Olafsson Ragnar, Witte Russell S, Huang Sheng-Wen, O'Donnell Matthew
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
IEEE Trans Biomed Eng. 2008 Jul;55(7):1840-8. doi: 10.1109/TBME.2008.919115.
Surgery to correct severe heart arrhythmias usually requires detailed maps of the cardiac activation wave prior to ablation. The pinpoint electrical mapping procedure is laborious and limited by its spatial resolution (5-10 mm). We propose ultrasound current source density imaging (UCSDI), a direct 3-D imaging technique that potentially facilitates existing mapping procedures with superior spatial resolution. The technique is based on a pressure-induced change in resistivity known as the acoustoelectric (AE) effect, which is spatially confined to the ultrasound focus. AE-modulated voltage recordings are used to map and reconstruct current densities. In this preliminary study, we tested UCSDI under controlled conditions and compared it with conventional electrical mapping techniques. A 2-D dipole field was produced by a pair of electrodes in a bath of 0.9% NaCl solution. Boundary electrodes detected the AE signal while a 7.5-MHz focused ultrasound transducer was scanned across the bath. UCSDI located the current source and sink to within 1 mm of their actual positions. A future UCSDI system potentially provides real-time 3-D images of the cardiac activation wave coregistered with anatomical ultrasound and would greatly facilitate corrective procedures for heart abnormalities.
纠正严重心律失常的手术通常需要在消融前获取心脏激活波的详细图谱。精确的电标测程序既费力又受空间分辨率（5 - 10毫米）的限制。我们提出了超声电流源密度成像（UCSDI），这是一种直接的三维成像技术，有可能以更高的空间分辨率促进现有的标测程序。该技术基于压力引起的电阻率变化，即声电（AE）效应，其在空间上局限于超声焦点。利用声电调制的电压记录来绘制和重建电流密度。在这项初步研究中，我们在受控条件下测试了UCSDI，并将其与传统电标测技术进行了比较。在0.9%氯化钠溶液浴中，通过一对电极产生二维偶极场。边界电极检测声电信号，同时一个7.5兆赫的聚焦超声换能器在溶液浴上进行扫描。UCSDI将电流源和电流汇定位在其实际位置的1毫米范围内。未来的UCSDI系统有可能提供与解剖超声配准的心脏激活波的实时三维图像，并将极大地促进心脏异常的矫正手术。
