Quantitative Assessment of Thyroid Nodules Using Dual-Energy Computed Tomography: Iodine Concentration Measurement and Multiparametric Texture Analysis for Differentiating between Malignant and Benign Lesions

Abstract

Results: The 34 nodules comprised 14 benign nodules and 20 malignant nodules. Iodine content and Hounsfield unit curve slopes did not differ significantly between benign and malignant thyroid nodules (P = 0.480-0.670). However, significant differences in the texture features of monochromatic images were observed between benign and malignant nodules: histogram mean and median, co-occurrence matrix contrast, gray-level gradient matrix (GLGM) skewness, and mean gradients and variance of gradients for GLGM at 80 keV (P = 0.014-0.044). The highest AUC was 0.77, for the histogram mean and median of images acquired at 80 keV.

Conclusions: Texture features extracted from monochromatic images using DECT, specifically acquired at high keV, may be a promising diagnostic approach for thyroid nodules. A further large study for incidental thyroid nodules using DECT texture analysis is required to validate our results.

Figure 1

A representative iodine material decomposition image at 120 kVp with the largest region of interest in thyroid nodules selected to exclude cysts and overt calcifications (a) and Hounsfield unit curve slopes at 40 to 190 keV (b).

Figure 2

Segmentations of a thyroid nodule on monochromatic images at (a) 40 keV, (b) 60 keV, and (c) 80 keV were performed manually.

Figure 3

A 62-year-old man with a thyroid papillary carcinoma. On an axial image at 80 keV, a true positive was confirmed using texture features as follows: gray-level co-occurrence matrix (GLCM) mean at 80 keV (1071.9; cut-off value < 1080.9), GLCM median at 80 keV (1071.9; cut-off value < 1080.9) (a). Based on iodine concentration value (0.63 mg/ml) alone, a false negative was determined (b).

Figure 4

A 59-year-old female with a benign thyroid tumor (follicular adenoma). On an axial image at 80 keV, a true negative was confirmed using texture features as follows: gray-level co-occurrence matrix (GLCM) mean at 80 keV (1082.2; cut-off value > 1080.9), GLCM median at 80 keV (1094.2; cut-off value > 1080.9) (a). Based on iodine concentration value (0.3 mg/ml) alone, a false negative was determined (b).