Feasibility of Ultra-Dilute Iodine Contrast Agent in Dual-Layer Spectral CT for Pulmonary Artery Imaging

This study aimed to investigate the clinical feasibility of using an ultra-dilute, low-concentration iodine contrast agent in combination with duallayer spectral computed tomography (CT) for pulmonary artery imaging.

A total of 143 patients who underwent CT pulmonary angiography (CTPA) between May 2024 and May 2025 were enrolled. After excluding 19 patients with suboptimal image quality due to technical factors, 124 patients were included in the final analysis (spectral group: n = 64; control group: n = 60). Patients were assigned to either a spectral group (100 kV, 160 mgI/mL contrast, 25 mL, 2.5 mL/s) or a control group (120 kV, 350 mgI/mL contrast, 35 mL, 4 mL/s). In the spectral group, images were reconstructed using conventional CT and virtual monoenergetic imaging at 40, 70, and 110 keV. The control group underwent conventional CT imaging only. Image quality, CT attenuation values, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and radiation doses were assessed and compared between the two groups.

In the spectral group, 40 keV monoenergetic images yielded the highest CT values, SNR, and CNR for all pulmonary artery branches. The control group demonstrated superior image quality on conventional CT and at higher monoenergetic levels (70 and 110 keV), with statistically significant differences (P < 0.05). However, no significant differences were observed between the 40 keV spectral images and the control group. Subjective image quality scores were significantly lower at 70 and 110 keV, but comparable at 40 keV (P > 0.05).

The use of an ultra-low concentration iodine contrast agent (160 mgI/mL) combined with dual-layer spectral CT provides diagnostic image quality equivalent to that of conventional protocols, while reducing the iodine load by 67% (to 4 g per examination). This approach reduces iodine load while maintaining diagnostic image quality, although its effect on renal safety requires further clinical validation.

Dual-layer spectral CT combined with 40 keV virtual monoenergetic imaging allowed pulmonary artery imaging with markedly reduced iodine load while maintaining diagnostic image quality comparable to that of the conventional protocol.