purposes so of course in those days there was no concept of tomography right that was not you mean in the lexicon it's a totally new modern concept we're using this very old physics with a very new modern imaging concept to form a new imaging modality a very simple analogy I can think of for photoacoustic CT is how can we pinpoint a single sound source single point sound source like a thunderbolt so when we see the lining we can reset our stopwatch that would be our time zero when we hear the sounder we can record a time delay t1 multiply