Diagnostic imaging

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 (301, 302, ... 30n) 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 may be gated to operate intermittently, e.g., at 60 DEG angular intervals, at a reduced radiation intensity by an x-ray tube control (40). The additional data can be reconstructed into a three-dimensional image representation of the surgical instrument and stored in an instrument memory (34). An operator image selection processor (60) may be provided to cause data retrieval circuits (62a, 62b) to retrieve like slices or other image representations from the subject and instrument memories. The retrieved data may be combined (64) such that a resultant human-readable display (68) shows the instrument superimposed on the anatomical image. The surgical instrument volumetric image may be continuously updated such that the display represents a real time display of the surgical instrument illustrating its advancement through the imaging region.