Array phonocardiography

The feasibility of applying passive listening array technology to the detection and localization of audible acoustic signals in the human body is discussed. A primacy clinical objective is the low cost, noninvasive early diagnosis of coronary artery disease (CAD). Referred to as array phonocardiography, the technique uses an array of vibration sensors placed noninvasively on the external chest wall. A wavespeed dispersion curve permits focusing of a scanning beam to an array near field focal point that is scanned over a desired volume to form an intensity image. A model for blood flow induced vibrations of a diseased coronary artery is used to compare with experimental, in vitro, results using a urethane phantom. A turbulence source can be located to within 1 cm. Imaging is performed using both a time delay-and-sum conventional beamformer (CBF) and a reduced rank adaptive beamformer (rrABF). The performance of the rrABF is sensitive to the spatial extent of the radiating near field source, however, the imposition of a spatial gain constraint mitigates the problem.