Simultaneous magnetic resonance imaging of multiple human organs

• US 5,374,890 A
• Filed: 03/17/1993
• Issued: 12/20/1994
• Est. Priority Date: 07/24/1992
• Status: Expired due to Term

• Current Assignee: Picker International, Inc. (Koninklijke Philips N.V.)
• Original Assignee: Picker International, Inc. (Koninklijke Philips N.V.)
• Inventors: Patrick, John L., McNally, James M., Zou, Xueming
• Primary Examiner(s): ARANA, LOUIS M
• Application Number:
  US08/032,128
• Time in Patent Office: 643 Days
• Field of Search: 324/307, 324/309, 324/314, 324/318, 324/322, 128/653.3
• US Class Current: 324/318
• CPC Class Codes: G01R 33/3415 comprising arrays of sub-coils , i.e. phased-array coils with flexible receiver channels
• CPC Class Codes: G01R 33/385 using gradient magnetic field coils
• CPC Class Codes: G01R 33/422 of the radio frequency field
• CPC Class Codes: G01R 33/54 Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console

Abstract

Superconducting magnets (10) of a magnetic resonance imager create static magnetic fields through an examination region (12). Gradient magnetic field coils (30) under control of a gradient magnetic field control (42) generate gradient magnetic fields across the examination region (12), as a whole. A plurality of surface coils (36, 38) receive radio frequency signals from each of two distinct subregions within the examination region (12). The two receiver coils are connected with separate receivers (60₁, 60₂) which demodulate the received magnetic resonance signals. The magnetic resonance signals are reconstructed (76) into an image representation (80, 82) of the first and second subregions. In the embodiment of FIGS. 1 and 2, a radio frequency transmitter (40) and a whole body coil (32) generate and manipulate the magnetic resonance signals within the first and second subregions. In the embodiment of FIGS. 3 and 4, a plurality of transmitters (40₁, 40₂, . . . ) convey RF signals to the surface coils such that the surface coils operate in both a transmit and receive mode. Regardless whether a single transmitter or a series of transmitters is utilized, a sequence control (44) controls the transmitter(s) and the gradient control (42) to conduct conventional magnetic resonance imaging sequences in coordination in both subregions.

Claims

1. A magnetic resonance imaging system which simultaneously images at least first and second displaced organs of a subject, the system comprising:

a main magnet means for generating a static magnetic field through an examination region in which a portion of the subject including the first and second organs is disposed;

a gradient field means for selectively generating magnetic field gradients across the examination region as a whole;

a magnetic resonance excitation means for exciting magnetic resonance in at least first and second organs of the subject portion in the examination region;

a magnetic resonance imaging sequence control means connected with the resonance excitation means and the gradient field means for causing the resonance excitation means and the gradient means to apply RF and gradient field pulses of magnetic resonance imaging sequences to the examination region;

a first radio frequency coil disposed adjacent the first organ for receiving magnetic resonance signals from the first organ;

a second radio frequency coil displaced from the first radio frequency coil and disposed adjacent the second organ for receiving magnetic resonance signals from the second organ;

a first radio frequency receiver means connected with the first radio frequency coil for receiving and demodulating magnetic resonance signals received by the first radio frequency coil;

a second radio frequency receiver means for receiving and demodulating magnetic resonance signals received by the second radio frequency coil;

a reconstruction means for reconstructing magnetic resonance signals received and demodulated by the first radio frequency receiver means into first electronic image representations of the first organ and for reconstructing magnetic resonance signals received and demodulated by the second radio frequency receiver means into second electronic image representations of the second organ;

a video processing means for selectively converting the first and second electronic image representations into a human-readable display.

2. The system as set forth in claim 1 wherein the first radio frequency coil is a quadrature coil and further including a quadrature combiner connected between the first radio frequency coil and the first radio frequency receiver means, the first combiner means imposing a 90°

relative phase shift on one of two components received from the first radio frequency coil and combining the two components together.

3. The system as set forth in claim 2 wherein the first radio frequency coil includes a birdcage coil.

4. The system as set forth in claim 2 wherein the second radio frequency coil is a quadrature coil and further including a quadrature combiner connected between the second radio frequency coil and the second radio frequency receiver means, the second combiner means imposing a 90°

relative phase shift on one of two components received from the second radio frequency coil and combining the two components together.

