NMR spectroscopy and imaging coil
First Claim
1. A magnetic resonance imaging apparatus comprising:
- a means for creating a primary magnetic field through an examination region;
a gradient field means for selectively causing magnetic field gradients across the primary magnetic field;
a first radio frequency means for supplying radio frequency resonance excitation and manipulation signals of a first frequency;
a second radio frequency means for supplying radio frequency resonance excitation and manipulation signals of a second frequency;
a radio frequency coil which is concurrently tuned to both the first and second frequencies for selectively exciting magnetic resonance of nuclei in the examination region which are excited to resonance at the first and second frequencies;
a first coupling means for selectively coupling the first radio frequency means with the radio frequency coil;
a second coupling means for selectively coupling the second radio frequency means with the radio frequency coil;
a reconstruction means for reconstructing magnetic resonance signals emanating from the examination region into an electronic representation of nuclei which resonate at the first frequency and into an electronic representation of nuclei which resonate at the second frequency;
a first memory means for selectively storing representations of the nuclei which resonate at the first frequency;
a second memory means for storing the representations of nuclei that resonate at the second frequency; and
,means for displaying the first and second frequency representations.
1 Assignment
0 Petitions
Accused Products
Abstract
In a magnetic resonance imaging apparatus, a first frequency radio signal source (20a) is connected in quadrature with a four fold symmetric birdcage coil (24) at 90° spaced connection points (80a,b). A source of a second radio frequency signal is directly connected with the birdcage coil by first and second inductive couplings (70a,b). The birdcage coil includes tank circuits (52) and capacitors (58, 60) in the end connectors. The capacitance of the end connectors is simultaneously adjustable by a tuning ring (62) to adjust a first resonance frequency of the coil and the capacitance of the tank circuits is selectively adjustable to adjust a second resonant frequency of the birdcage coil. In this manner, the birdcage coil is simultaneously tuned to two frequencies and can operate in quadrature at either one. PIN diodes (92) are provided for de-tuning the coil such that it operates in a third mode in which no resonance frequency exists such that the birdcage coil does not interfere with reception of resonance signals by a surface coil (42). When operating in quadrature, additional PIN diodes (114) are provided for connecting the RF feed point to one node (102a) of a 90° phase shift circuit (100) in the transmit mode and to the opposite node (102b) of the 90° phase shift circuit in the receive mode.
69 Citations
22 Claims
-
1. A magnetic resonance imaging apparatus comprising:
-
a means for creating a primary magnetic field through an examination region; a gradient field means for selectively causing magnetic field gradients across the primary magnetic field; a first radio frequency means for supplying radio frequency resonance excitation and manipulation signals of a first frequency; a second radio frequency means for supplying radio frequency resonance excitation and manipulation signals of a second frequency; a radio frequency coil which is concurrently tuned to both the first and second frequencies for selectively exciting magnetic resonance of nuclei in the examination region which are excited to resonance at the first and second frequencies; a first coupling means for selectively coupling the first radio frequency means with the radio frequency coil; a second coupling means for selectively coupling the second radio frequency means with the radio frequency coil; a reconstruction means for reconstructing magnetic resonance signals emanating from the examination region into an electronic representation of nuclei which resonate at the first frequency and into an electronic representation of nuclei which resonate at the second frequency; a first memory means for selectively storing representations of the nuclei which resonate at the first frequency; a second memory means for storing the representations of nuclei that resonate at the second frequency; and
,means for displaying the first and second frequency representations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
-
-
18. In a magnetic resonance imaging apparatus in which radio frequency signals are transmitted into an examination region from a birdcage coil tuned to two frequencies, each corresponding to a resonance frequency of a different nuclei in which resonance is to be excited, one of the nuclei requiring higher power than the other, the improvement comprising:
the birdcage coil operating in a high pass mode at the resonance frequency of the frequency requiring higher power and in a low pass mode for the other frequency.
-
19. In a magnetic resonance scanner in which radio frequency signals of first and second frequencies are provided to a birdcage coil which is concurrently tuned to the first and second frequencies for transmitting the first and second radio frequency energy into an examination region, the improvement comprising:
a direct coupling means for coupling the radio frequency signals of the first frequency to the birdcage coil and an inductive coupling means for coupling the radio frequency signals of the second frequency to the birdcage coil.
-
20. In a magnetic resonance imager in which radio frequency energy with first and second frequencies from a radio frequency transmitter means is supplied through first and second coupling means to a birdcage coil concurrently tuned to the first and second frequencies for transmitting radio frequency energy of the first and second frequencies into an examination region, the improvement comprising:
a first tank circuit incorporated into the first coupling means for preventing coupling of the first coupling means with the birdcage coil at the second frequency and a second tank circuit incorporated in the second coupling means for preventing the second coupling means from coupling with the birdcage coil at the first frequency, whereby each coupling means is prevented from interfering with the operation of the birdcage coil and from disturbing the symmetry of the birdcage coil when the birdcage coil is operating at the other frequency.
-
21. In a magnetic resonance imaging apparatus in which a dual mode birdcage radio frequency coil transmits radio frequency signals into an examination region, the improvement comprising:
operating the birdcage coil in quadrature at both the first and second frequency.
-
22. In a magnetic resonance imaging apparatus in which a birdcage coil is tuned to first and second frequencies for selectively transmitting radio frequency energy into an examination region at either of the first and second frequencies, the improvement comprising:
during a receive portion of a magnetic resonance imaging cycle, the birdcage coil being selectively tunable to any one of (1) the first frequency, (2) the second frequency, and (3) a third mode in which no resonant frequency exists such that the birdcage coil is decoupled from both frequencies, whereby the birdcage coil does not interfere with resonance signals detected by other coils.
Specification