Abstract: A radiation source which generates a radiation cone-beam (14) and a two-dimensional radiation detector are spiralled continuously around and longitudinally relative to an imaging volume. Image data from the two-dimensional display is reconstructed (30.sub.1, 30.sub.2, . . . 30.sub.n) into a volumetric, physiological image stored in a subject memory (32). During an interventional surgical procedure with a surgical instrument (42), the x-ray source is gated to operate intermittently, e.g., at 60.degree. angular intervals, at a reduced radiation intensity by an x-ray tube control (40). The additional data is reconstructed into a three-dimensional image representation of the surgical instrument and stored in an instrument memory (34). An operator image selection processor (60) causes data retrieval circuits (62a, 62b) to retrieve like slices or other image representations from the subject and instrument memories.