Lower extremity CT angiography at 80 kVp using iterative model reconstruction

To evaluate the use of 80 kVp and iterative model reconstruction (IMR) in lower extremity computed tomography angiography (CTA).

Sixty patients were randomly assigned to Group A or Group B (both n=30) to further undergo CTA. Group A received Protocol 1 (P1) with 120 kVp, 180mAs, and 100mL of contrast agent with filtered back-projection (FBP). Group B received Protocol 2 (P2) and Protocol 3 (P3) with 80 kVp, 140mAs and 75mL of contrast agent with hybrid iterative reconstruction (P2) and IMR (P3). Mean intravascular attenuation (MIA), image noise, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) were compared. Radiologists assessed image quality on a 5-point scale, and radiation was compared between both groups.

Group A had 9 men and 21 women (mean age, 68.2±9.3 years [range: 53-85 years]), and Group B had 20 men and 10 women (mean age, 64.8±10.4 years [range: 37-81 years]). The MIA of P2 and P3 were significantly larger than that of P1 (P<0.01). The CNR and SNR of P3 were significantly higher than those of P1 and P2 (P<0.01). The interobserver agreement had Kappa values of 0.78, 0.77, and 0.81 for P1, P2, P3, respectively. The mean CT volume dose index and dose-length product of Group B were lower than those of Group A (P<0.01).

Lower extremity CTA using 80 kVp and IMR is useful for lower radiation and contrast agent dose while preserving image quality. IMR can also provide better image quality for small-caliber vessels below the knee than HIR.