Pulse-echo sound speed estimation based on a Nakagami model of the echo amplitude
Pulse-echo sound speed estimation based on a Nakagami model of the echo amplitude
复制标题
基于回波幅度 Nakagami 模型的脉冲回波声速估计
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
J. Zagzebski
中科院分区：
文献类型：
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作者：
I. Rosado;T. Hall;J. Zagzebski
这项工作探索了使用反向散射回波信号幅度的 Nakagami 模型作为图像清晰度的间接评估来估计软组织声速 ct。该方法利用了 Nakagami 模型形状参数 m 与分辨率单元内散射体数量之间的关系。参数 m 用于跟踪随着商用超声系统中波束形成器声速 cbf 的变化，超声系统点扩散函数大小的变化。 m 的估计性能与图像清晰度的直接测量（即回波强度相关单元的大小 Sc）进行比较。所提出的方法在对应于脂肪和非脂肪软组织的两个组织模拟体模上进行了测试。使用低频和高频线性阵列换能器扫描模型。将换能器固定在每个体模的扫描窗口上，采集同一体模平面的 19 个射频数据帧，其中 cbf 关于预期 ct 对称变化。首先优化估计 Sc 的回波数据量。然后根据不同 cbf 的回波数据估计 m 和 Sc。选择 m 和 Sc 最小化时的 cbf 值作为 ct 估计值。 CT 估计的统计数据是通过扫描独立的模型平面获得的。结果表明，当 cbf 接近 ct 时，m 和 Sc 都最小化。高频传感器的 CT 估计偏差小于低频传感器的偏差。随着Sc的增加，Nakagami参数m逐渐增加到m=1的值。这是达到瑞利散射极限的结果。 Nakagami 参数因其估计简单性而颇具吸引力。
This work explores the use of the Nakagami model of the backscattered echo signal amplitude as an indirect assessment of image sharpness to estimate soft tissue sound speed ct. This method exploits the relationship between the Nakagami model shape parameter m and the number of scatterers within the resolution cell. The parameter m is used to track changes in the size of the ultrasound system's point spread function as the beamformer sound speed in a commercial ultrasound system, cbf, is varied. The estimation performance of m is compared to a direct measure of image sharpness, i.e., the size Sc of the echo intensity correlation cell. The proposed method is tested on two tissue mimicking phantoms corresponding to fatty and non-fatty soft tissues. The phantoms were scanned with low- and high-frequency linear array transducers. Keeping the transducers fixed on the scanning window of each phantom, 19 radiofrequency data frames of the same phantom plane were acquired with cbf varying symmetrically about the expected ct, The amount of echo data to estimate Sc was first optimized. Then both m and Sc were estimated from echo data with different cbf. The cbf values at which m and Sc were minimized were chosen as ct estimates. Statistics of ct estimates were obtained by scanning independent phantom planes. Results show that both m and Sc are minimized when cbf is close to ct. Bias of ct estimates from the high-frequency transducer was smaller than the bias from the low frequency transducer. The Nakagami parameter m gradually increased up to a value of m=1 as Sc increased. This results from reaching the Rayleigh scattering limit. The Nakagami parameter is attractive due to its estimation simplicity.