Retrospective Study of Tc-99m Thyroid Scan in Patients with Graves' Disease: Is There Significant Difference in Lobar Activity?

PURPOSE: Graves' disease (GD) is the most common cause of hyperthyroidism. It was reported that the right thyroid lobe is generally larger, and it is more likely to be affected by thyroid disorders. The aim of the current study is to verify preferential affection of one of the thyroid lobes and incidence of higher activity of either thyroid lobe in patients with GD through analysis of quantitative data of Tc-99m thyroid scan and possible relation of different thyroid lobar activity to gender, age, and total thyroid uptake (TTU) level. MATERIALS AND METHODS: Retrospective analysis of quantitative data of Tc-99m thyroid scan in patients with GD was done. Total and lobar thyroid uptake levels were analyzed and correlated with age, gender, and TTU. RESULTS: GD was reported in 222 patients, representing 76.6% of those with hyperthyroidism, women represent 70.3% of patients. The right thyroid lobe uptake (RLU) figures were significantly higher compared to the left in the whole group as well as in women and in young patients (<40 years). This significance was lost in men and in old patients. Equal lobar uptake was found in 11 patients. 138 patients (62.2%) had higher RLU, while the remaining 73 patients (32.8%) had higher left thyroid lobe uptake, with statistically significant difference. This significant difference was found in women and in young patients and was absent in men and old patients. There is an increase in the incidence of patients with higher RLU in association with an increase in TTU. All women with TTU >30% had higher RLU figures. CONCLUSION: There is significant preferential thyroid lobar affection in favor of the right thyroid lobe in patients with GD, with significantly higher RLU figures and significantly more incidence of patients with higher right lobar activity. This significance is maintained in women and in young patients and lost in men and old patients. The incidence of higher right thyroid lobe activity also increases in association with increase in TTU. Our results emphasize the value of Tc99m thyroid scan in patients with GD, especially when surgery is the treatment of choice, helping to tailor suitable surgical procedure for each individual patient.

Measurement of cumulative radiation exposure to children and adolescents in contact with outpatients treated with low dose radioactive iodine (131I).

BACKGROUND: Radiation exposure from patients treated with radioactive iodine (131I) represents a radiation hazard to children and adolescents, representing the most vulnerable group of household contacts. Our aim was to calculate the cumulative radiation exposure (CRE) figures to children and adolescents sharing the same home with outpatients treated with low-dose 131I. The secondary aim was to study the demographic and educational factors that may significantly affect radiation exposure to them. RESULTS: The whole number of household contacts less than 18 years was 99, out of them 49 ≤ 12 years. CRE level to children and adolescents ranged from 79 to 934 uSv. The mean, median, and 75th percentile figures were 284 ± 178 uSv, 215 uSv, and 334 uSv, respectively. The compliance of this group of contacts to radiation exposure constraint (1 mSv) was 100%. All CRE values were below this figure with 75% of them below half of this constraint. Thirteen adolescents from 12 to 18 years and 17 mothers of 23 household contacts ≤ 12 years got radiation safety instructions (RSI) directly from a radiation safety officer (RSO). This group had a significantly lower mean CRE value (184 ± 93 uSv) compared to those who got RSI from the patient or from other family members (298 ± 185 uSv) with a significant p value. CONCLUSION: The compliance of adolescents and children to the 1-mSv radiation exposure constraint is 100%. It is advised for adolescents and mothers of children in contact with 131I-treated patients to get direct RSI from the RSO, which is the only factor associated with significantly lower radiation exposure figures.

Impact of histopathology of non-neoplastic thyroid tissue on ablation outcome in patients with papillary thyroid cancer.

OBJECTIVE: To assess the impact of histopathology of non-neoplastic thyroid tissue on ablation outcome in patients with papillary thyroid cancer (PTC). METHODS: The study included 124 patients referred for I-131 ablation therapy after total thyroidectomy for unifocal nonmetastatic PTC. All patients received 100 mCi of I-131 ablation dose. Follow-up whole body scan (WBS) and estimation of serum thyroglobulin level were carried out 6-9 months after ablation therapy and results were divided into complete or incomplete ablation. RESULTS: Incomplete ablation was found in 66.6% (12 of 18), 64% (16 of 25), 39.1% (nine of 23), 30% (six of 20), 33% (six of 18), and 20% (four of 20) in patients with PTC in a background of Hashimoto's thyroiditis, lymphocytic thyroiditis, colloid nodular goiter, nodular hyperplasia, multinodular goiter, and normal thyroid tissue, respectively. Patients with Hashimoto's thyroiditis and lymphocytic thyroiditis had statistically significant higher failure rate to achieve complete ablation compared with other groups. This significant difference was lacking between different nonautoimmune histopathologies and normal thyroid tissue. For patients with thyroid disorders of autoimmune origin (Hashimoto's thyroiditis and lymphocytic thyroiditis), incomplete ablation was found in 65.1% (28 of 43) versus 34.4% (21 of 61) for all other nonautoimmune histopathologies collectively; the difference was statistically significant. CONCLUSION: Histopathology of non-neoplastic thyroid tissue has a significant impact on ablation outcome in patients with PTC. Patients with a histopathology of non-neoplastic thyroid tissue of autoimmune origin have a significantly lower incidence of successful complete ablation after a single I-131 ablative dose (100 mCi) compared with those with nonautoimmune histopathology or with normal thyroid tissue.