>>Rather, what bridgeofsighs is seeking (if I understand him correctly) is the growth in procedures conducted by machines that have been installed for more than one year.<<
I don't have that number. Furthermore it isn't clear what bridgeofsighs would do with that number if he had it.
However new systems aren't used nearly as often as systems which have been installed for more than one year, so one could obtain a *crude* estimate of 'same store procedures' by simply taking the total number of procedures and dividing it by the installed base a year prior.