Reducing voxel bleed in hadamard-encoded MRI and MRS
Reducing voxel bleed in hadamard-encoded MRI and MRS
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DOI：
10.1002/mrm.20903
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发表时间：
2006-06-01
影响因子：
3.3
通讯作者：
Gonen, Oded
中科院分区：
文献类型：
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作者：
Goelman, Gadi;Liu, Songtao;Gonen, Oded
Hadamard编码的点扩展函数（PSF）由于实际（与内在相反）原因而偏离其理想轮廓。有限的射频（RF）脉冲长度和梯度强度导致切片轮廓缺陷，导致串扰（“体素出血”）高达17%，带宽为1 KHz，射频脉冲为5.12 ms，低于3 mT/m。这可能会对定位和定量产生不利影响，从而影响临床实用性。阿达玛RF脉冲合成，利用其独特的能力来编码非连续切片的一个简单的修改提出并示出显着提高PSF。计算机模拟，体外和体内实验证实了体素出血减少的理论推导，从类似的17%到低于5%，每个阿达玛编码的方向。
The point spread function (PSF) of Hadamard encoding deviates from its ideal profile due to practical (as opposed to intrinsic) reasons. Finite radiofrequency (RF) pulse length and gradient strength cause slice profile imperfections that lead to cross-talk ("voxel bleed") as large as 17% for a 1-KHz bandwidth, 5.12-ms RF pulse under 3 mT/m. This could adversely affect localization and quantification, and consequently clinical usefulness. A simple modification of the Hadamard RF pulse synthesis that exploits its unique ability to encode noncontiguous slices is proposed and shown to markedly improve the PSF. Computer simulation, in vitro and in vivo experiments confirm the theoretical derivation of voxel bleed reduction from similar to 17% to below 5% per Hadamard-encoded direction.