Successful use of non-contrast dual energy computed tomography in patients with differentiated thyroid cancer

Differentiated thyroid cancer (DTC) is the most commonly diagnosed endocrine cancer. Diagnosis of DTC metastases is possible with the use of ultrasound, RAI scintigraphy, [¹⁸F]FDG PET/CT, or contrast-enhanced CT; however, the use of iodine contrast factors (ICF) delays potential RAI treatment. Dual energy computed tomography (DECT) is a variant of computed tomography that enables the detection and calculation of iodine concentration in tissues. The study aimed to evaluate the potential use of non-contrast DECT in diagnosing DTC metastases.

This prospective study enrolled 37 patients who had undergone thyroidectomy for DTC and were found to have lesions suspected of being metastatic. DECT was performed at least six months after the last administration of RAI or ICF. Group differences were analyzed using statistical tests, including the Student's t-test and the Mann-Whitney U test. Receiver operating characteristic (ROC) curves were utilized to assess the sensitivity and specificity of selected parameters.

In 31 of 37 patients, non-contrast DECT confirmed increased accumulation of endogenous iodine. Per patient, DECT sensitivity was 93.5%, specificity was 100%, positive predictive value (PPV) was 100%, and negative predictive value (NPV) was 71.4%. Statistically higher values of iodine concentration (IC), effective atomic number (Z_eff), and Hounsfield Unit (HU) were observed for DTC metastases compared to normal lymph nodes. The area under the curve (AUC) for endogenous iodine concentration was 0.992, and a threshold of endogenous IC >250 µg/cm3 provided a sensitivity of 96.6% and a specificity of 87.0% for detecting DTC metastases.

Non-contrast DECT is useful in the diagnosis of DTC metastases, demonstrating high sensitivity and specificity. A key advantage is the lack of necessity for ICF, which prevents delay in potential radioiodine therapy and is safer for patients with an allergy to such factors.