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4683432 Nuclear magnetic resonance methods and apparatus
III
New Patents
and second pole pieces, some of which shim coils are arranged with circular symmetry with regard to the exposed surface and some of which are arranged without circular symmetry.
coaxial cable with a lumped fixed capacitance connected in parallel thereacross and a conductive tuning rod positioned within the center of the coiled section so as to trim the parallel resonant frequency to the desired value.
4682112
4683431
NMR ANTENNA AND METHOD FOR DESIGNING THE SAME
MAGNETIC RESONANCE IMAGING OF HIGH VELOCITY FLOWS
Steve Beer assigned to Elscint Ltd An antenna system for nuclear magnetic resonance (NMR) imaging or spectroscopy devices which produce a uniform magnetic field in an object under examination includes transmit and receive antenna arrays each comprising a group of loop antennas. A signal generating circuit produces a set of input antenna signals which are applied to the loop antennas of the transmit array which transmits RF signals of a frequency that perturbs the magnetic moment of nuclei in a volume of the object. The receiving antenna array is responsive to NMR signals produced by the relaxation of perturbed nuclei in said volume for producing a set of output antenna that are applied to a signal processing circuit. A control circuit selectively controls the relative phases and amplitudes of at least one set of antenna signals to control the size and location of the region of the volume in which excitation of nuclei occurs, or from which NMR signals are processed. The relative phases and amplitudes can be controlled in such a way that nuclei in only a preselected region of the volume are excited, and that NMR signals from nuclei in only a preselected region of the volume are processed.
4682125 RF COIL COUPLING FOR MRI WITH TUNED RF REJECTION CIRCUIT USING COAX SHIELD CHOKE William H Harrison, Mitsuaki Arakawa, Barry McCarten assigned to The Regents of the University of California Undesirable RF coupling via the outside of an outer coaxial cable conductor to/from RF coils in a magnetic resonance imaging apparatus is minimized by employing a parallel resonance tuned RF choke in the circuit. The choke is realized by forming a short coiled section of the
Pradip M Pattany, Graham L Nayler assigned to Picker International Inc A main magnetic field coil and control cause a generally uniform main magnetic field through an image region. A resonance excitation control causes an R.F. coil to generate excitation pulses. An inversion pulse control causes the R.F. coil to generate a first 180 degree inversion pulse after the excitation pulse and a second 180 degree inversion pulse immediately preceding the excitation pulse. A slice gradient control and a read gradient control cause a gradient coil to generate complimentary slice selection gradients and complimentary read gradient profiles on either side of the first inversion pulse in such a manner that the effective first moment in time is substantially zero. By time shifting one or both of the slice selection and read gradients, resonating nuclei in the selected slice can be phase encoded. A transform algorithm transforms resonance signals received by the R.F. coil into image representations. A first memory receives real and imaginary components of the image representations when the read and slice selection gradients are not shifted and a second memory real and imaginary components of receives the image representations when one or both of the read and slice selection gradients are time shifted. From the arctangent of the real and imaginary components, first and second phase maps are calculated for storage in first and second phase memories. The intensity of each pixel of the phase maps varies with phase shift, hence velocity. By subtracting the two phase maps. correction is made for any stationary artifacts.
4683432 NUCLEAR MAGNETIC RESONANCE METHODS AND APPARATUS Ian Young, Sunbury on Thames, United Kingdom assigned to Picker International Inc
IV
New Patents
A nuclear magnetic resonance method and apparatus for examining a predetermined particular location (55) in a body wherein processed data obtained from four procedures are combined to extract processed data relating to the particular location. Each procedure comprises exciting spins in a region (45) of the body including the location (5.5) and acquiring and processing data in respect of the excited spins. In a first procedure the excited spins are of the same phase throughout the region (45). In a second procedure the excited spins are of a first phase in a first portion (49) of the region (45) of which portion the predetermined location (55) forms part, and are of the opposite phase in the rest of the region (45). In a third procedure the excited spins are of a first phase in a second portion (53) of the region which intersects the first portion (45) at the predetermined location (55) and are of the opposite phase in the rest of the region (45). In a fourth procedure the excited spins are of a first phase in the first and second portions (49 and 53) excluding the predetermined location (55), and are of the opposite phase in the rest of the region (45). Adding the processed data signals from the first and fourth procedures and subtracting the processed data signals for the second and third procedures gives a resultant signal relating to the predetermined location (55) only.
