What are the technical factors involved in the use of microbubble contrast ultrasound?

The microbubble contrast ultrasound technique is used to increase the scattering of ultrasound in the blood, and can be used as a contrast medium.
Microbubble encapsulated agents are the most likely to be successfully used as ultrasound signal enhancers.
The microbubbles have a fundamental resonance frequency of a few megahertz, making them suitable for medical ultrasound systems.
The second harmonic frequency can be used to enhance the signal of the microbubble contrast agent.
The microbubble contrast agents are very sensitive to the ultrasound beam, and a higher transmitted energy does not necessarily produce a stronger ultrasound signal.
Some microbubble contrast agents require high acoustic pressures to enhance the backscatter due to bubble destruction.