Abstract
BackgroundThyroid function in patients with Grave’s disease is usually evaluated by thyroid scintigraphy with radioactive iodine. Recently, dual-energy computed tomography (DECT) with two different energy X-rays can calculate iodine concentrations and can be applied for iodine measurements in thyroid glands. This study aimed to assess the potential use of DECT for the functional assessment of the thyroid gland.MethodsThirteen patients with Grave’s disease treated at our hospital from May to September 2015 were included in this retrospective study. Before treatments, all subjects had undergone both iodine scintigraphy [three and 24 h after oral administration of 123I (20 μCi)] and non-enhanced DECT. The region of interests (ROIs) were placed in both lobes of the thyroid glands, and CT values (HU: Hounsfield unit) and iodine concentrations (mg/mL) calculated from DECT images were measured. The correlation between CT values and iodine concentrations from DECT in the thyroid gland was evaluated and then the iodine concentrations were compared with radioactive iodine uptake ratios by thyroid scintigraphy.ResultsMean (±SD) 123I uptake increased from 46.3 (±22.2) % (range, 11.1–80.1) at 3 h, to 66.5 (±15.2) % (range, 40.0–86.1) at 24 h (p < 0.01). CT values ranged from 34.5 to 98.7 HU [mean: 67.8 (±18.6)], while the iodine concentrations calculated with DECT ranged from 0.0 to 1.3 mg/mL [mean: 0.5 (±0.4)]. A moderate positive correlation between CT values and the calculated iodine concentrations in the thyroid gland was seen (R = 0.429, p < 0.05). A significant negative correlation between 123I uptake at 3 h and iodine concentration by DECT were seen (R = −0.680, p < 0.05), although no correlation was observed between 123I uptake at 3 h and CT values (p = 0.087). No correlation was observed between 123I uptake at 24 h and CT values (p = 0.153) or that between 123I uptake at 24 h and iodine concentration by DECT (p = 0.073).ConclusionThe negative correlation of 123I uptake at 3 h with iodine concentration evaluated by DECT was better than that observed with simple CT value. DECT may have a potential role in the evaluation of iodine turnover in hyperthyroid patients.
Highlights
Thyroid function in patients with Grave’s disease is usually evaluated by thyroid scintigraphy with radioactive iodine
These findings suggest that measurement of iodine concentration in the thyroid glands may be useful for the evaluation of iodine turnover, which is a key element of the metabolic pathway of thyroid hormone
There was no correlation between 123I uptake at 3 h and Computed tomography (CT) values (p = 0.087; Fig. 5a), while a significant negative correlation between 123I uptakes at 3 h and iodine concentration assessed with dual-energy computed tomography (DECT) was observed (R = −0.680, p < 0.05; Fig. 5b)
Summary
Thyroid function in patients with Grave’s disease is usually evaluated by thyroid scintigraphy with radioactive iodine. Nygaard et al reported a 50% decrease in 131I uptake 1 week after intravenous injection of 100 mL of iodine contrast agent, which suggests that iodine storage in the thyroid gland would be much affected by its uptake of radioactive iodine [6, 7]. These findings suggest that measurement of iodine concentration in the thyroid glands may be useful for the evaluation of iodine turnover, which is a key element of the metabolic pathway of thyroid hormone
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