Three-dimensional (3-D) ultrasound medical imaging provides advantages over a traditional 2-D visualization method. However, the use of a 2-D array to acquire 3-D images may result in a transducer composed of thousands of elements and a large amount of data in the front-end, making it impractical to implement high volume rate imaging and individually control all elements with the scanner. This paper proposes an original approach, valid for wideband operations centered on the design center frequency, to maintain a limited number of active elements and firing events, while preserving high resolution and volume rate. A 7 MHz 2-D array is composed of two circular concentric subparts. In the inner footprint the elements are distributed following a regular grid, while in the outer subpart a sparse non-grid solution is adopted. The inner circular dense array is composed of 256 elements with a pitch of 0.5λ. The overall footprint, delimited by the outer subpart, is equivalent to a 256-element array with a pitch of 1.5λ. All the elements of the inner subpart are activated in transmission. Following an optimization procedure, both subparts, including a subset of the elements placed in the inner footprint (i.e., sparse on-the-grid array) and the elements spread over the outer subpart (i.e., sparse off-the-grid array) are used to receive. A total number of 256 elements, defined by the sum of elements distributed in the inner and outer subparts, is fixed in reception. The proposed approach implies a multiline reception strategy, where for each transmission 3 × 3 firing events occur in reception. The sparse receive array is optimized by using a simulated annealing optimization. An original cost function is designed specifically to achieve successful results in wideband conditions. The receive array is optimized in order to obtain consistent results for different signal bandwidths of the excitation pulse. For all the desired bandwidths, the optimized array will provide the recovery of the lower lateral resolution of the transmission phase and, at the same time, a significant reduction of the undesired side lobe raised in the 3-D two-way beam pattern. The 3-D two-way beam pattern analysis reveals that the proposed solution is able to guarantee a lateral resolution of 1.35 mm at a focus depth of 25 mm for the three fractional signal bandwidths of interest (i.e., 30%, 50% and 70%) considered in the optimization process. The undesired side lobes are successfully suppressed especially when, as a consequence of the multiline strategy, non-coincident steering angles are used in transmission and reception. Moreover, thanks to the firing scheme adopted, a high-volume rate of 63 volumes per second may be achieved at the focus depth. The volume rate decreases to 32 volumes per second at twice the focal depth. Phantom image simulations show that the proposed method maintains a satisfactory and almost uniform image quality in terms of resolution and contrast for all the signal bandwidths of interest.

中文翻译：

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宽带 2-D 稀疏阵列优化结合多线接收用于实时 3-D 医学超声

三维 (3-D) 超声医学成像提供优于传统 2-D 可视化方法的优势。但是，使用二维阵列获取3维图像可能会导致换能器由数千个元件组成，前端数据量大，难以实现高容积率成像和单独控制。扫描仪的所有元素。本文提出了一种原始方法，适用于以设计中心频率为中心的宽带操作，以保持有限数量的有源元件和触发事件，同时保持高分辨率和音量速率。7 MHz 二维阵列由两个圆形同心子部分组成。在内部足迹中，元素按照规则网格分布，而在外部子部分中，采用稀疏非网格解决方案。内部圆形密集阵列由256个元素组成，间距为0.5λ。由外部子部分定界的整个足迹相当于一个 256 个元素的阵列，间距为 1.5λ。内部子部分的所有元素都在传输中被激活。遵循优化程序，两个子部分，包括放置在内部足迹中的元素子集（即，稀疏的网格阵列）和分布在外部子部分（即，稀疏的网格外阵列）上的元素用来接收。总共 256 个元素，由分布在内部和外部子部分的元素的总和定义，在接收中是固定的。所提出的方法暗示了一种多线接收策略，其中每次传输都会在接收中发生 3 × 3 触发事件。通过使用模拟退火优化来优化稀疏接收阵列。原始成本函数专门设计用于在宽带条件下获得成功的结果。接收阵列经过优化，以便在激励脉冲的不同信号带宽下获得一致的结果。对于所有所需的带宽，优化的阵列将提供传输相位较低横向分辨率的恢复，同时显着减少在 3-D 双向波束模式中升高的不需要的旁瓣。3-D 双向光束模式分析表明，对于三个感兴趣的分数信号带宽（即 30%、50% 和 70 %) 在优化过程中考虑。不需要的旁瓣被成功抑制，尤其是当，作为多线策略的结果，在传输和接收中使用非重合转向角。此外，由于采用了发射方案，在焦深处可以实现每秒 63 卷的高容量率。在两倍焦深处，体积速率降低到每秒 32 个体积。幻影图像模拟表明，所提出的方法在所有感兴趣的信号带宽的分辨率和对比度方面保持了令人满意且几乎一致的图像质量。