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Electric Current Mapping using the Acousto-Electric Effect

机译：使用声电效应的电流映射

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Conventional methods for mapping cardiac current fields lack either spatial resolution (e.g. ECG) or are time consuming (e.g., intra-cardiac catheter electrode mapping). We present a method based on the acousto-electric effect (AEE) with potential for rapid mapping of current fields in the heart with high spatial resolution. The AEE is a pressure-induced conductivity modulation, in which focused ultrasound can be used as a spatially localized pressure source. When an ultrasound beam is focused between a pair of recording electrodes in a homogeneous conductive medium, an induced voltage will be produced due to the pressure-modulated conductivity and local current density. The amplitude of the voltage change should be proportional to fluctuations in current density, such as those generated during the cardiac cycle, in the region of focused ultrasound. Preliminary experiments demonstrate the feasibility of this method. A 540 kHz ultrasound transducer is focused between two tin electrodes lying parallel to the beam axis. These electrodes inject current into a 0.9% saline solution. A pair of insulated stainless steel electrodes exposed at the tip is used to record voltage. To simulate a cardiac current, a low frequency current waveform is injected into the sample such that the peak current density (8 mA/cm~2) approximates cardiac currents. The transducer is pulsed at different delays after waveform initiation. Delays are chosen such that the low frequency waveform is adequately sampled. Using this approach an emulated ECG waveform has been successfully reconstructed from the ultrasound modulated voltage traces.
机译：用于映射心电图的常规方法缺少空间分辨率（例如ECG）或耗时（例如，心脏导管电极映射）。我们提出了一种基于声学电气效应（AEE）的方法，其具有高空间分辨率的心脏中当前场的快速映射。 AEE是一种压力诱导的电导率调制，其中聚焦超声可以用作空间局部的压力源。当超声波光束聚焦在均匀导电介质中的一对记录电极之间时，由于压力调制的电导率和局部电流密度，将产生感应电压。电压变化的幅度应与电流密度的波动成比例，例如在聚焦超声区域中的心循环中产生的电流的波动。初步实验证明了这种方法的可行性。 540 kHz超声换能器聚焦在与梁轴平行的两个锡电极之间。这些电极将电流注入0.9％的盐水溶液中。在尖端暴露的一对绝缘不锈钢电极用于记录电压。为了模拟心电电流，将低频电流波形注入样品，使得峰值电流密度（8mA / cm〜2）近似于心电流。在波形启动后，换能器在不同的延迟下脉冲。选择延迟使得低频波形是充分采样的。使用此方法已从超声调制电压迹线成功重建模拟的ECG波形。

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