Capturing Signals from Fast-relaxing Spins with Frequency-Swept MRI: SWIFT
Capturing Signals from Fast-relaxing Spins with Frequency-Swept MRI: SWIFT
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DOI：
10.1002/9780470034590.emrstm1259
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发表时间：
2012-01-01
期刊：
影响因子：
--
通讯作者：
Nixdorf, Donald R.
中科院分区：
文献类型：
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作者：
Garwood, Michael;Idiyatullin, Djaudat;Nixdorf, Donald R.
傅立叶变换扫描成像，SWIFT，是一种相对较新的超短T-2敏感MRI序列。它通过利用核磁共振早期的连续波实验的特征，颠覆了最近脉冲核磁共振方法的范例。通过以径向方式收集对象的投影来产生图像。每个投影都是在存在场梯度的情况下通过频率扫描来激发的。MR信号以分时方式在扫频脉冲的间隙中采集。信号在时间和空间上按顺序被激发，导致相位变化。通过将接收的数据与脉冲波形相关来消除由扫频激励引起的相位变化。其结果相当于使用短硬脉冲的FID激励。对于高带宽SWIFT，捕获前信号的相位演化时间低至几微秒，因此保留了来自极短T(2)S自旋(数十微秒)的信号。在这里，我们描述了SWIFT序列和信号处理程序，以及一些应用，包括人脑的磁化准备成像，骨和软骨的体外成像，体外牙齿成像，以及体外大鼠脑的高分辨率相位成像。
Sweep imaging with Fourier transformation, SWIFT, is a relatively new addition to the class of ultra-short T-2-sensitive MRI sequences. It reverses the recent paradigm of pulsed NMR methodology by exploiting features of continuous-wave experiments from the early days of NMR. Images are produced by collecting projections of the object in a radial manner. Each projection is excited by a frequency sweep in the presence of a field gradient. MR signal is acquired in gaps in the frequency-swept pulse, in a time-shared manner. Signals are excited sequentially in time and space, leading to phase variation. Phase variation due to the frequency-swept excitation is removed by correlation of the received data with the pulse waveform. The result is equivalent to FID excitation using a short hard pulse. The phase evolution time of signal prior to acquisition is as low as a few microseconds for high bandwidth SWIFT, so signals from spins with extremely short T(2)s (tens of microseconds) are preserved. Here we describe the SWIFT sequence and signal processing procedures, along with some applications, including magnetization-prepared imaging of the human brain, in vitro imaging of bone and cartilage, in vitro dental imaging, and high-resolution phase imaging of in vitro rat brain.