I'll give you more demonstrations later on to make sure we understand the concept photoacoustic very much like x-ray CT there's also photoacoustic CT we have different geometries I'm going to talk about circular geometry first photo acoustics as a physical phenomenon has been around for over 100 years in fact Alexander Graham Bell first reported photo acoustics he actually invented the concept of photo phone right very interestingly this paper was published only a few years after the first telephone was built he had a site