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Magnetic resonance ime - jingu modulo

机译:magnetic resonance IME - 筋骨modulo

摘要

In a magnetic resonance imaging system, object movement along an axis associated with readout magnetic gradient pulses is detected, quantized and compensated for in reconstructing an image slice. Phase- encoding magnetic gradient pulses in the sequence are arranged so that low-order phase-encoding pulses are distributed substantially uniformly during scanning time. In an N-slice acquisition, object movement is determined y arranging each of the N sets of phase-encoding gradient pulses comprising a multi-slice sequence such that at each scan time, at least one of the N sets contains a low-order phase-encoding gradient pulse. During data acquisition, echoes returned from low-order phase- encoding gradient pulses have sufficient signal-to-noise ratios to identify object position along the readout axis. Identification of object movement from one slice may be valid for other slices relatively adjacent physically in the object, so that all N slices are movement corrected during image reconstruction. Two-dimensional object position may also be identified and corrected by suitably exchanging the axes of N sets of pulses within a sequence. For a single slice acquisition, object position may be identified when scans associated with low-order phase-encoding gradient pulses are distributed evenly during imaging. After one- dimensional Fourier transformation, object position relative to a reference box function is determined using cross-correlation.
机译:在磁共振成像系统中,在重建图像切片时,沿与读出的磁梯度脉冲相关联的轴的对象运动被检测,量化和补偿。排列序列中的相位编码磁梯度脉冲,以使低阶相位编码脉冲在扫描时间内基本均匀地分布。在N切片采集中,通过排列N组包含多切片序列的相位编码梯度脉冲中的每组来确定对象移动,以便在每个扫描时间,N组中至少有一个包含低阶相位编码梯度脉冲。在数据采集期间,从低阶相位编码梯度脉冲返回的回波具有足够的信噪比,可以识别沿读出轴的物体位置。来自一个切片的对象运动的识别对于对象中物理上相对相邻的其他切片可能是有效的,因此在图像重建期间所有N个切片都被校正了运动。通过适当地交换序列中的N组脉冲的轴,还可以识别和校正二维物体位置。对于单个切片采集,当与低阶相位编码梯度脉冲相关联的扫描在成像过程中均匀分布时,可以识别对象位置。在进行一维傅立叶变换之后,使用互相关来确定相对于参考框函数的对象位置。

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