Characteristics of incidentally found thyroid nodules in computed tomography: comparison with thyroid scintigraphy

In our daily experience, the differentiation between a cold and hot nodule is a very important factor for further clinical management of the patient. In this study, we compared the characteristics of incidentally found thyroid nodules detected on computed tomography (CT) to thyroid scintigraphy (TS).

Diagnostic reports from chest CT with intravenous contrast and TS examinations performed from January 2013 to January 2016 were analyzed retrospectively. We identified 70 subjects: 50 with thyroid nodules and 20 control subjects without thyroid nodules. The examination time of the TS was a minimum of two to four months after a chest CT. Chest CTs were performed in the arterial phase after the application of contrast media.

Patients with a cold nodule had a significantly lower Hounsfield Unit (HU) Nodule(N)/Parenchyma (P) ratio values than the patients with a hot or warm nodule (P < 0.05). The cut-off HU N/P ratio value with the highest sum of sensitivity and specificity for the prediction of a functioning nodule was 69 (95% CI: 0.79-0.95).

Our results imply that the HU N/P ratio of the thyroid nodule on the chest CT should be taken into account to assess the functionality of the nodule. A lower HU N/P ratio should alert the radiologist or nuclear medicine physician to the possibility that the nodule might be cold and thus more prone to malignancy.