IEEE Trans Ultrason Ferroelectr Freq Control. 2014 Mar;61(3):420-7. doi: 10.1109/TUFFC.2014.2927.
Ultrasound current source density imaging (UCSDI), which has application to the heart and brain, exploits the acoustoelectric (AE) effect and Ohm's law to detect and map an electrical current distribution. In this study, we describe 4-D UCSDI simulations of a dipole field for comparison and validation with bench-top experiments. The simulations consider the properties of the ultrasound pulse as it passes through a conductive medium, the electric field of the injected dipole, and the lead field of the detectors. In the simulation, the lead fields of detectors and electric field of the dipole were calculated by the finite element (FE) method, and the convolution and correlation in the computation of the detected AE voltage signal were accelerated using 3-D fast Fourier transforms. In the bench-top experiment, an electric dipole was produced in a bath of 0.9% NaCl solution containing two electrodes, which injected an ac pulse (200 Hz, 3 cycles) ranging from 0 to 140 mA. Stimulating and recording electrodes were placed in a custom electrode chamber made on a rapid prototype printer. Each electrode could be positioned anywhere on an x-y grid (5 mm spacing) and individually adjusted in the depth direction for precise control of the geometry of the current sources and detecting electrodes. A 1-MHz ultrasound beam was pulsed and focused through a plastic film to modulate the current distribution inside the saline-filled tank. AE signals were simultaneously detected at a sampling frequency of 15 MHz on multiple recording electrodes. A single recording electrode is sufficient to form volume images of the current flow and electric potentials. The AE potential is sensitive to the distance from the dipole, but is less sensitive to the angle between the detector and the dipole. Multi-channel UCSDI potentially improves 4-D mapping of bioelectric sources in the body at high spatial resolution, which is especially important for diagnosing and guiding treatment of cardiac and neurologic disorders, including arrhythmia and epilepsy.
超声电流密度成像（UCSDI）可应用于心脑领域，利用电声（AE）效应和欧姆定律来检测和绘制电流分布。本研究通过与台式实验进行比较和验证，描述了偶极子场的 4D-UCSDI 模拟。该模拟考虑了超声脉冲通过导电介质、注入偶极子的电场以及探测器的导联场的特性。在模拟中，使用有限元（FE）方法计算了探测器的导联场和偶极子的电场，并且通过 3D 快速傅里叶变换加速了检测到的 AE 电压信号的卷积和相关计算。在台式实验中，在含有两个电极的 0.9%NaCl 溶液浴中产生电偶极子，注入范围为 0 至 140mA 的交流脉冲（200Hz，3 个周期）。刺激和记录电极放置在快速原型打印机制作的定制电极室内。每个电极都可以放置在 x-y 网格（5mm 间距）上的任意位置，并可以单独调整深度方向，以精确控制电流源和检测电极的几何形状。1MHz 超声束脉冲聚焦通过塑料膜调制盐水中的电流分布。在多个记录电极上以 15MHz 的采样频率同时检测 AE 信号。单个记录电极足以形成电流流动和电位的体积图像。AE 电势对离偶极子的距离敏感，但对探测器和偶极子之间的角度不敏感。多通道 UCSDI 有可能以高空间分辨率改善体内生物电源的 4D 映射，这对于诊断和指导心律失常和癫痫等心脏和神经疾病的治疗尤其重要。
