A diagnostic imaging system (10) includes an x-ray source (16), which is rotated around an examination region (20) on a rotating gantry (14). A subject, disposed on a couch (30), is translated longitudinally through the examination region (20). The imaging system is standardized such that a common subassembly is adapted to receive a bore (24) of any selectable diameter. The common subassembly includes a stationary gantry (12) and a bearing race (52) supported by bearing members (50). Standard motor modules (28), standard power slip ring modules (56), and standard information transmission modules (58) are disposed about the race (52). The number of the standard modules (28, 56, 58) is specified by a user.