Acoustic Imaging of the Human Chest

A novel method for acoustic imaging of the human respiratory system is proposed and evaluated. The proposed imaging system uses simultaneous multisensor recordings of thoracic sounds from the chest wall, and digital, computer-based postprocessing. Computer simulations and recordings from a life-size gelatin model of the human thorax are used to evaluate the system in vitro. Spatial representations of thoracic sounds from 8-microphone and 16-microphone recordings from five subjects (four healthy male adults and one child with lung consolidation) are used to evaluate the system in vivo. Results of the in vitro studies show that sound sources can be imaged to within 2 cm, and that the proposed algorithm is reasonably robust with respect to changes in the assumed sound speed within the imaged volume. The images from recordings from the healthy volunteers show distinct patterns for inspiratory breath sounds, expiratory breath sounds, and heart sounds that are consistent with the assumed origin of the respective sounds. Specifically, the images support the concept that inspiratory sounds are produced predominantly in the periphery of the lung while expiratory sounds are generated more centrally. Acoustic images from the subject with lung consolidation differ substantially from the images of the healthy subjects, and localize the abnormality. Acoustic imaging offers new perspectives to explore the acoustic properties of the respiratory system and thereby reveal structural and functional properties for diagnostic purposes.