Study objectives: A novel method for acoustic imaging of the human respirat
ory system is proposed and evaluated.
Design: The proposed imaging system uses simultaneous multisensor recording
s of thoracic sounds from the chest wall, and digital, computer-based postp
rocessing. Computer simulations and recordings from a life-size gelatin mod
el of the human thorax are used to evaluate the system in vitro. Spatial re
presentations of thoracic sounds from 8-microphone and 16-microphone record
ings from five subjects (four healthy male adults and one child with lung c
onsolidation) are used to evaluate the system in vivo.
Results: Results of the in vitro studies show that sound sources can be ima
ged to within 2 cm, and that the proposed algorithm is reasonably robust wi
th respect to changes in the assumed sound speed within the imaged volume.
The images from recordings from the healthy volunteers show distinct patter
ns for inspiratory breath sounds, expiratory breath sounds, and heart sound
s that are consistent with the assumed origin of the respective sounds. Spe
cifically, the images support the concept that inspiratory sounds are produ
ced predominantly in the periphery of die lung while expiratory sounds are
generated more centrally. Acoustic images from the subject with lung consol
idation differ substantially from the images of the healthy subjects, and l
ocalize the abnormality.
Conclusions: Acoustic imaging offers new perspectives to explore the acoust
ic properties of the respiratory system and thereby reveal structural and f
unctional properties for diagnostic purposes.