Schmidt Maria A, Fraser Karlene M
Department of Medical Physics, St George's Hospital, London, UK.
J Magn Reson Imaging. 2008 May;27(5):1122-9. doi: 10.1002/jmri.21310.
To propose an advanced phase-correction region-growing algorithm for two-point fat-water separation suitable for parotid assessment, and to evaluate the general performance of phase-correction algorithms.
Two region-growing algorithms were evaluated in test objects and in head images: the original phase-correction algorithm (OPC) and the advanced phase-correction algorithm with voxel size manipulation (VSM) which includes: 1) starting the region-growing process from images of lower resolution and subsequently stepping toward the original matrix size, and 2) limiting the use of low-pass filters to fat-water interfaces with partial volume effects
Fundamental problems relate to biological tissue spectrum being poorly approximated by two discrete peaks for fat and water. The VSM algorithm was shown to be less noise-sensitive, faster, and to produce a better approximation for the field inhomogeneity map. In head images (6 volunteers, 10 slices each) 43 errors were found with the OPC algorithm and only 6 errors with the VSM algorithm. Only the OPC algorithm produced errors surrounding the parotids (10 errors).
The VSM algorithm provides a more accurate and less noise-sensitive fat-water separation. This highly significant performance improvement allows the application of phase-correction algorithms to a wider range of clinical applications.
提出一种适用于腮腺评估的用于两点脂肪-水分离的先进相位校正区域生长算法，并评估相位校正算法的总体性能。
在测试对象和头部图像中评估了两种区域生长算法：原始相位校正算法（OPC）和具有体素大小操纵（VSM）的先进相位校正算法，其中VSM包括：1）从较低分辨率的图像开始区域生长过程，随后逐步达到原始矩阵大小，以及2）将低通滤波器的使用限制在具有部分容积效应的脂肪-水界面。
基本问题涉及脂肪和水的两个离散峰对生物组织光谱的近似效果较差。VSM算法显示出对噪声更不敏感、速度更快，并且能更好地近似场不均匀性图。在头部图像（6名志愿者，每人10层）中，OPC算法发现43个错误，而VSM算法仅发现6个错误。只有OPC算法在腮腺周围产生错误（10个错误）。
VSM算法提供了更准确且对噪声更不敏感的脂肪-水分离。这种显著的性能改进使得相位校正算法能够应用于更广泛的临床应用。
