K-Edge Imaging Using a Clinical Dual-Source Photon-Counting CT System

To evaluate the feasibility and performance of K-edge imaging of iodine (I) and gadolinium (Gd) on a clinically available photon-counting computed tomography (PCCT) system.

A dual-source clinical PCCT scanner with four energy thresholds (20, 55, 72, 90 keV) was used to scan phantoms containing pure and mixed solutions of I and Gd across multiple concentrations (1-10 mg/mL) and radiation doses (1-8 mGy). Multi-material decomposition was performed using a calibration-based, image-domain algorithm to generate material-specific maps. Quantitative accuracy was assessed using Bland-Altman analysis and contrast-to-noise ratio (CNR), while noise and bias trends were statistically analyzed using non-parametric tests.

K-edge imaging was successfully achieved on a clinical PCCT system with accurate decomposition of I and Gd across varying concentrations, solution types (pure/mixed), and dose levels. Quantitative bias was significantly influenced by radiation dose, concentration, and solution type (p < 0.0004). Increased radiation dose and contrast concentration improved quantification accuracy, with maximum bias reductions of 0.9 (I) and 0.3 mg/mL (Gd). CNR correlated linearly with concentration (R² > 0.99) and moderately with dose (R² = 0.85-0.94), achieving peak values of 13 (I) and 16 (Gd) at 8 mGy. Mixed solutions showed reduced performance compared to pure solutions, i.e., CNR of 5 mg/mL Gd solutions increased by 0.6 per mGy in pure solutions while by 0.5 per mGy in mixtures. Noise was dependent on dose but not on concentration or solution type.

This study establishes the feasibility of K-edge imaging using a clinical PCCT system and demonstrates accurate, simultaneous decomposition of I and Gd in pure and mixed solutions. These findings support the clinical translation of K-edge imaging and highlight PCCT's potential for advanced dual-contrast and molecular imaging applications.