DECOMPRESSION-INDUCED TISSUE BUBBLES DETECTED USING DUAL-FREQUENCY ULTRASOUND

• Published in: Aviation, space, and environmental medicine space, and environmental medicine, 2009-03, Vol.80 (3), p.290-290
• Main Authors: Donoghue, T G, Bollinger, B R, Wilbur, J C
• Format: Article
• Language: English
• ISSN: 0095-6562

INTRODUCTION: Venous gas emboli can be detected easily in the bloodstream using existing methods. No method currently exists to detect decompression-induced stationary bubbles in tissue. The purpose of this study was to determine if dual frequency ultrasound could detect these bubbles. METHODS: Dual-frequency ultrasound bubble detection exploits the fact that resonating bubbles act as nonlinear mixers. Bubbles are driven with two frequencies: a lower 'pump' (set to the resonant frequency of the desired bubble size) and a higher 'image' frequency. A bubble of the resonant size emits the sum and difference of the two transmitted frequencies. For this study we used a pump of 2.25 mHz and an image of 5.0 mHz, which detects bubbles of approximately 10 microns in diameter. Four anesthetized swine were pressurized at 4.5ATA for 2hrs and decompressed over 5 minutes. Four sites on the thigh of each swine were monitored with standard and dual frequency ultrasound before and after the dive. Each site was scanned using clinical 2-D ultrasound to insure that no bones or major vessels were in the measurement volume. A single sham dive was also performed to examine any possible impact of the anesthesia or other experimental parameters on the detected bubble signal.