Institute of Medical Engineering, Ruhr-University Bochum, Bochum, Germany.
Phys Med Biol. 2013 Sep 7;58(17):6163-78. doi: 10.1088/0031-9155/58/17/6163. Epub 2013 Aug 16.
In diagnostic ultrasound imaging, the image reconstruction quality is crucial for reliable diagnosis. Applying reconstruction algorithms based on the acoustic wave equation, the obtained image quality depends significantly on the physical material parameters accounted for in the equation. In this contribution, we extend a proposed iterative nonlinear one-parameter compressibility reconstruction algorithm by the additional reconstruction of the object's inhomogeneous mass density distribution. The improved iterative algorithm is able to reconstruct inhomogeneous maps of the object's compressibility and mass density simultaneously using only one conventional linear transducer array at a fixed location for wave transmission and detection. The derived approach is based on an acoustic wave equation including spatial compressibility and mass density variations, and utilizes the Kaczmarz method for iterative material parameter reconstruction. We validate our algorithm numerically for an unidirectional pulse-echo breast imaging application, and thus generate simulated measurements acquired from a numerical breast phantom with realistic compressibility and mass density values. Applying these measurements, we demonstrate with two reconstruction experiments the necessity to calculate the mass density in case of tissues with significant mass density inhomogeneities. When reconstructing spatial mass density variations, artefacts in the breast's compressibility image are reduced resulting in improved spatial resolution. Furthermore, the compressibility relative error magnitude within a diagnostically significant region of interest (ROI) decreases from 3.04% to 2.62%. Moreover, a second image showing the breast's inhomogeneous mass density distribution is given to provide additional diagnostic information. In the compressibility image, a spatial resolution moderately higher than the classical half-wavelength limit is observed.
在诊断超声成像中，图像重建质量对于可靠的诊断至关重要。应用基于波动方程的重建算法，所获得的图像质量在很大程度上取决于方程中考虑的物理材料参数。在本研究中，我们通过额外重建物体的非均匀质量密度分布，扩展了一种已提出的迭代非线性单参数可压缩性重建算法。改进的迭代算法能够使用仅一个固定位置的常规线性换能器阵列同时重建物体的可压缩性和质量密度的非均匀图谱，用于波的传输和检测。所提出的方法基于包含空间可压缩性和质量密度变化的波动方程，并利用 Kaczmarz 方法进行迭代材料参数重建。我们针对单向脉冲回波乳腺成像应用进行了数值验证，从而生成了使用具有实际可压缩性和质量密度值的数值乳腺体模采集的模拟测量结果。应用这些测量结果，我们通过两个重建实验证明了在存在显著质量密度非均匀性的组织中计算质量密度的必要性。当重建空间质量密度变化时，乳腺可压缩性图像中的伪影减少，从而提高了空间分辨率。此外，感兴趣区域（ROI）内的可压缩性相对误差幅度从 3.04%降低至 2.62%。此外，还给出了第二张显示乳房不均匀质量密度分布的图像，以提供附加的诊断信息。在可压缩性图像中，观察到比经典半波长极限稍高的空间分辨率。
