Title :
Mapping cardiac currents using Ultrasound Current Source Density Imaging
Author :
Olafsson, R. ; Jia, C. ; Huang, S.-W. ; Kim, K. ; Witte, R.S. ; O´Donnell, M.
Author_Institution :
Dept. of Biomed. Eng., Univ. of Michigan, Ann Arbor, MI
Abstract :
We describe the first mapping of biological current in a live heart using ultrasound current source density imaging (UCSDI). Ablation procedures that treat severe heart arrhythmias require detailed maps of the cardiac activation wave. UCSDI can potentially improve on existing mapping procedures which are time-consuming and limited by its poor spatial resolution (5-10 mm). UCSDI is based on a pressure-induced change in resistivity known as the acousto-electric (AE) effect, which is spatially confined to the ultrasound focus. Data from two experiments are presented. A 540 kHz ultrasonic transducer (f/#=1, focal length=90 mm, pulse repetition frequency=1600 Hz) was scanned over an isolated rabbit heart, perfused with excitation-contraction decoupler to significantly reduce motion while retaining electric function. Tungsten electrodes inserted in the left ventricles recorded simultaneously the AE signal and the low frequency electrocardiogram (ECG). UCSDI displayed spatial and temporal patterns consistent with the spreading activation wave. The propagation velocity estimated from UCSDI was 0.25plusmn0.05 mm/ms, comparable to the values obtained with the ECG signals. The maximum AE signal-to-noise ratio after filtering was 18 dB, with an equivalent detection threshold of 0.1 mA/cm2. This study demonstrates that UCSDI is a potentially powerful technique for mapping current flow and biopotentials in the heart.
Keywords :
acoustoelectric effects; bioelectric potentials; biomedical electrodes; biomedical ultrasonics; blood vessels; cardiovascular system; electrocardiography; muscle; spatiotemporal phenomena; ECG signals; UCSDI; ablation procedures; acousto-electric effect; activation wave spreading; cardiac current mapping; excitation-contraction decoupler; frequency 540 kHz; heart arrhythmias; heart biopotential; isolated rabbit heart; left ventricles; live heart; low-frequency electrocardiogram; pressure-induced change; propagation velocity estimation; spatial patterns; spatial resolution; temporal patterns; tungsten electrodes; ultrasonic transducer; ultrasound current source density imaging; Conductivity; Electrocardiography; Focusing; Frequency; Heart; Rabbits; Spatial resolution; Tungsten; Ultrasonic imaging; Ultrasonic transducers; acousto-electric; arrhythmia; cardiac mapping; electrocardiology; electromechanical imaging;
Conference_Titel :
Ultrasonics Symposium, 2008. IUS 2008. IEEE
Conference_Location :
Beijing
Print_ISBN :
978-1-4244-2428-3
Electronic_ISBN :
978-1-4244-2480-1
DOI :
10.1109/ULTSYM.2008.0181