Optimized dual-energy CT protocol for inferior vena cava CT angiography using 60 keV virtual monoenergetic imaging and 60% ASIR-V

Objective To investigate the effects of a dual-energy CT (DECT) protocol combining virtual monoenergetic imaging (VMI) with adaptive statistical iterative reconstruction-V (ASIR-V) on image quality and radiation dose for inferior vena cava (IVC) CT angiography (CTA), and to compare the optimized protocol with a conventional 120 kVp protocol. Methods 120 consecutive patients undergoing IVC-CTA were enrolled and allocated sequentially to two groups ( n = 60 each). Group A underwent conventional 120 kVp scanning with 400 mgI/mL contrast medium at 1.5 mL/kg and 50% ASIR-V reconstruction. Group B underwent DECT (rapid 80/140 kVp switching) with 320 mgI/mL contrast medium at 1.2 mL/kg. In Group B, seven VMI datasets from 40 to 70 keV in 5 keV increments were first reconstructed with 50% ASIR-V. At 60 keV, images were reconstructed with filtered back projection (FBP; 0% ASIR-V) and ASIR-V levels from 20% to 100% in 20% increments. Objective image quality was assessed using CT attenuation, standard deviation (SD), background noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) at five venous levels. Two radiologists independently rated subjective image quality and diagnostic confidence on 5-point Likert scales. Dose-length product (DLP), effective dose (ED), contrast medium volume, and iodine intake were also recorded and compared between protocols. Results In Group B, with ASIR-V fixed at 50%, CT attenuation, SD, background noise, SNR, and CNR decreased progressively as VMI energy increased. Among the seven VMI levels, 60 keV achieved the highest subjective image-quality score (all P < 0.05). At 60 keV, increasing ASIR-V reduced vascular SD and background noise and increased SNR and CNR. The 60 keV VMI plus 60% ASIR-V combination (Group B1) achieved the highest subjective score. Compared with Group A, Group B1 had significantly higher IVC CT attenuation and background noise (both P < 0.001), but SNR, CNR, and subjective image-quality scores did not differ significantly (all P > 0.05). Diagnostic-confidence scores for thrombosis, luminal stenosis, post-filter placement, and normal IVC findings were similar between Groups A and B1 (all P > 0.05). Relative to Group A, Group B1 reduced contrast medium volume, iodine intake, and ED by approximately 20.0%, 36.0%, and 12.51%, respectively (all P < 0.001). Conclusion The DECT protocol combining 60 keV VMI with 60% ASIR-V provided a favorable balance of image quality for IVC-CTA. The optimized protocol achieved SNR, CNR, subjective image quality, and diagnostic confidence similar to those of the conventional 120 kVp protocol while reducing contrast medium volume, iodine intake, and effective radiation dose.