Clinical Studies on Thyroid CT Number in Chronic Thyroiditis.

Abstract

Abstract. The purpose of the present study is to investigate by a computed tomography (CT) thyroid CT number (Hounsfield units; H.U.) in chronic thyroiditis (CH).The correlation of the CT value with the concentration of KI solution in the test tube of thyroid phantom for thyroid scintigram was linear. No significant correlation between thyroid CT number and the urinary iodine concentration was also observed in 36 patients with CH. A mean thyroid CT number (± SD) of 81 ± 24 H.U. in 155 patients with CH was significantly (P<0.001) lower than 125 ± 18 H.U. in 95 normal subjects. The patients with CH could be arbitrarily divided into 3 groups according to the decrease in their thyroid CT number: normal (N) group (? 88 H.U.), moderately decreased (MD) group (70-87 H.U.) and the greately decreased (GD) group (<70 H.U.). There was a significant difference in the thyroid volume among 21.2±9.1 cm3 in the N group, 32.2± 18.1 in the MD group (P<0.05 vs. N group) and 43.6±23.3 in the GD group (P<0.01 vs. N and MD group). The mean serum TSH concentration of 38.95 ± 54.61 µU /ml in the SD group was significantly (P<0.01) higher than either 4.11 ± 3.64 in the MD group or 2.00± 1.43 in the N group. The serum TSH level in the MD group differed significantly (P<0.05) from that of the N group.Hypothyroidism characterized by low serum FT 4 (<0.8 ng/dl) and very high serum TSH was observed in none in the N group, in 2 (7.1%) of 28 cases in the MD group and in 16 (33.3%) of 48 cases in the GD group. And latent hypothyroidism characterized by an increase in serum TSH levels (? 5 µU / ml) and normal concentrations of thyroid hormones was found in 2 (5.1%) of 39 cases in the N group, 5 (17.9%) in the MD group and 16 (33.3%) of the GD group. There was a significant (P<0.005) difference in multiple chi-square analysis in the comparison between the GD group and the N group or MD group. The frequency of higher titers of antimicrosomal Ab and antithyroglobulin Ab seemed to be correlated with the amount of decrease in the thyroid CT number. In conclusion, there was a significant correlation between the thyroid CT number and the severity of chronic thyroiditis.

Computed Tomography Density Change in the Thyroid Gland Before and After Radiation Therapy

“…For example, CT densities repeatedly decrease when TSH concentrations are >3.0 mIU/L (5). In patients with normal serum TSH concentrations, mean CT densities of the thyroid gland on non-contrast CT images reportedly range from 97.4 to 122 HU (4,5). In our patients, the mean CT density of the thyroid gland before radiation therapy was 104.9 HU, which is comparable with previously reported densities in patients with normal thyroid function.…”

“…In this study, correlation of mean CT densities and thyroid function showed that a significantly greater proportion of patients with low than with high thyroid attenuation had hypothyroidism. Because iodine concentrations are controlled by a feedback loop involving serum TSH, densities of the thyroid gland on non-contrast CT images reportedly correlate with serum TSH concentrations (4,5). For example, CT densities repeatedly decrease when TSH concentrations are >3.0 mIU/L (5).…”

“…Hypothyroidism is a well-known adverse effect of radiation therapy for head and neck cancer (1)(2)(3). It has also been established that the computed tomography (CT) density of the thyroid gland decreases in hypothyroidism caused by chronic thyroiditis and other conditions (4,5). We therefore postulated that the onset of radiation therapy-induced hypothyroidism could be predicted on the basis of changes in CT densities of the thyroid gland before and after radiation therapy.…”

Is 18F-FDG PET/CT Useful for Distinguishing Between Primary Thyroid Lymphoma and Chronic Thyroiditis?

“…22,23,25,26 Our data for these 2 groups revealed values of 46.1 and 62.1, respectively, consistent with the aforementioned reports. 6,22 On the other hand, mainly tumor attenuation is seen in cases of PTL, regardless of the iodine content of the thyroid, because most PTL cases show dense proliferation of lymphoma cells and sheet-like effacement of the thyroid parenchyma, and microscopic examination reveals few normal thyroid follicles (Fig. The decreased attenuation in chronic thyroiditis is thought to reflect the decreased iodine density in the thyroid gland caused by diffuse infiltration of the gland by lymphocytes and lymphoid follicles with reactive germinal centers.…”

“…22,23 On the other hand, the CT density of the thyroid gland has been reported for small number of PTL patients 24 and is not well known. According to previous reports, patients with chronic thyroiditis exhibit decreased CT density of the thyroid gland as compared to healthy subjects.…”