目的 提出用3个翻转角的多角度回波方法测量T1值时选取最佳翻转角的方法.方法 综合误差传递理论与破坏梯度回波脉冲序列的信号幅度计算公式,推导用于计算T1值的误差公式,当误差达到最小时的T1值所对应的翻转角即选定为最佳翻转角.通过在信号公式中加入随机噪声的方法进行计算机数值模拟,将最佳翻转角组合计算得出的T1的不确定性与其他翻转角组合得到的结果进行对比,验证用解析公式计算得到的T1值时,T1值的不确定性达到最小.将此方法应用于两个翻转角测量T1值的情况,检验该方法的正确性.结果 当翻转角达到最佳角度时,得到的T1值的不确定性最小.应用于两个翻转角情况时,得到的结果与文献中的结果完全一致.结论 应用本文提出的方法可获得T1值测量所用的最佳翻转角方法.%Objective To developing a method to determine the optimal flip angle using triple flip angle method for Tl measurement. Methods Using the theory of uncertainty propagation combined with the theoretical expression for spoiled gradient echo signal intensity at steady state, a theoretical expression for total uncertainties of Tl was derived. While the uncertainty of Tl achieved .minimal value, the flip angles were determined as the optimal flip angles. The computer simulation was carried out with random noise added to the signal intensity formula to verify the method, which was also confirmed for the two flip angles situation. The uncertainty of Tl from the optimal flip angles was compared with that from other flip angles. Results The computer simulation confirmed that the uncertainty of Tl achieved minimal when the flip angle was optimal. When the method was used for two flap angles, the results were consistent with references. Conclusion Using the proposed method, the optimal flip angles for Tl measurement can be got.
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