Dual-Source Dual-Energy Thin-Section CT Combined with Small Field of View Technique for Diagnosing Small Lymph Node in Thyroid Cancer

Abstract

Background To evaluate the diagnostic performance of quantitative special CT parameters derived from dual-source dual-energy CT at small field of view (FOV) for small lymph node metastasis in thyroid cancer. Methods This was a retrospective study. From 2016 to 2019, 280 patients with thyroid disease underwent thin-section dual-source dual-energy thyroid CT and thyroid surgery. The data of patients with lymph nodes having a short diameter of 2-6 mm were analyzed. The targeted lymph nodes were sketched, their quantitative dual-energy CT parameters were measured, and all parameters between metastatic and nonmetastatic lymph nodes were compared. These parameters were then fitted to univariable and multivariable binary logistic regression models. The diagnostic role of spectral parameters was analyzed by receiver operating characteristic curves and compared with the McNemar test. Small FOV CT images and a mathematical model were used to judge the lymph nodes status respectively and then compared with pathological results.Results Of the 216 lymph nodes investigated in this study, 52.3% and 23.6% had a short diameter of 2-3 mm and 4 mm, respectively. Multiple quantitative CT parameters were found to be significantly different between benign and malignant lymph nodes and binary regression analysis was performed. The mathematical model was: p=ey/(1+ ey), y= = -23.119+0.033×precontrast electron cloud density+0.076×arterial phase normalized iodine concentration+2.156×arterial phase normalized effective atomic number -0.540×venous phase slope of the spectral Hounsfield unit curve +1.676×venous phase iodine concentration. This parameter model has an AUC of 92%, with good discrimination and consistency, and the diagnostic accuracy was 90.3%. The diagnostic accuracy of CT image model was 43.1%, and for lymph nodes with short-diameter 2-3 mm, the diagnostic accuracy was 22.1%.Conclusions Parameter model show higher diagnostic accuracy than CT image model for diagnosing small lymph node metastasis in thyroid cancer, and quantitative dual-energy CT parameters were very useful for small lymph nodes that were difficult to be diagnosed only on conventional CT images.Trial registration This study is retrospectively registered, and we have registered a prospective study (Registration number: ChiCTR2000035195;http://www.chictr.org.cn)