5. The magnetic resonance imaging system which simultaneously images at least separate first and second regions of a subject, the system comprising:

a main magnet means for generating a static magnetic field through the separate first and second regions of a subject;

a gradient field means for selectively generating magnetic field gradients across the separate first and second regions;

a whole body RF coil disposed around the examination region;

a radio frequency transmitter for transmitting radio magnetic pulses to the whole body RF coil for exciting magnetic resonance in the separate first and second regions;

a magnetic resonance imaging sequence control means connected with the radio frequency transmitter and the gradient field means for causing the gradient means to apply RF and gradient field pulses of magnetic resonance imaging sequences to the separate first and second regions;

first and second non-overlapping radio magnetic coils disposed adjacent the first and second regions, respectively, for receiving magnetic resonance signals from the first and second regions, respectively, the first and second radio magnetic coils being physically separated from each other;

a first radio frequency receiver means connected with the first radio frequency coil for receiving and demodulating magnetic resonance signals received by the first radio frequency coil;

a second radio frequency receiver means for receiving and demodulating magnetic resonance signals received by the second radio frequency coil;

a reconstruction means for reconstructing magnetic resonance signals received and demodulated by the first radio frequency receiver means into first electronic image representations and for reconstructing magnetic resonance signals received and demodulated by the second radio frequency receiver means into second electronic image representations;

a video processing means for selectively converting the first and second electronic image representations into a human-readable display.

6. The system as set forth in claim 5 wherein the whole body RF coil is a quadrature coil and further including a quadrature divider connected between the transmitter and the whole body RF coil for dividing the radio frequency pulses into two components and shifting one of the components 90°

relative to the other.

7. The system as set forth in claim 6 wherein the first radio frequency coil is a quadrature coil and further including a first quadrature combiner means connected between the first radio frequency coil and the first radio frequency receiver means, the first quadrature combiner means imposing a 90°

relative phase shift on one of two components received from the first radio frequency coil and combining the two components together.

8. The system as set forth in claim 7 wherein the second radio frequency coil is a quadrature coil and further including a second quadrature combiner means connected between the second radio frequency coil and the second radio frequency receiver means, the second quadrature combiner means imposing a 90°

relative phase shift to one of two components received from the second radio frequency coil and combining the two components together.

9. The system as set forth in claim 6 wherein at least the first radio frequency coil is a quadrature coil and wherein the first radio frequency receiver means includes a first digital receiver connected with a first port of the first radio frequency coil for receiving one quadrature component therefrom and a second digital receiver connected with a second port of the first radio frequency coil for receiving a second quadrature component therefrom.

10. A magnetic resonance imaging system which simultaneously images at least two regions of a subject, the system comprising:

a main magnetic means for generating a static magnetic field through a portion of a subject in an examination region;

a gradient field means for selectively generating magnetic field gradients across the examination region as a whole;

a magnetic resonance excitation means for exciting magnetic resonance in at least first and second subregions of the subject portion in the examination region;

a magnetic resonance imaging sequence control means connected with the resonance excitation means and the gradient field means for causing the resonance excitation means and the gradient means to apply RF and gradient field pulses of magnetic resonance imaging sequences to the examination region;

a first radio frequency quadrature coil having first and second output ports the first radio frequency quadrature coil being disposed adjacent the first subregion for receiving magnetic resonance signals from the first subregion;

a second radio frequency quadrature coil having first and second output ports disposed adjacent the second subregion for receiving magnetic resonance signals from the second subregion;

a first digital receiver connected with the first radio frequency quadrature coil first port for receiving and demodulating one quadrature component therefrom;

a second digital receiver connected with the first radio frequency quadrature coil second port for receiving and demodulating a second quadrature component therefrom;

a third digital receiver connected with the second radio frequency quadrature coil first port for receiving and demodulating a quadrature component therefrom;

a fourth digital receiver connected with the second radio frequency quadrature coil second port for receiving and demodulating a quadrature component therefrom;

a reconstruction means for reconstructing magnetic resonance signals received and demodulated by the first, second, third, and fourth digital receivers into at least first and electronic image representations;

a video processing means for selectively converting the first and second electronic image representations into a human-readable display.

11. A magnetic resonance imaging system which simultaneously images at least first and second separated regions of a subject, the system comprising:

a main magnet means for generating a static magnetic field through the first and second separated regions of a subject;

a gradient field means for selectively generating magnetic field gradients across the first and second regions;

a first radio frequency coil disposed adjacent the first region for transmitting radio frequency excitation signals into and receiving radio frequency magnetic resonance signals from the first region;

a second radio frequency coil disposed adjacent the second region for transmitting radio frequency excitation signals into and receiving radio frequency magnetic resonance signals from the second region;

a first radio frequency transmitter means connected with the first radio frequency coils;

a second radio frequency transmitter means connected with the second radio frequency coil, such that the first and second radio frequency coils operate in both transmit and reception modes;

