Magnetic resonance system and method for rephasing spin systems in slices in slice multiplexing measurement sequences for magnetic resonance imaging
First Claim
1. A method configured for generating magnetic resonance (MR) images with slice multiplexing, comprising:
- with a control computer, operating an MR data acquisition unit in order to generate a basic magnetic field having a basic field direction, and in order to radiate a first radio-frequency pulse that deflects a first nuclear spin system in a first slice of a subject, thereby giving said first spin system in said first slice a magnetization in a plane that is transverse to said basic field direction in which said magnetization has a phase that exhibits a phase evolution represented as a first coherence curve;
with said control computer, operating said MR data acquisition unit in order to radiate a second radio-frequency pulse that deflects a second spin system in a second slice of the subject, thereby giving said second spin system in said second slice a magnetization in another plane that is transverse to said basic field direction in which said magnetization has a phase that exhibits a phase evolution represented as a second coherence curve;
with said control computer, controlling operation of said MR data acquisition unit in order to cause a beginning of a second radio-frequency pulse to be time-shifted by a difference time period, with respect to a beginning of said first radio-frequency pulse, that is shorter than a duration of said first radio-frequency pulse;
with said control computer, operating said MR data acquisition unit in order to impress a correction phase on at least one of said first and second spin systems and in order to thereafter detect, in a given signal detection time period, a first signal representing said magnetization of said first nuclear spin system resulting from said deflection of said first nuclear spin system and in order to detect a second MR signal representing said magnetization of said second spin system resulting from said deflection of said second nuclear spin system;
with said control computer, operating said MR data acquisition unit in order to impress said correction phase, whereby each of said first and second coherence curves is rephased thereby causing detection of said first and second MR signals simultaneously in said given signal detection time period; and
from said control computer, making the detected first and second MR signals available in electronic form as a data file.
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Abstract
In a method for rephasing a first spin system in a first slice with a first coherence curve and a second spin system of a second slice with a second coherence curve, in the generation of MR images with slice multiplexing, a first RF pulse deflects the spin system of the first slice and a second RF pulse deflects the spin system of the second slice. The beginning of the second RF pulse is time-shifted with respect to the beginning of the first RF pulse by a time period that is shorter than the duration of the first RF pulse. A rephasing correction impresses a correction phase on at least one of the spin systems, and signals of the spin systems are respectively detected. The coherence curves are rephased so detection of the signals occurs simultaneously.
23 Citations
16 Claims
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1. A method configured for generating magnetic resonance (MR) images with slice multiplexing, comprising:
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with a control computer, operating an MR data acquisition unit in order to generate a basic magnetic field having a basic field direction, and in order to radiate a first radio-frequency pulse that deflects a first nuclear spin system in a first slice of a subject, thereby giving said first spin system in said first slice a magnetization in a plane that is transverse to said basic field direction in which said magnetization has a phase that exhibits a phase evolution represented as a first coherence curve; with said control computer, operating said MR data acquisition unit in order to radiate a second radio-frequency pulse that deflects a second spin system in a second slice of the subject, thereby giving said second spin system in said second slice a magnetization in another plane that is transverse to said basic field direction in which said magnetization has a phase that exhibits a phase evolution represented as a second coherence curve; with said control computer, controlling operation of said MR data acquisition unit in order to cause a beginning of a second radio-frequency pulse to be time-shifted by a difference time period, with respect to a beginning of said first radio-frequency pulse, that is shorter than a duration of said first radio-frequency pulse; with said control computer, operating said MR data acquisition unit in order to impress a correction phase on at least one of said first and second spin systems and in order to thereafter detect, in a given signal detection time period, a first signal representing said magnetization of said first nuclear spin system resulting from said deflection of said first nuclear spin system and in order to detect a second MR signal representing said magnetization of said second spin system resulting from said deflection of said second nuclear spin system; with said control computer, operating said MR data acquisition unit in order to impress said correction phase, whereby each of said first and second coherence curves is rephased thereby causing detection of said first and second MR signals simultaneously in said given signal detection time period; and from said control computer, making the detected first and second MR signals available in electronic form as a data file. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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2. A method as claimed in claim one comprising:
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with said control computer, setting said difference time period, according to a to at least one of (1) total duration of radiating said first and second radio-frequency pulses and implementing said correction phase and said signal detection time period, (2) an amplitude of said first and second radio-frequency pulses, and (3) a signal strength of said radio-frequency pulses; and with said control computer, selecting said correction phase dependent on at least one of said difference time period, said first coherence curve and said second coherence curve.
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16. A magnetic resonance imaging system configured for generating magnetic resonance (MR) images with slice multiplexing, comprising:
an MR data acquisition unit comprising a basic field magnet and a radio-frequency radiator; a control computer configured to operate said MR data acquisition unit in order to cause said basic field magnet to generate a basic magnetic field having a basic field direction, and in order to radiate a first radio-frequency pulse from said radio-frequency radiator that deflects a first nuclear spin system in a first slice of a subject, thereby giving said first spin system in said first slice a magnetization in a plane that is transverse to said basic field direction in which said magnetization has a phase that exhibits a phase evolution represented as a first coherence curve; said control computer being configured to operate said MR data acquisition unit in order to radiate a second radio-frequency pulse from said radio-frequency radiator that deflects a second spin system in a second slice of the subject, thereby giving said second spin system in said second slice a magnetization in another plane that is transverse to said basic field direction in which said magnetization has a phase that exhibits a phase evolution represented as a second coherence curve; said control computer being configured to control operation of said MR data acquisition unit in order to cause a beginning of said second radio-frequency pulse to be time-shifted by a difference time period, with respect to a beginning of said first radio-frequency pulse, that is shorter than a duration of said first radio-frequency pulse; said control computer being configured to operate said MR data acquisition unit in order to impress a correction phase on at least one of said first and second spin systems, and in order to thereafter detect, in a given signal detection time period, a first signal representing said magnetization of said first nuclear spin system resulting from said deflection of said first nuclear spin system and to deflect a second MR signal representing said magnetization of said second spin system resulting from said deflection of said second nuclear spin system; said control computer being configured to impress said correction phase in order to cause each of said first and second coherence curves to be rephased whereby detection of said first and second MR signals occurs simultaneously in said given signal detection time period; and said control computer being configured to make the detected first and second MR signals available from said control computer in electronic form as a data file.
Specification