Enabling Low-Radiation-Dose and Low-Contrast-Volume Renal Artery CT Angiography with Dual-Layer Spectral Detector CT-Derived Virtual Monoenergetic Imaging and Model-Based Iterative Reconstruction

Objectives: To evaluate the efficacy of Virtual Monochromatic Imaging (VMI) and Model-based Iterative Reconstruction (IMR) derived from Dual-Layer Spectral Detector CT (DLCT) in reducing radiation dose and contrast agent volume during renal CT angiography (CTA). Methods: Ninety-four patients with suspected renal artery disease were prospectively enrolled and randomized into a full-dose group and a dual-low-dose group (n=47 each). Scans were performed on a DLCT system with Automatic Tube Current Modulation. The full-dose group received 1.5 ml/kg iohexol (300 mgi/ml) with a Dose Right Index (DRI) of 22 and hybrid iterative reconstruction(Group A).The dual-low-dose group received 0.75 ml/kg iohexol with a DRI of 10; images were reconstructed using VMI at 70, 60, 50, and 40 keV (Groups B–E) and IMR (Group F). Quantitative metrics (CT value, noise, SNR, CNR) and Qualitative image quality were compared among groups. Results: The dual-low-dose protocol achieved 65% and 50% reductions in effective dose and iodine load, respectively. Groups D (50 keV) and F (IMR) provided optimal reconstructions,followed by Group E. SNR and CNR in Groups D–F were significantly higher than in Group A ( P <0.05). While Group F exhibited the lowest noise ( P <0.05), its SNR and CNR were comparable to Group D ( P >0.05). Subjectively, vessel contrast, artifacts, and diagnostic confidence in Groups D and E matched or exceeded Group A. Diagnostic confidence in Group F was superior to Group E ( P <0.05) and equivalent to Group D ( P >0.05). Conclusions: DLCT-based renal CTA utilizing 40–50 keV VMI or IMR reconstruction maintains or improves image quality while significantly reducing radiation and contrast burden compared to standard protocols with hybrid iterative reconstruction.