point source we're gonna use light to generate a volumetric 3d complex source we don't know the exact source distribution because the source distribution is the image we're after so we have to use more than three detectors but this gives you the basic concept at the simplest level so for photoacoustic CT the first thing we do is to expand the laser beam very different from a common use of laser where you want to use a very high intensity to drill a piece of metal for example so when we talk about laser you say well that would