Utah Center for Advanced Imaging Research, Radiology Department, University of Utah, Salt Lake City, UT, USA.
Phys Med Biol. 2010 Oct 21;55(20):6157-74. doi: 10.1088/0031-9155/55/20/008. Epub 2010 Sep 29.
Several methods of flip angle mapping for magnetic resonance imaging have been proposed. We evaluated the accuracy of five methods of flip angle measurement in the presence of measurement noise. Our analysis was performed in a closed form by propagation of probability density functions (PDFs). The flip angle mapping methods compared were (1) the phase-sensitive method, (2) the dual-angle method using gradient recalled echoes (GRE), (3) an extended version of the GRE dual-angle method incorporating phase information, (4) the AFI method and (5) an extended version of the AFI method incorporating phase information. Our analysis took into account differences in required imaging time for these methods in the comparison of noise efficiency. PDFs of the flip angle estimate for each method for each value of true flip angle were calculated. These PDFs completely characterize the performance of each method. Mean bias and standard deviation were computed from these PDFs to more simply quantify the relative accuracy of each method over its range of measurable flip angles. We demonstrate that the phase-sensitive method provides the lowest mean bias and standard deviation of flip angle estimate of the five methods evaluated over a wide range of flip angles.
已经提出了几种用于磁共振成像的翻转角映射方法。我们评估了在存在测量噪声的情况下，五种翻转角测量方法的准确性。我们的分析通过概率密度函数（PDF）的传播以封闭形式进行。比较的翻转角映射方法是：(1) 相位敏感法，(2) 使用梯度回波（GRE）的双角度法，(3) 结合相位信息的扩展 GRE 双角度法，(4) AFI 方法，以及 (5) 结合相位信息的 AFI 方法的扩展版本。在比较噪声效率时，我们的分析考虑了这些方法所需的成像时间的差异。为每种方法的每个真实翻转角值计算了翻转角估计的 PDF。这些 PDF 完全描述了每种方法的性能。从这些 PDF 中计算出均值偏差和标准差，以更简单地量化每种方法在其可测量翻转角范围内的相对准确性。我们证明，在广泛的翻转角范围内，相位敏感法提供了五种评估方法中翻转角估计的最低均值偏差和标准差。
