CT of the Abdomen for the Study of Hepatocellular Carcinoma: Examination Technique with Dual Energy GSI Protocol

The CT examination after the administration of a contrast medium has, since its inception, been one of the reference methods for diagnosing hepatic HCC (Hepatocellular Carcinoma). Thanks to the intravenous administration of iodinated contrast and the application of appropriately timed study protocols, it is possible to detect the presence of the characteristic post-contrast pattern of neoplastic nodules. Gemstone Spectral Imaging (GSI) is a new application of dual-energy CT technology (Dual Energy Computed Tomography, DECT) that uses a rapid change in kilovoltage (from 80 to 140 kVp) to almost simultaneously acquire two samples at different energy levels, making it possible to obtain data related to the density of different substances, which are then used to separate materials and produce monochromatic spectral images. The principle behind DECT technology aims to detect density differences between substances based on differences in photon attenuation coefficients at different energy levels. GSI represents an evolution of the current DECT with two X-ray tubes and two detectors, as it uses a single source that, thanks to the rapid transition from low kVp to high kVp energy and a detector system with at least 128 layers, allows data to be acquired very quickly, decomposing matter into its different components such as calcium, iodine, and water.