The assessment of intracranial bleeding with virtual unenhanced imaging by means of dual-energy CT angiography

The purpose of this study was to assess virtual unenhanced brain computed tomography (CT) images obtained by dual-energy CT angiography (CTA) for the detection of intracranial bleeding. In total, 25 patients were included in the study (average age 53.2 years, range 25–75 years, 14 male, 11 female), all with intracranial bleeding on unenhanced brain CT and who underwent additional CTA performed on a dual-source CT in a dual-energy acquisition mode. The two X-ray tubes were operated at 140 and 80 kV, respectively. Data were analyzed using dual-energy evaluation software. Virtual unenhanced images were calculated by removing the relative iodine content from each voxel. The virtual unenhanced images were evaluated by a radiologist blinded to the findings of the conventional images related to the presence of intracranial bleeding. The image quality and contrast-to-noise ratio (CNR) between bleeding and brain tissue were assessed. The virtual image quality was found to be sufficient in 96%. The agreement in detection of intracranial bleeding on virtual and conventional unenhanced images reached 96% in per-lesion analysis and 100% in per-patient analysis. The averaged CNR reached 2.63 in virtual unenhanced images and 3.27 in conventional. Virtual unenhanced images are sufficient for the detection of intracranial bleeding.