Assessment of Diagnostic Accuracy and Measurement Reliability of Low-keV Virtual Monoenergetic Dual-energy CT in The Liver Metastases of Colorectal Cancer: A Prospective, Imaging-Reference Study

Objective: To assess the value of low-keV virtual monoenergetic imaging (VMI) from dual-energy CT (DECT) for detecting liver metastases of colorectal cancer (CRC) and for evaluating treatment response. Materials and Methods: Patients diagnosed with CRC who had liver metastases (CRLM) were prospectively enrolled. All underwent DECT, followed by magnetic resonance imaging (MRI) used as the gold standard. DECT datasets were reconstructed as standard linearly-blended (M_0.6) images to simulate contrast-enhanced CT (CECT) and as VMI at 10-keV intervals (40–70 keV). Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were measured. Radiologists independently assessed image quality, lesion delineation, and image noise using a 5-point Likert scale. Per-lesion sensitivity, specificity, and detection rates were calculated.Treatment response was evaluated using RECIST 1.1. Results: Thirty-five patients (125 liver metastases) were enrolled. 40-keV VMI provided the best CNR (6.2 ± 4.3, p < 0.01) and SNR (15.5 ± 9.5, p < 0.01), with AUCs of 0.974 for SNR and 0.966 for attenuation. It outperformed M_0.6 images for detecting lesions ≤10 mm (86.7% vs. 60.0%, p < 0.05). Image quality of 60-keV VMI was equivalent to M_0.6 (median 5, p > 0.05). Lesion delineation was optimal with 40-keV and 50-keV VMI (median 5). Image noise was lowest with 60-keV VMI (median 4, p < 0.01). Lesion size reduction was comparable between MRI and DECT (5.2 ± 5.5 mm vs. 4.6 ± 6.2 mm, p = 0.41). Conclusion: Low-keV VMI improves the diagnostic accuracy of liver metastases of CRC compared to CECT, while maintaining measurement reliability in treatment-response assessment.