Dual-frequency ultrasound detection and sizing of microbubbles for studying decompression sickness.

摘要

Decompression sickness (DCS, or the "Bends") is a condition that afflicts hundreds of divers each year and is cause for concern for both the Navy, the Air Force, and NASA. Despite the fact that bubble formation is the purported cause of DCS symptoms, little is known about the location of bubble formation and growth during and following decompression, mostly due to prior inability to noninvasively detect stationary microbubbles in tissue. The goal of this thesis was to validate dual-frequency ultrasound (DFU) as a tool with which to study bubble formation during and following decompression.;To demonstrate sizing ability, microbubbles were generated using a micropipette and allowed to rise through an alignment tube into a water tank, where they were simultaneously imaged with DFU and optical photography. The DFU results were used to create predicted bubble size distributions, which correlated well with the bubble size distributions determined visually.;To demonstrate the ability to detect stationary microbubbles in vivo, known concentrations of microbubbles of known size were injected transcutaneously into the thigh muscle of a swine model. DFU was used to probe for signals indicative of microbubbles prior to and following injection. Signals were significantly greater following injection for microbubble solutions of 107/mL and greater, demonstrating the ability of DFU to detect stationary microbubbles in vivo.;Decompression studies were performed on a swine model using a profile of 4.5 ATA for 2 hours followed by a 5-minute decompression. DFU was used to probe for the presence of microbubbles in the thigh prior to and for one hour following decompression. Detected signal following decompression was significantly greater than prior to compression, indicating the ability to detect decompression-induced microbubble formation.;The ability of DFU to provide bubble size information and to detect stationary microbubble formation following decompression was demonstrated. These capabilities provide a tool with which to study bubble formation and evolution during and following decompression.