Comparison of image quality of 40 keV virtual monoenergetic images of vertebral arteries using DLIR and ASIR-V algorithms under a dual-low scanning protocol.

Objective: This study aims to compare the image quality of 40 keV Virtual Monoenergetic Images (VMI) of the vertebral artery (VA) reconstructed using two algorithms, Deep Learning Image Reconstruction (DLIR) and Adaptive Statistical Iterative Reconstruction (ASIR-V), under a dual-low scanning protocol, which simultaneously reduces both the radiation dose and the contrast agent dose during the CT scanning process.

Methods: A total of 88 patients were randomly assigned to an experimental group (n = 44) and a control group (n = 44). Both groups underwent dual-energy carotid CT angiography (DE-CTA) with a contrast agent dose of 0.5 ml/kg. The experimental group [Noise Index (NI) = 11.0] used DLIR at high-strength (DLIR-H) and medium-strength setting (DLIR-M), along with Adaptive Statistical Iterative Reconstruction algorithm set at 50 % strength (ASIR-V 50 %), while the control group (NI = 4.0) used ASIR-V 50 %. Image quality was evaluated both objectively [using CT values, noise, Signal-to-Noise Ratio (SNR), and Contrast-to-Noise Ratio (CNR)] and subjectively [using a 5-point scale for image noise, vascular contours, curve planar reformation (CPR), and overall image quality].

Results: The experimental group demonstrated a 44.4 % reduction in effective radiation dose compared to the control group (0.85 mSv and 1.53 mSv, respectively, P < 0.001). DLIR algorithms, especially DLIR-H, significantly reduced image noise and improved both SNR and CNR compared to ASIR-V 50 % (P < 0.01). Subjective evaluation revealed that more than 70 % of the images in the experimental group scored above 4 points, indicating excellent image quality. Furthermore, DLIR-H outperformed both ASIR-V 50 % and DLIR-M in both objective and subjective image quality assessments (P < 0.01).

Conclusion: The DLIR algorithm, particularly DLIR-H, significantly improves the quality of 40 keV VMI of the vertebral artery under a dual-low scanning protocol. DLIR-H provides superior image quality with reduced radiation exposure, making it a promising option for clinical applications in patients with posterior circulation ischemic stroke. These findings are important for clinical practice as they suggest that DLIR-H can enhance diagnostic accuracy while minimizing risks associated with radiation exposure, particularly in vulnerable patient populations.