Achieving sufficient spectral bandwidth for volumetric 1H echo-planar spectroscopic imaging at 4 Tesla
Achieving sufficient spectral bandwidth for volumetric 1H echo-planar spectroscopic imaging at 4 Tesla
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DOI：
10.1002/mrm.20593
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发表时间：
2005-09-01
影响因子：
3.3
通讯作者：
Schuff, N
中科院分区：
文献类型：
--
作者：
Ebel, A;Maudsley, AA;Schuff, N
完全覆盖体内质子代谢物光谱，包括下场共振，需要大约9ppm的光谱带宽。活体回波平面光谱成像(EPSI)的频谱带宽主要受振荡读出梯度的梯度强度、梯度转换速率和对人体周围神经刺激的限制。此外，传统的EPSI重建分别使用偶数和奇数读出回波，仅使用一半的频谱带宽。为了在EPSI中恢复全频谱带宽，以前曾建议应用隔行扫描傅里叶变换(IFT)，它同时使用偶数和奇数回波。然而，这种方法对于活体3D EPSI的有效性还没有得到彻底的分析。在本笔记中，讨论了IFT方法的局限性，并提出了一种替代方法，循环光谱展开，该方法基于典型体内光谱模式的先验知识。
Complete coverage of the in vivo proton metabolite spectrum, including downfield resonances, requires a spectral bandwidth of approximately 9 ppm. Spectral bandwidth of in vivo echoplanar spectroscopic imaging (EPSI) is primarily limited by gradient strength of the oscillating readout gradient, gradient slew rate, and limits on peripheral nerve stimulation for human subjects. Furthermore, conventional EPSI reconstruction, which utilizes even and odd readout echoes separately, makes use of only half the spectral bandwidth. In order to regain full spectral bandwidth in EPSI, it has previously been suggested to apply an interlaced Fourier transform (iFT), which uses even and odd echoes simultaneously. However, this method has not been thoroughly analyzed regarding its usefulness for in vivo 3D EPSI. In this Note, limitations of the iFT method are discussed and an alternative, cyclic spectral unwrapping, is proposed, which is based on prior knowledge of typical in vivo spectral patterns.