Dual energy CT (DECT) of the liver: conventional versus virtual unenhanced images

To compare image quality and noise of conventional unenhanced (CU) and virtual unenhanced (VU) images in patients who underwent hepatic dual energy computed tomography (DECT) and to assess potential radiation dose reduction. Forty consecutive patients were studied. Mean CU and VU image quality and noise were analyzed by two blinded radiologists using a five-point grade scale. The effective radiation dose of a triple-phase protocol (CU, arterial and DE portal phases) were compared with that of a dual-phase protocol (arterial and DE portal phases). No significant difference in mean image quality was observed between VU (3.92 +/- 0.85) and CU images (4.20 +/- 0.72). A significant difference in mean image noise was observed between VU and CU (P < 0.01). The dose reduction achieved by omitting the unenhanced acquisition was 30.47 +/- 7.07% (P < 0.01). In 6 patients, a complete VU liver image was not obtained. VU images can be obtained with similar image quality as CU. This approach favors a reduction in patient's radiation exposure. Nevertheless, a complete abdominal DECT is possible only in patients with a low body mass index, due technical limitations of the present DECT systems.