Department of Medical Imaging and Radiological Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan, ROC.
Ultrason Imaging. 2012 Apr;34(2):110-24. doi: 10.1177/016173461203400204.
The Nakagami image is a complementary imaging mode for pulse-echo ultrasound B-scan to characterize tissues. White noise in anechoic areas induces artifacts in the Nakagami image. Recently, we proposed a noise-assisted correlation algorithm (NCA) for suppressing the Nakagami artifact. In the NCA, artificial white noise is intentionally added twice to backscattered signals to produce two noisy data, which are used to establish a correlation profile for rejecting noise. This study explored the effects of artificial noise level on the NCA to suppress the artifact of the Nakagami image. Simulations were conducted to produce B-mode images of anechoic regions under signal-to-noise ratios (SNRs) of 20, 10 and 5 dB. Various artificial noise levels ranging from 0.1- to 1-fold of the intrinsic noise amplitude were used in the NCA for constructing the Nakagami images. Phantom experiments were conducted to validate the performance of using the optimal artificial noise level suggested by the simulation results to suppress the Nakagami artifacts by the NCA. The simulation results indicated that the artifacts of the Nakagami image in the anechoic regions can be gradually suppressed by increasing the artificial noise level used in the NCA to improve the image contrast-to-noise ratio (CNR). The CNR of the Nakagami image reached 20 dB when the artificial noise level was 0.7-fold of the intrinsic noise amplitude. This criterion was demonstrated by the phantom results to provide the NCA with an excellent ability to obtain artifact-free Nakagami images.
Nakagami 图像是一种用于脉冲回波超声 B 扫描以对组织进行特征描述的互补成像模式。在无声区域的白噪声会在 Nakagami 图像中产生伪影。最近，我们提出了一种噪声辅助相关算法（NCA）来抑制 Nakagami 伪影。在 NCA 中，人为地向背散射信号添加两次白噪声以产生两个噪声数据，然后使用这些数据建立相关轮廓以抑制噪声。本研究探讨了人为噪声水平对 NCA 抑制 Nakagami 图像伪影的影响。通过模拟产生了 SNR 为 20、10 和 5 dB 的无声区域的 B 模式图像。在 NCA 中，使用了从固有噪声幅度的 0.1 倍到 1 倍的各种人为噪声水平来构建 Nakagami 图像。进行了体模实验以验证使用模拟结果建议的最佳人为噪声水平通过 NCA 抑制 Nakagami 伪影的性能。模拟结果表明，通过增加 NCA 中使用的人为噪声水平，可以逐渐抑制无声区域 Nakagami 图像的伪影，从而提高图像的对比噪声比（CNR）。当人为噪声水平为固有噪声幅度的 0.7 倍时，Nakagami 图像的 CNR 达到 20 dB。该标准通过体模结果得到验证，表明 NCA 具有出色的能力，可以获得无伪影的 Nakagami 图像。
