High speed optical observations of contrast agent dynamics and breakage

Improved diagnostic decisions have been made possible with new imaging methods using contrast agent. Since it is well known that contrast agents are destroyed by ultrasound, extremely low acoustic pressures were applied to achieve enhanced contrast image quality with minimal destruction. However destruction of contrast microbubbles is not necessary undesirable. We investigate in this experimental study the destruction of PB127 contrast agent. This is accomplished using an ultra fast camera Brandaris. The measurements were performed using a sine wave burst of 10 cycles at 1.7 MHz. Different acoustic pressures were applied and various microsphere sizes were examined. The results show that below a certain acoustic pressure, the microbubbles hardly oscillate and remain intact. Above the threshold, the microbubbles are destroyed. The optical observations revealed that the destruction of the microspheres is characterized by shell rupture and gas release. The release of the gas gives rise to new free microbubbles that last for a few milliseconds and then disappear due to dissolution. These optical recordings are important to investigate contrast bubble destruction and can help in optimizing this process. Indeed, bubble disruption is an essential component for perfusion quantification with microbubbles in addition to drug delivery applications and pressure measurements.