A non-invasive, in-vivo, bubble sizing instrument

Creare has developed and demonstrated a non-invasive, in-vivo instrument for detecting, classifying, and sizing gaseous emboli which can result in decompression sickness. The instrument consists of a low-frequency pump transducer to excite the fundamental vibration mode of the bubbles and a high-frequency imaging transducer to observe the resonance. Because the bubbles act as nonlinear mixers, sidebands will be present in the high-frequency return signal at plus and minus the pump frequency, if and only if, there is a resonant bubble. The instrument was extensively tested in vitro over a wide range of bubble size distributions. Preliminary experiments were performed on an animal model to demonstrate the device in vivo.