a magnetic resonance imaging sequence control means connected with the first and second radio frequency transmitter means and the gradient field means for causing the first and second radio frequency transmitter means and the gradient means to apply RF and gradient field pulses of magnetic resonance imaging sequences to the first and second separated regions;

a first radio frequency receiver means connected with the first radio frequency coil for receiving and demodulating magnetic resonance signals received by the first radio frequency coil;

a second radio frequency receiver means for receiving and demodulating magnetic resonance signals received by the second radio frequency coil;

a reconstruction means for reconstructing magnetic resonance signals received and demodulated by the first radio frequency receiver means into first electronic image representations and for reconstructing magnetic resonance signals received and demodulated by the second radio frequency receiver means into second electronic image representations;

a video processing means for selectively converting the first and second electronic image representations into a human-readable display.

12. The system as set forth in claim 11 wherein the first radio frequency coil includes a quadrature coil and further including a first combiner/divider means connected between the first radio frequency coil and the first radio frequency transmitter means and the first radio frequency receiver means, the first combiner/divider means in a transmit mode divides an RF signal received from the first radio frequency transmitter means into two transmit mode components and shifts the relative phase of one of the transmit mode components by 90°

relative to the other, the two transmit mode components being conveyed to the first radio frequency coil and, in a receiving mode, the first combiner/divider means imposes a 90°

phase shift on one received resonance signal component received from the first receiver coil relative to a second received resonance signal component and combines the two received resonance signal components, the combined resonance signal components being conveyed to the first receiver means.

13. The system as set forth in claim 12 wherein the second radio frequency coil includes a quadrature coil and further including a second combiner/divider means connected between the second radio frequency coil and the second radio frequency transmitter means and the second radio frequency receiver means, the second combiner/divider means in a transmit mode divides an RF signal received from the second radio frequency transmitter means into two transmit mode components and shifts the relative phase of one of the transmit mode components by 90°

, the two transmit mode components being conveyed to the second receiver coil and, in a receiving mode, the second combiner/divider means imposes a 90°

phase shift on one received resonance signal component received from the second radio frequency coil relative to a second received resonance signal component and combines the two received resonance signal components, the combined resonance signal components being conveyed to the second radio frequency receiver means.

14. The system as set forth in claim 13 wherein the first and second transmitter means include digital transmitters and the first and second receiver means include digital receivers.

15. The system as set forth in claim 12 wherein the first coil includes a birdcage coil.

16. The system as set forth in claim 11 wherein at least the first radio frequency coil includes a quadrature coil having first and second ports and wherein the first radio frequency receiver means includes a first digital receiver connected with the first port for receiving one quadrature component therefrom and a second digital receiver connected with the second port for receiving a second quadrature component therefrom.

17. A magnetic resonance imaging apparatus comprising:

a static magnetic field means for creating a common static magnetic field through an examination region in which at least first and second displaced portions of a subject are disposed;

a magnetic field gradient means for applying magnetic field gradients across the examination region as a whole;

a magnetic resonance means for exciting and manipulating magnetic resonance concurrently in at least the first and second displaced portions of the subject;

at least first and second displaced, non-overlapping RF coils disposed adjacent the first and second displaced portions, respectively, for concurrently receiving magnetic resonance signals from the first and second displaced portions, respectively, at least one of the first and second RF coils being a quadrature coil;

a processing means for processing the magnetic resonance signals received by the first and second RF coils into first and second image representations, respectively.

18. A method of magnetic resonance imaging comprising:

creating a static magnetic field through an examination region in which at least a portion of a subject is disposed;

applying magnetic field gradients across the examination region as a whole while exciting and manipulating magnetic resonance concurrently in at least first and second selected displaced subregions of the subject;

concurrently receiving magnetic resonance signals from the first and second displaced subregions with non-overlapping first and second RF coils disposed adjacent the first and second displaced subregions, respectively;

concurrently demodulating the resonance signals received by the first and second RF coils with first and second receivers, respectively;

processing the demodulated magnetic resonance signals from the first and second receivers into first and second image representations, respectively.

19. The method as set forth in claim 18 wherein the step of exciting and manipulating magnetic resonance includes applying radio frequency signals to the first and second RF coils, such that the first and second RF coils work in both transmit and receive modes.

20. The method as set forth in claim 18 wherein the step of exciting and manipulating magnetic resonance includes applying RF signals to a common RF coil which radiates RF signals into both the first and second regions.

21. The method as set forth in claim 18 wherein the excitation and reception of magnetic resonance signals in at least the first subregion is in quadrature.