Optimizing the efficiency of high-field multivoxel spectroscopic imaging by multiplexing in space and time
Optimizing the efficiency of high-field multivoxel spectroscopic imaging by multiplexing in space and time
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DOI：
10.1002/mrm.20942
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发表时间：
2006-07-01
影响因子：
3.3
通讯作者：
Gonen, Oded
中科院分区：
文献类型：
--
作者：
Goelman, Gadi;Liu, Songtao;Gonen, Oded
引入了一种新策略，可在 MR 光谱成像 (MRSI) 中从最大数量的体素中产生信息，每个体素在单位时间内具有最佳的信噪比 (SNR)。过去，最大采集占空比是通过在每个重复时间 (TR) 中及时复用多个单切片来获得的，而最佳 SNR 是通过对每个 TR 的整个感兴趣体积 (VOI) 进行编码来实现的。我们证明，通过在空间和时间上复用多个切片的多个板，可以同时实现最佳信噪比和采集效率。由于人脑 3D 质子 MRSI 中常见 VOI 的覆盖通常需要八个或更多切片，因此在 3 T 或更高磁场下，两个或更多切片可以适应最佳 TR（类似于 1.6 s）。由于通常四个或更少的切片将适合每个板，因此出于切片轮廓的原因，Hadamard 编码在该方向上受到青睐。事实证明，与当前的 3D 化学位移成像技术相比，在每个固定的检查长度下，新方法在 3 T 时给出的体素数量是相同的 SNR 和尺寸的两倍。结果表明，对于更广泛的空间覆盖或更高的场，该增益将会增加。
A new strategy to yield information from the maximum number of voxels, each at the optimum signal-to-noise ratio (SNR) per unit time, in MR spectroscopic imaging (MRSI) is introduced. In the past, maximum acquisition duty-cycle was obtained by multiplexing in time several single slices each repetition time (TR), while optimal SNR was achieved by encoding the entire volume of interest (VOI) each TR. We show that optimal SNR and acquisition efficiency can both be achieved simultaneously by multiplexing in space and time several slabs of several slices, each. Since coverage of common VOIs in 3D proton MRSI in the human brain typically requires eight or more slices, at 3 T or higher magnetic fields, two or more slabs can fit into the optimum TR (similar to 1.6 s). Since typically four or less slices would then fit into each slab, Hadamard encoding is favored in that direction for slice profile reasons. It is demonstrated that per fixed examination length, the new method gives, at 3 T, twice as many voxels, each of the same SNR and size, compared with current 3D chemical shift imaging techniques. It is shown that this gain will increase for more extensive spatial coverage or higher fields.