4683433 IMAGING METHOD AND APPARATUS USING NUCLEAR MAGNETIC RESONANCE Etsuji Yamamoto, Hideki Kohno, Masao Kuroda, Shigeru Matsui, Hidemi Shiono. Hachioji, Japan assigned to Hitachi Ltd An NMR imaging apparatus and method for detecting a nuclear spin resonance signal from an object, which is placed in a magnetic field, to produce images of the object. At an instant when the spins come into phase after the signal detection by a first spin excitation, RF magnetic field pulses are applied for rotating the direction of the spin to that opposite to the initial state. After that, the spin excitation and the signal direction of second time are conducted to measure the data which are different in the effect of the relaxation time from the first measurements. By repeating these sequences, it is possible to produce a plurality of images such as an intensity image or a relaxation time enhanced image.
4684889 NMR APPARATUS
COMPENSATED FOR PRIMARY FIELD CHANGES
Keiki Yamaguchi, Kazuya Hoshino, Hideto Iwaoka. Tokyo, Japan assigned to Yokogawa Hokushin Electric Corporation; Yokogawa Medical Systems Limite An object which can provide a reference for measuring the intensity of a primary magnetic held, is positioned in the vicinity of a subject being examined. A variation in the primary magnetic field intensity is detected, based on a frequency shift of data observed of the object, and is used to control the primary magnetic field intensity, or reference frequency for phase detection, or to correct image data. In this manner image quality is prevented from being degraded due to the variation of the primary magnetic field intensity.
4684890 PROCESS FOR THE GENERATION AND PROCESSING OF SIGNALS FOR OBTAINING BY NUCLEAR MAGNETIC RESONANCE A DISTORTIONFREE IMAGE FROM A HETEROGENEOUS POLARIZATION FIELD AndrefO Briguet, Mauriceice Goldman, Villeurbanne. France assigned to Commissariat a lf3 Energie Atomique Process for the generation and processing of signals for obtaining a nuclear magnetic resonance image, which is free from distortions. from an inhomogeneous polarization field Bf32 Bo+30 E+L (+I x.y,z+L ) using known 2D,FT and 3D,FT image coding methods involving the application of a 90 + 20 + 0 radiofrequency pulse in plane xOy, then a phase coding during time +96 +0 followed by frequency coding by applying, along Ox. a reading gradient during the acquisition of the free precession signal, which is then made to undergo Fourier transformations with respect to time and with respect to the gradient or gradients applied. + RE+ PA During a second series of sequences involving the successive application of the same gradients, the free precession system is subject to a second 180+20 +0 radiofrequency pulse at the start of establishing each reading gradient. + RE+ RE
New Patents
and second pole pieces, some of which shim coils are arranged with circular symmetry with regard to the exposed surface and some of which are arranged without circular symmetry.
coaxial cable with a lumped fixed capacitance connected in parallel thereacross and a conductive tuning rod positioned within the center of the coiled section so as to trim the parallel resonant frequency to the desired value.
4682112
4683431
NMR ANTENNA AND METHOD FOR DESIGNING THE SAME
MAGNETIC RESONANCE IMAGING OF HIGH VELOCITY FLOWS
Steve Beer assigned to Elscint Ltd An antenna system for nuclear magnetic resonance (NMR) imaging or spectroscopy devices which produce a uniform magnetic field in an object under examination includes transmit and receive antenna arrays each comprising a group of loop antennas. A signal generating circuit produces a set of input antenna signals which are applied to the loop antennas of the transmit array which transmits RF signals of a frequency that perturbs the magnetic moment of nuclei in a volume of the object. The receiving antenna array is responsive to NMR signals produced by the relaxation of perturbed nuclei in said volume for producing a set of output antenna that are applied to a signal processing circuit. A control circuit selectively controls the relative phases and amplitudes of at least one set of antenna signals to control the size and location of the region of the volume in which excitation of nuclei occurs, or from which NMR signals are processed. The relative phases and amplitudes can be controlled in such a way that nuclei in only a preselected region of the volume are excited, and that NMR signals from nuclei in only a preselected region of the volume are processed.
4682125 RF COIL COUPLING FOR MRI WITH TUNED RF REJECTION CIRCUIT USING COAX SHIELD CHOKE William H Harrison, Mitsuaki Arakawa, Barry McCarten assigned to The Regents of the University of California Undesirable RF coupling via the outside of an outer coaxial cable conductor to/from RF coils in a magnetic resonance imaging apparatus is minimized by employing a parallel resonance tuned RF choke in the circuit. The choke is realized by forming a short coiled section of the
Pradip M Pattany, Graham L Nayler assigned to Picker International Inc A main magnetic field coil and control cause a generally uniform main magnetic field through an image region. A resonance excitation control causes an R.F. coil to generate excitation pulses. An inversion pulse control causes the R.F. coil to generate a first 180 degree inversion pulse after the excitation pulse and a second 180 degree inversion pulse immediately preceding the excitation pulse. A slice gradient control and a read gradient control cause a gradient coil to generate complimentary slice selection gradients and complimentary read gradient profiles on either side of the first inversion pulse in such a manner that the effective first moment in time is substantially zero. By time shifting one or both of the slice selection and read gradients, resonating nuclei in the selected slice can be phase encoded. A transform algorithm transforms resonance signals received by the R.F. coil into image representations. A first memory receives real and imaginary components of the image representations when the read and slice selection gradients are not shifted and a second memory real and imaginary components of receives the image representations when one or both of the read and slice selection gradients are time shifted. From the arctangent of the real and imaginary components, first and second phase maps are calculated for storage in first and second phase memories. The intensity of each pixel of the phase maps varies with phase shift, hence velocity. By subtracting the two phase maps. correction is made for any stationary artifacts.
