Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan, Republic of China.
Phys Med Biol. 2010 Oct 7;55(19):5849-66. doi: 10.1088/0031-9155/55/19/015. Epub 2010 Sep 16.
The two-dimensional (2D) Nakagami image complements the ultrasound B-scan image when attempting to visualize the scatterer properties of tissues. The resolution of the Nakagami image is lower than that of the B-scan image, since the former is produced by processing the raw envelope data using a 2D sliding window with side lengths typically corresponding to three times the pulse length of the incident ultrasound. This paper proposes using three-dimensional (3D) Nakagami imaging for improving the resolution of the obtained Nakagami image and providing more complete information of scatterers for a better tissue characterization. The 3D Nakagami image is based on a voxel array composed of the Nakagami parameters constructed using a 3D sliding cube to process the 3D backscattered raw data. Experiments on phantoms with different scatterer concentrations were carried out to determine the optimal size of the sliding cube for a stable estimation of the Nakagami parameter. Tissue measurements on rat livers without and with fibrosis formation were further used to explore the practical feasibility of 3D Nakagami imaging. The results indicated that the side length of the cube used to construct the 3D Nakagami image must be at least two times the pulse length, which improved the resolution for each Nakagami image frame in the 3D Nakagami image. The results further demonstrated that the 3D Nakagami image is better than the conventional 2D Nakagami image for complementing the B-scan in detecting spatial variations in the scatterer concentration and classifying normal and fibrotic livers. This study suggests that 3D Nakagami imaging has the potential to become a new 3D quantitative imaging approach.
二维（2D）Nakagami 图像在尝试可视化组织散射特性时补充了超声 B 扫描图像。Nakagami 图像的分辨率低于 B 扫描图像，因为前者是通过使用边长通常对应于入射超声脉冲长度三倍的二维滑动窗口对原始包络数据进行处理而产生的。本文提出使用三维（3D）Nakagami 成像来提高获得的 Nakagami 图像的分辨率，并提供更完整的散射体信息，以更好地进行组织特征描述。3D Nakagami 图像基于由使用三维滑动立方体构建的 Nakagami 参数组成的体素阵列，用于处理三维反向散射原始数据。对具有不同散射体浓度的体模进行了实验，以确定滑动立方体的最佳尺寸，以稳定估计 Nakagami 参数。进一步对无纤维化和纤维化形成的大鼠肝脏进行组织测量，以探索 3D Nakagami 成像的实际可行性。结果表明，用于构建 3D Nakagami 图像的立方体边长必须至少是脉冲长度的两倍，这提高了 3D Nakagami 图像中每个 Nakagami 图像帧的分辨率。结果进一步表明，3D Nakagami 图像在补充 B 扫描以检测散射体浓度的空间变化和分类正常和纤维化肝脏方面优于传统的 2D Nakagami 图像。本研究表明，3D Nakagami 成像有可能成为一种新的 3D 定量成像方法。
