Method and apparatus for acquiring free-breathing MR images using navigator echo with saturation RF pulse
First Claim
Patent Images
1. An magnetic resonance (MR) imaging apparatus comprising:
- a plurality of gradient coils positioned about a bore of a magnet to impress a polarizing magnetic field and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly to acquire MR images; and
a computer programmed to apply a pulse sequence during an imaging period of a free-breathing gated acquisition, the pulse sequence defined by;
a navigator RF excitation pulse designed to selectively excite a tracker column;
an image acquisition segment designed to acquire MR data from a region-of-interest; and
a navigator RF saturation pulse designed to saturate the tracker column such that longitudinal-magnetization recovery in the tracker column is uniform for a next imaging period.
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Abstract
A system and method of free-breathing MR imaging saturates an entire navigator profile at the end of an imaging segment of physiological motion cycle, e.g., heart cycle, thereby providing a uniform recovery of longitudinal magnetization for the next imaging cycle. Through use of at least one dephaser gradient following the image acquisition segment and a navigator RF saturation pulse, residual transverse magnetization is dephased and spins within a navigator tracker are saturated to ensure a uniform recovery of longitudinal magnetization for the next imaging period.
37 Citations
25 Claims
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1. An magnetic resonance (MR) imaging apparatus comprising:
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a plurality of gradient coils positioned about a bore of a magnet to impress a polarizing magnetic field and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly to acquire MR images; and a computer programmed to apply a pulse sequence during an imaging period of a free-breathing gated acquisition, the pulse sequence defined by; a navigator RF excitation pulse designed to selectively excite a tracker column; an image acquisition segment designed to acquire MR data from a region-of-interest; and a navigator RF saturation pulse designed to saturate the tracker column such that longitudinal-magnetization recovery in the tracker column is uniform for a next imaging period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of MR imaging comprising the steps of:
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(A) acquiring navigator echo data elicited by an RF navigator excitation pulse applied to a tracker portion of a subject to be imaged; (B) applying an imaging sequence to acquire MR data from a region-of-interest; (C) applying an RF saturation pulse to saturate spins within the tracker portion after acquisition of the MR data; (D) repeating steps (A)-(C) in each cycle of a physiologically gated acquisition; and (E) reconstructing an image based on the acquired MR data. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A computer readable storage medium having instructions stored thereon that when executed by a computer cause the computer to:
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acquire navigator tracking data from a navigator excitation region; acquire imaging data for a segment of k-space from a region-of-interest; suppress residual longitudinal magnetization in the navigator excitation region; repeat the acquisition of tracking data and imaging data and suppression of longitudinal magnetization every cycle of a gated acquisition until k-space is acquired; and reconstruct an image based on the imaging data. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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Specification