GSI (Gemstone Spectral Imaging)
GE HealthCare's fast-kVp-switching dual-energy CT approach. The X-ray tube rapidly alternates between low-energy (typically 40 kVp) and high-energy (typically 120 kVp) on a view-by-view basis, acquiring both energies within the same rotation. Post-processing material-decomposition reconstruction produces iodine maps, virtual non-contrast images, virtual monoenergetic images (40–140 keV), effective-Z maps, and uric-acid / calcium differentiation.
Why it matters to buyers: GSI is architecturally distinct from Siemens dual-source (two tubes / two detectors) or Philips dual-layer detector approaches to spectral CT. Single-tube, single-detector hardware — simpler service but requires the fast-afterglow Gemstone detector to resolve the rapid kVp alternation.
Why it matters to engineers: GSI is a Gemstone-detector-dependent capability. Loss of GSI on a Discovery CT750 HD or Revolution HD points to tube kVp-switch electronics or detector-timing service items.