Feasibility of very low iodine dose aortoiliac CT angiography using dual-source photon-counting detector CT

Purpose: To evaluate the feasibility of aortoiliac CT-Angiography (CTA) using dual-source photon-counting detector (PCD)-CT with minimal iodine dose. Methods: This IRB-approved, single-center prospective study enrolled patients with indications for aortoiliac CTA from December 2022 to March 2023. All scans were performed using a first-generation dual-source PCD-CT. Images were acquired with fast pitch and full spectral capabilities (collimation 144 x 0.4 mm). The contrast protocol included a mixture of sodium chloride and iodinated contrast agent (Iopromide, total iodine dose: 9.5-9.8 g). Virtual monoenergetic images (VMIs) were reconstructed at 40, 50, 60, and 68 keV. Two blinded radiologists evaluated image quality on a 4-point scale. Attenuation was measured across eight regions in the aorta and iliac arteries, and contrast-to-noise ratio (CNR) was calculated. Statistical comparisons were performed using repeated measures ANOVA and Bonferroni post-hoc tests. Results: The final cohort consisted of 39 subjects (mean age: 69.6 +/- 9.6 years; 30.8 % female). VMI at 40 keV provided significantly higher attenuation: 478 +/- 114 HU, compared to 50 keV (331 +/- 74 HU), 60 keV (241 +/- 51 HU), and 68 keV (190 +/- 48 HU) (p < 0.01). This translated in increased CNR for 40 keV reconstructions (11.8 +/- 3.9), followed by 50 keV (9.1 +/- 3.0), 60 keV (7.0 +/- 2.3), and 68 keV (6.1 +/- 1.9) (p < 0.01). Subjective image quality was rated excellent at 40 keV (4 [3,4]), though associated with highest noise (38 +/- 7.4 HU, p = 0.02). Conclusion: Aortoiliac CTA using dual-source PCD-CT at 40 keV achieved high attenuation and CNR, enabling effective imaging with only 9.8 g of iodine.