Department of Radiology, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA.
Magn Reson Med. 2012 Nov;68(5):1376-82. doi: 10.1002/mrm.24132.
The purpose of this work was to evaluate a previously proposed approach that aims to improve the point spread function (PSF) of MR spectroscopic imaging (MRSI) to avoid corruption by lipid signal arising from neighboring voxels. Retrospective spatial filtering can be used to alter the PSF; however, this either reduces spatial resolution or requires extending the acquisition in k-space at the cost of increased imaging time. Alternatively, the method evaluated here, PSF-choice, can modify the PSF localization to reduce the contamination from adjacent lipids by conforming the signal response more closely to the desired MRSI voxel grid. This is done without increasing scan time or degrading SNR of important metabolites. PSF-choice achieves improvements in spatial localization through modifications to the radiofrequency excitation pulses. An implementation of this method is reported for MRSI of the prostate, where it is demonstrated that, in 13 of 16 pilot prostate MRSI scans, intravoxel spectral contamination from lipid was significantly reduced when using PSF-choice. Phantom studies were also performed that demonstrate, compared with MRSI with standard Fourier phase encoding, out-of-voxel signal contamination of spectra was significantly reduced in MRSI with PSF-choice.
这项工作的目的是评估一种先前提出的方法，旨在改善磁共振波谱成像 (MRSI) 的点扩散函数 (PSF)，以避免来自相邻体素的脂质信号的干扰。回顾性空间滤波可用于改变 PSF；然而，这要么降低空间分辨率，要么需要在 k 空间中扩展采集，以增加成像时间为代价。或者，这里评估的方法 PSF-choice 可以通过使信号响应更紧密地符合所需的 MRSI 体素网格来修改 PSF 定位，从而减少来自相邻脂质的污染。这不会增加扫描时间或降低重要代谢物的 SNR。PSF-choice 通过修改射频激励脉冲来实现空间定位的改进。本文报道了一种用于前列腺 MRSI 的该方法的实现，其中证明在 16 个试点前列腺 MRSI 扫描中的 13 个中，当使用 PSF-choice 时，来自脂质的体素内光谱干扰显著降低。还进行了体模研究，与具有标准傅里叶相位编码的 MRSI 相比，PSF-choice 下的 MRSI 中光谱的出体素信号污染显著降低。
