Iodine, an essential trace element for the human body, is closely related to the thyroid and is essential for the synthesis of the thyroid hormones. Iodine deficiency or excess iodine can cause thyroid dysfunction [
1,
2], leading to abnormal iodine content in the thyroid tissues, which results in disorders of the thyroid and other organs of the body [
3‐
5]. The iodine intake levels of the thyroid and
in vivo storage concentrations can be evaluated by measurement of the iodine content of the thyroid tissue. These values can be used to determine whether the thyroid dysfunction is caused by iodine deficiency or excess, which is clinically significant in the diagnosis of thyroid diseases [
6]. Previously, the iodine content of the body was indirectly determined by the measurement of urine iodine levels [
7,
8] and thyroid iodine absorption rates [
9]. However, the iodine content of the thyroid glands cannot be measured by these methods. Thyroid iodine content can be determined by the conversion of thyroid CT values; however, X-rays, which are used to achieve excitation in this process, have a limited spectral energy range, which inevitably leads to inaccuracies in the CT values, thus affecting the results of quantitative diagnosis [
10,
11]. Gemstone energy spectrum CT is based on the differences in the X-ray attenuation coefficients of different materials. This technique can be used to obtain not only monoergic images, but also substance-separation images [
12,
13]. Iodine-based substance separation images are very sensitive to iodine deposition and exhibit good resolution of tissues such as the thyroid gland; they can, therefore, be used for the quantification of the thyroid iodine content. In the present study, the possibility of energy spectrum CT iodine-based substance-separation imaging completely or partly replacing the previous methods for the measurement of thyroid iodine content was evaluated.