MR IMAGING WITH B1 MAPPING
First Claim
1. Method of MR imaging of at least a portion of a body, the method comprising the steps of:
- subjecting the portion of the body to an imaging sequence of RF pulses and switched magnetic field gradients, which imaging sequence is a stimulated echo sequence including;
i) at least two preparation RF pulses radiated toward the portion of the body during a preparation period,ii) an off-resonant Bloch-Siegert RF pulse radiated toward the portion of the body during the preparation period within a time interval between the at least two preparation RF pulses, andiii) one or more refocusing RF pulses radiated toward the portion of the body during an acquisition period temporally subsequent to the preparation period;
acquiring one or more stimulated echo MR signals during the acquisition period;
deriving a B1 map indicating the spatial distribution of the RF field of the RF pulses within the portion of the body from the acquired stimulated echo MR signals.
1 Assignment
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Accused Products
Abstract
The invention relates to a method of MR imaging, wherein a portion of a body is subjected to an imaging sequence of RF pulses and switched magnetic field gradients, which imaging sequence is a stimulated echo sequence including an off-resonant Bloch-Siegert RF pulse (BS) radiated during a preparation period (21) of the stimulated echo sequence. A B1 map is derived from the acquired stimulated echo MR signals. Moreover, the invention relates to a method of MR imaging, wherein a portion of a body is subjected to a first imaging sequence, which comprises a first composite excitation RF pulse consisting of two RF pulse components having essentially equal flip angles and being out of phase by essentially 90°. Further, the portion of the body is subjected to a second imaging sequence, wherein a B1 map is derived from signal data acquired by means of the first and second imaging sequences.
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Citations
17 Claims
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1. Method of MR imaging of at least a portion of a body, the method comprising the steps of:
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subjecting the portion of the body to an imaging sequence of RF pulses and switched magnetic field gradients, which imaging sequence is a stimulated echo sequence including; i) at least two preparation RF pulses radiated toward the portion of the body during a preparation period, ii) an off-resonant Bloch-Siegert RF pulse radiated toward the portion of the body during the preparation period within a time interval between the at least two preparation RF pulses, and iii) one or more refocusing RF pulses radiated toward the portion of the body during an acquisition period temporally subsequent to the preparation period; acquiring one or more stimulated echo MR signals during the acquisition period; deriving a B1 map indicating the spatial distribution of the RF field of the RF pulses within the portion of the body from the acquired stimulated echo MR signals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Method of MR imaging of at least a portion of a body, the method comprising the steps of:
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subjecting the portion of the body to a first imaging sequence, which comprises a first composite excitation RF pulse consisting of two RF pulse components having essentially equal flip angles and being out of phase by essentially 90°
;acquiring first MR signal data; subjecting the portion of the body to a second imaging sequence; acquiring second MR signal data; deriving a B1 map indicating the spatial distribution of the RF field of the RF pulses within the portion of the body from the first and second signal data. - View Dependent Claims (9, 10, 11, 12, 13)
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14. MR device comprising at least one main magnet coil for generating a uniform, steady magnetic field within an examination volume, a number of gradient coils for generating switched magnetic field gradients in different spatial directions within the examination volume, at least one RF coil for generating RF pulses within the examination volume and/or for receiving MR signals from a body of a patient positioned in the examination volume, a control unit for controlling the temporal succession of RF pulses and switched magnetic field gradients, a reconstruction unit, and a visualization unit, wherein the MR device is arranged to perform the following steps:
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subjecting the portion of the body to an imaging sequence of RF pulses and switched magnetic field gradients, which imaging sequence is a stimulated echo sequence including; i) at least two preparation RF pulses radiated toward the portion of the body (10) during a preparation period, ii) an off-resonant Bloch-Siegert RF pulse radiated toward the portion of the body (10) during the preparation period within a time interval between the at least two preparation RF pulses, and iii) one or more refocusing RF pulses radiated toward the portion of the body (10) during an acquisition period temporally subsequent to the preparation period; acquiring one or more stimulated echo MR signals during the acquisition period; deriving a B1 map indicating the spatial distribution of the RF field of the RF pulses within the portion of the body (10) from the acquired stimulated echo MR signals.
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15. MR device comprising at least one main magnet coil for generating a uniform, steady magnetic field within an examination volume, a number of gradient coils for generating switched magnetic field gradients in different spatial directions within the examination volume, at least one RF coil for generating RF pulses within the examination volume and/or for receiving MR signals from a body of a patient positioned in the examination volume, a control unit for controlling the temporal succession of RF pulses and switched magnetic field gradients, a reconstruction unit, and a visualization unit, wherein the MR device is arranged to perform the following steps:
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subjecting the portion of the body to a first imaging sequence, which comprises a first composite excitation RF pulse consisting of two RF pulse components having essentially equal flip angles and being out of phase by essentially 90°
;acquiring first MR signal data; subjecting the portion of the body to a second imaging sequence; acquiring second MR signal data; deriving a B1 map indicating the spatial distribution of the RF field of the RF pulses within the portion of the body from the first and second signal data.
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16. Computer program to be run on a MR device, which computer program comprises instructions for:
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generating an imaging sequence of RF pulses and switched magnetic field gradients, which imaging sequence is a stimulated echo sequence including; i) at least two preparation RF pulses radiated toward the portion of the body (during a preparation period, ii) an off-resonant Bloch-Siegert RF pulse radiated toward the portion of the body during the preparation period within a time interval between the at least two preparation RF pulses, and iii) one or more refocusing RF pulses radiated toward the portion of the body during an acquisition period temporally subsequent to the preparation period; acquiring one or more stimulated echo MR signals during the acquisition period; deriving a B1 map indicating the spatial distribution of the RF field of the RF pulses within the portion of the body from the acquired stimulated echo MR signals.
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17. Computer program to be run on a MR device, which computer program comprises instructions for:
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generating a first imaging sequence, which comprises a first composite excitation RF pulse consisting of two RF pulse components having essentially equal flip angles and being out of phase by essentially 90°
;acquiring first MR signal data; generating a second imaging sequence; acquiring second MR signal data; deriving a B1 map indicating the spatial distribution of the RF field of the RF pulses within the portion of the body from the first and second signal data.
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Specification