Improving spectral CT image quality of thyroid nodules

Objective: To investigate the optimal monochromatic spectral CT for improving image quality of thyroid nodules. Methods: 45 patients with histologically proven thyroid nodules underwent contrast-enhanced cervical spectral CT in the arterial and venous phases to obtain the images of 70 keV and optimal keV (Opti keV) photon energies. The image noise, contrast-to-noise ratio (CNR), and qualitative scores of the two photon energy groups in each phase were compared using Wilcoxon test. Visualization of the margin, complete or interrupted enhancing capsule, and microcalcifications of the nodules was also compared using McNemar's test. Results: Of 129 thyroid nodules detected, 66 were benign and 63 were malignant. The optimal energy level was 61.16 #+-# 5.07 keV in the arterial phase and 61.87 #+-# 4.28 keV in the venous phase. In both phases, the image noise, CNR and qualitative score of Opti keV group were significantly greater than that of 70 keV group (P = 0). Visualization of the margin, microcalcifications, complete and interrupted enhancing capsules of the thyroid nodules of Opti keV group was also significantly better (P = 0). Conclusion: Opti keV spectral CT is superior to 70 keV for assessing benign and malignant thyroid nodules. (authors)