CT Venography for Deep Vein Thrombosis Using a Low Tube Voltage (100 kVp) Setting Could Increase Venous Enhancement and Reduce the Amount of Administered Iodine

OBJECTIVE To investigate the validity of the 100 kVp setting in CT venography (CTV) in the diagnosis of deep vein thrombosis (DVT), and to evaluate the feasibility of reducing the amount of administered iodine in this setting. MATERIALS AND METHODS After receiving the contrast medium (CM) of 2.0 mL/kg, 88 patients underwent CTV of the pelvis and lower extremities by using one of four protocols: Group A, 120 kVp setting and 370 mgI/mL CM; group B, 120 kVp and 300 mgI/mL; group C, 100 kVp and 370 mgI/mL; group D, 100 kVp and 300 mgI/mL. The groups were evaluated for venous attenuation, vein-to-muscle contrast-to-noise ratio (CNR(VEIN)), DVT-to-vein contrast-to-noise ratio (CNR(DVT)), and subjective degree of venous enhancement and image quality. RESULTS Venous attenuation and CNR(VEIN) were significantly higher in group C (144.3 Hounsfield unit [HU] and 11.9), but there was no significant difference between group A (118.0 HU and 8.2) and D (122.4 HU and 7.9). The attenuation value of DVT was not significantly different among the four groups, and group C had a higher absolute CNR(DVT) than the other groups. The overall diagnostic image quality and venous enhancement were significantly higher in group C, but there was no difference between groups A and D. CONCLUSION The 100 kVp setting in CTV substantially help improve venous enhancement and CNR(VEIN). Furthermore, it enables to reduce the amount of administered iodine while maintaining venous attenuation, as compared with the 120 kVp setting.