 2013-07-31 |
CN102401886A (en) | 2012-04-04 |
US20120025833A1 (en) | 2012-02-02 |
JP2012029734A (en) | 2012-02-16 |
CN102401886B (en) | 2016-03-30 |
US8749235B2 (en) | 2014-06-10 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US8749235B2 (en) | Birdcage coil for magnetic resonance imaging apparatus | |
EP2912483B1 (en) | Radio frequency birdcage coil with separately controlled ring members and rungs for use in a magnetic resonance imaging system | |
US8648678B2 (en) | Compact superconducting magnet device | |
US10168400B2 (en) | Magnetic resonance imaging apparatus including RF shield including slits | |
CN106908746B (en) | Head magnetic resonance imaging apparatus and head gradient coil assembly thereof | |
JP2015533327A (en) | Z-segmented radio frequency antenna apparatus for magnetic resonance imaging | |
US7432711B2 (en) | Radial coil arrangement for a magnetic resonance apparatus | |
CN110366688B (en) | Inductively feeding a coil for magnetic resonance imaging | |
US20150338482A1 (en) | Magnetic resonance imaging device and gradient coil | |
US11656305B2 (en) | MRI saddle based flexible array coil | |
JP5490460B2 (en) | Coil device, magnetic field generator, and magnetic resonance imaging device | |
US9880239B2 (en) | Radio frequency coil and magnetic resonance imaging apparatus | |
US10830846B2 (en) | Transmitting antenna for a magnetic resonance device | |
KR101890261B1 (en) | Magnetic resonance imaging birdcage coil assembly aligned along the z-axis | |
US11422214B2 (en) | Gradient coil system | |
JP2010508880A (en) | Split gradient coil for MRI | |
US7605588B2 (en) | RF coil assembly | |
US9620835B2 (en) | Decoupling of split ring resonators in magnetic resonance tomography | |
JP4664525B2 (en) | Coil for magnetic resonance imaging and magnetic resonance imaging apparatus | |
JP2019041795A (en) | High-frequency coil unit and magnetic resonance imaging device | |
US20180299519A1 (en) | Detector grid arrays for mr imaging | |
US10976389B2 (en) | Radiofrequency coil | |
CN216870782U (en) | Birdcage type radio frequency coil and magnetic resonance system | |
CN116973821A (en) | Radio frequency coil assembly | |
US20220349967A1 (en) | Arrayed structure and magnetic resonance imaging apparatus |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: GE HEALTHCARE JAPAN CORPORATION, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:IWAMA, MINA;ASABA, YUSUKE;ISHIGURO, TAKASHI;SIGNING DATES FROM 20110210 TO 20110214;REEL/FRAME:026674/0728 Owner name: GE MEDICAL SYSTEMS GLOBAL TECHNOLOGY COMPANY, LLC, Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GE HEALTHCARE JAPAN CORPORATION;REEL/FRAME:026674/0742 Effective date: 20110216 |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 4TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1551) Year of fee payment: 4 |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1552); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Year of fee payment: 8 |