Magnetic resonance imaging device with multiple RF coils applying half-pulse waveforms for selective excitation of a local region
First Claim
1. A magnetic resonance imaging apparatus configured for imaging a selected portion of a subject placed in a static magnetic field, said magnetic resonance imaging apparatus comprising RF transmitting means for applying an RF excitation pulse to said subject an RF irradiation control means for controlling irradiation phase of the RF excitation pulse, RF receiving means for detecting nuclear magnetic resonance signals generated from the subject, a control means for controlling the RF transmitting means, the RF irradiation control means and the RF receiving means, and an image formation means for reconstructing an image of said selected portion of the subject by using the nuclear magnetic resonance signals,said RF transmitting means including a first coil and one or more additional coils,wherein the RF irradiation control means controls RF irradiation so that the RF excitation pulse is simultaneously applied to each of said first RF excitation coil and said one or more additional RF excitation coils such that within a single simultaneously applied RF excitation, a phase of a second half of a waveform of an RF excitation output of at least one of said first coil and said one or more additional RF excitation coils, after the temporal center of the simultaneously applied RF excitation pulse, is maintained to be held different by 180°
- from a phase of the first half of the pulse waveform, of the RF excitation output, such that the RF excitation is selectively applied only to a local region of the selected portion of the subject.
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Accused Products
Abstract
An MRI apparatus suitable for realizing selective excitation utilizing multiple RF transmitting coils (parallel transmission) is provided. This MRI apparatus is provided with, as an RF receiving coil or RF transmitting coil, an RF transmitting coil 104 comprising a loop coil 210, primary differential coil 220 and secondary differential coil 230 having a common central axis 201. Upon imaging, the coils 210, 220 and 230 constituting the RF transmitting coil 104 are simultaneously driven by RF signals with the same phase, and only the differential coils 220 and 230 are driven in the second half of irradiation time with phases different by 180° from the phases for the first half. Alternatively, two times of measurements are performed as a pair, in which, in the first measurement, the coils 210, 220 and 230 are simultaneously driven with RF signals of the same phase, then in the second measurement, only the differential coils 220 and 230 are driven with phases inverse to the phases for the first measurement, and the signals measured respectively are added. Such imaging or addition of the results of two times of the measurement provides a profile for exciting a local region. This enables selective excitation of only a desired region without using any RF pulse for signal suppression.
26 Citations
17 Claims
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1. A magnetic resonance imaging apparatus configured for imaging a selected portion of a subject placed in a static magnetic field, said magnetic resonance imaging apparatus comprising RF transmitting means for applying an RF excitation pulse to said subject an RF irradiation control means for controlling irradiation phase of the RF excitation pulse, RF receiving means for detecting nuclear magnetic resonance signals generated from the subject, a control means for controlling the RF transmitting means, the RF irradiation control means and the RF receiving means, and an image formation means for reconstructing an image of said selected portion of the subject by using the nuclear magnetic resonance signals,
said RF transmitting means including a first coil and one or more additional coils, wherein the RF irradiation control means controls RF irradiation so that the RF excitation pulse is simultaneously applied to each of said first RF excitation coil and said one or more additional RF excitation coils such that within a single simultaneously applied RF excitation, a phase of a second half of a waveform of an RF excitation output of at least one of said first coil and said one or more additional RF excitation coils, after the temporal center of the simultaneously applied RF excitation pulse, is maintained to be held different by 180° - from a phase of the first half of the pulse waveform, of the RF excitation output, such that the RF excitation is selectively applied only to a local region of the selected portion of the subject.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A magnetic resonance imaging apparatus configured for imaging a selected portion of a subject placed in a static magnetic, field, said magnetic resonance imaging apparatus comprising:
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an RF transmission section configured to apply an RF excitation pulse through a RF excitation first coil and one or more additional RF excitation coils to said subject; receiving means configured to detect nuclear magnetic resonance signals generated from the subject, a control section configured to control an irradiation phase of the RF excitation pulse and control the RF transmission section and the RF receiving means, and a signal processing section configured to reconstruct an image of said selected portion of the subject by using the nuclear magnetic resonance signals, wherein the control section controls RF irradiation so that the RF excitation pulse is simultaneously applied to each of said RF excitation first coil and said one or more additional RF excitation coils, such that within a single simultaneously applied RF excitation, a phase of a second half of a waveform of an RF excitation output of at least one of said RF excitation first coil and said one or more additional RF excitation coils, after the temporal center of the simultaneously applied RF excitation pulse, is maintained to be held different by 180°
from a phase of the first half of the RF excitation output waveform, such that RF excitation is selectively applied only to a local region of the selected portion of the subject.
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Specification