4683432 NUCLEAR MAGNETIC RESONANCE METHODS AND APPARATUS Ian Young, Sunbury on Thames, United Kingdom assigned to Picker International Inc
IV
New Patents
A nuclear magnetic resonance method and apparatus for examining a predetermined particular location (55) in a body wherein processed data obtained from four procedures are combined to extract processed data relating to the particular location. Each procedure comprises exciting spins in a region (45) of the body including the location (5.5) and acquiring and processing data in respect of the excited spins. In a first procedure the excited spins are of the same phase throughout the region (45). In a second procedure the excited spins are of a first phase in a first portion (49) of the region (45) of which portion the predetermined location (55) forms part, and are of the opposite phase in the rest of the region (45). In a third procedure the excited spins are of a first phase in a second portion (53) of the region which intersects the first portion (45) at the predetermined location (55) and are of the opposite phase in the rest of the region (45). In a fourth procedure the excited spins are of a first phase in the first and second portions (49 and 53) excluding the predetermined location (55), and are of the opposite phase in the rest of the region (45). Adding the processed data signals from the first and fourth procedures and subtracting the processed data signals for the second and third procedures gives a resultant signal relating to the predetermined location (55) only.
4683433 IMAGING METHOD AND APPARATUS USING NUCLEAR MAGNETIC RESONANCE Etsuji Yamamoto, Hideki Kohno, Masao Kuroda, Shigeru Matsui, Hidemi Shiono. Hachioji, Japan assigned to Hitachi Ltd An NMR imaging apparatus and method for detecting a nuclear spin resonance signal from an object, which is placed in a magnetic field, to produce images of the object. At an instant when the spins come into phase after the signal detection by a first spin excitation, RF magnetic field pulses are applied for rotating the direction of the spin to that opposite to the initial state. After that, the spin excitation and the signal direction of second time are conducted to measure the data which are different in the effect of the relaxation time from the first measurements. By repeating these sequences, it is possible to produce a plurality of images such as an intensity image or a relaxation time enhanced image.
4684889 NMR APPARATUS
COMPENSATED FOR PRIMARY FIELD CHANGES
Keiki Yamaguchi, Kazuya Hoshino, Hideto Iwaoka. Tokyo, Japan assigned to Yokogawa Hokushin Electric Corporation; Yokogawa Medical Systems Limite An object which can provide a reference for measuring the intensity of a primary magnetic held, is positioned in the vicinity of a subject being examined. A variation in the primary magnetic field intensity is detected, based on a frequency shift of data observed of the object, and is used to control the primary magnetic field intensity, or reference frequency for phase detection, or to correct image data. In this manner image quality is prevented from being degraded due to the variation of the primary magnetic field intensity.
4684890 PROCESS FOR THE GENERATION AND PROCESSING OF SIGNALS FOR OBTAINING BY NUCLEAR MAGNETIC RESONANCE A DISTORTIONFREE IMAGE FROM A HETEROGENEOUS POLARIZATION FIELD AndrefO Briguet, Mauriceice Goldman, Villeurbanne. France assigned to Commissariat a lf3 Energie Atomique Process for the generation and processing of signals for obtaining a nuclear magnetic resonance image, which is free from distortions. from an inhomogeneous polarization field Bf32 Bo+30 E+L (+I x.y,z+L ) using known 2D,FT and 3D,FT image coding methods involving the application of a 90 + 20 + 0 radiofrequency pulse in plane xOy, then a phase coding during time +96 +0 followed by frequency coding by applying, along Ox. a reading gradient during the acquisition of the free precession signal, which is then made to undergo Fourier transformations with respect to time and with respect to the gradient or gradients applied. + RE+ PA During a second series of sequences involving the successive application of the same gradients, the free precession system is subject to a second 180+20 +0 radiofrequency pulse at the start of establishing each reading gradient. + RE+ RE