Extracellular Volume Fraction Derived From Dual-Layer Spectral Detector Computed Tomography for Diagnosing Cervical Lymph Nodes Metastasis in Patients With Papillary Thyroid Cancer: A Preliminary Study

OBJECTIVES: The current study evaluates the performance of dual-energy computed tomography (DECT) derived extracellular volume (ECV) fraction based on dual-layer spectral detector CT for diagnosing cervical lymph nodes (LNs) metastasis from papillary thyroid cancer (PTC) and compares it with the value of ECV derived from conventional single-energy CT (SECT). METHODS: One hundred and fifty-seven cervical LNs (81 non-metastatic and 76 metastatic) were recruited. Among them, 59 cervical LNs (27 non-metastatic and 32 metastatic) were affected by cervical root artifact on the contrast-enhanced CT images in the arterial phase. Both the SECT-derived ECV fraction (ECV(S)) and the DECT-derived ECV fraction (ECV(D)) were calculated. A Pearson correlation coefficient and a Bland–Altman analysis were performed to evaluate the correlations between ECV(D) and ECV(S). Receiver operator characteristic curves analysis and the Delong method were performed to assess and compare the diagnostic performance. RESULTS: ECV(D) correlated significantly with ECV(S) (r = 0.925; p <0.001) with a small bias (−0.6). Metastatic LNs showed significantly higher ECV(D) (42.41% vs 22.53%, p <0.001) and ECV(S) (39.18% vs 25.45%, p <0.001) than non-metastatic LNs. By setting an ECV(D) of 36.45% as the cut-off value, optimal diagnostic performance could be achieved (AUC = 0.813), which was comparable with that of ECV(S) (cut-off value = 34.99%; AUC = 0.793) (p = 0.265). For LNs affected by cervical root artifact, ECV(D) also showed favorable efficiency (AUC = 0.756), which was also comparable with that of ECV(S) (AUC = 0.716) (p = 0.244). CONCLUSIONS: ECV(D) showed a significant correlation with ECV(S). Compared with ECV(S), ECV(D) showed comparable performance in diagnosing metastatic cervical LNs in PTC patients, even though the LNs were affected by cervical root artifacts on arterial phase CT.