Example substances and methods relating to contrast agents are provided. An example method includes combining a surface active protein, a stabilizer, and a dispersion media to form a solution. The example method may further include aerating the solution in a gas to form a contrast agent comprising at least one microbubble formed from an interaction between the surface active protein and the stabilizer. A diameter of the at least one microbubble may be proportional to a pressure of an external environment of the contrast agent, such that measurement of the diameter may allow for measurement of the pressure.
