• Nuclear Medicine and Molecular Imaging
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• v.43 no.4
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• pp.259-279
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• 2009

Radioiodine ablation therapy has been considered to be a standard treatment for patient with differentiated thyroid cancer after total thyroidectomy. Patients may need to be hospitalized to reduce radiation exposure of other people and relatives from radioactive patients receiving radioiodine therapy. Medical staffs, nursing staffs and technologists sometimes hesitate to contact patients in radioiodine therapy ward. The purpose of this paper is to introduce radiation dosimetry, estimate radiation dose from patients and emphasize the safety of radiation exposure from patients treated with high dose radioiodine in therapy ward. The major component of radiation dose from patient is external exposure. However external radiation dose from these patients treated with typical therapeutic dose of 4 to 8 GBq have a very low risk of cancer induction compared with other various risks occurring in daily life. The typical annual radiation dose without shielding received by patient is estimated to be 5 to 10 mSv, which is comparable with 100 to 200 times effective dose received by chest PA examination. Therefore, when we should keep in mind the general principle of radiation protection, the risks of radiation exposure from patients are low and the medical personnel are considered to be safe from radiation exposure.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.6
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• pp.2523-2527
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• 2014

Background: Serum thyroglobulin detection plays an essential role during the follow-up of thyroid cancer patients treated with total/near total thyroidectomy and radioiodine ablation. The aim of this retrospective study was to evaluate the relationship between stimulated serum thyroglobulin (Tg) level at the time of high dose $^{131}I$ ablation and risk of recurrence, using a three-level classification in patients with differentiated thyroid cancer (DTC) according to the ATA guidelines. Also we investigated the relationship between postoperative stimulated Tg at the time of ablation and DxWBS results at 8-10 months thereafter. Materials and Methods: Patients with radioiodine accumulation were regarded as scan positive (scan+). If there was no relevant pathological radioiodine accumulation or minimal local accumulation in the thyroid bed region, this were regarded as scan negative (scan-) at the time of DxWBS. We classified patients in 3 groups as low, intermediate and high risk group for assessment of risk of recurrence according to the revised ATA guidelines. Also, we divided patients into 3 groups based on the stimulated serum Tg levels at the time of $^{131}I$ ablation therapy. Groups 1-3 consisted of patients who had Tg levels of ${\leq}2ng/ml$, 2-10 ng/ml, and ${\geq}10ng/ml$, respectively. Results: A total of 221 consecutive patients were included. In the high risk group according to the ATA guideline, while 45.5% of demonstrated Scan(+) Tg(+), 27.3% of patients demonstrated Scan(-) Tg(-); in the intermediate group, the figures were 2.3% and 90.0% while in the low risk group, they were 0.6% and 96.4%. In 9 of 11 patients with metastases (81.8%), stimulated serum Tg level at the time of radioiodine ablation therapy was over 10, however in 1 patient (9.1%) it was <2ng/mL and in one patient it was 2-10ng/mL (p=0.005). Aggressive subtypes of DTC were found in 8 of 221 patients and serum Tg levels were ${\leq}2ng/ml$ in 4 of these 8. Conclusions: We conclude that TSH-stimulated serum thyroglobulin level at the time of ablation may not determine risk of recurrence. Therefore, DxWBS should be performed at 8-12 months after ablation therapy.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.2
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• pp.132-140
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• 2006

Well-differentiated thyroid cancer is the most common endocrine malignancy with an increasing incidence. Most patients with well-differentiated thyroid caner have a favorable prognosis with high survival rate. While surgery and radioiodine therapy is sufficient treatment for the majority of patients with differentiated thyroid cancer, a minority of these patients experiences progressive, life-threatening growth and metastatic spread of the disease. Because there is no prospective controlled study to evaluate the differences of management of thyroid cancer, it is hard to choose the best treatment option. And there are still lots of controversies about the management of this disease, such as surgical extent, proper use of radioiodine for remnant ablation and therapy, use of rhTSH instead of withdrawal of thyroid hormone, long-term follow-up strategy, thyroglobulin as a tumor marker, etc. In this review, recent data related to these conflicting issues and recent advances in diagnosis, radioiodine therapy and long-term monitoring of well-differentiated thyroid cancer are summarized.

• The Korean Journal of Nuclear Medicine
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• v.36 no.1
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• pp.87-89
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• 2002

A 30 year-old female patient with papillary thyroid carcinoma received her fifth radioiodine ablation therapy after the subtotal thyroidectomy. The scan, which was peformed one week after the last therapy, revealed residual uptake in the thyroid bed and uptake in the anterior mediastinum suggesting metastasis. However, further evaluation of the thorax with chest CT and camera-based FDG PET confirmed normal thymus without metastatic focus. Occasionally thymus remains intact in adult and has avidity for I-131 and FDG. Therefore, normal thymus (instead of metastasis) should be considered in patients with well differentiated thyroid carcinoma and anterior mediastinal radioiodine uptake.

• The Korean Journal of Nuclear Medicine
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• v.34 no.1
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• pp.22-29
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• 2000

Purpose: We compared the first postoperative diagnostic and post-therapy scans of patients who received therapeutic doses of I-131, to investigate the difference in clinical outcomes between patients with concordant findings of diagnostic and post-therapy scans and patients with discrepant (more lesions in post-therapy scan) findings. Materials and Methods: The first postoperative diagnostic and post-therapy radioiodine scans of one hundred forty three patients with well differentiated thyroid carcinoma were reviewed. Diagnostic scans were obtained following ingestion of 185 MBq of I-131 and post-therapy scans were obtained after therapeutic dose of $3.7{\sim}9.3$ GBq of I-131. Successful ablation was defined as no radioiodine uptake on diagnostic radioiodine scan and normal range of serum thyroglobulin level (<10 ng/ml) during serum TSH elevation. Results: Discrepant scan findings were noted in 25 (17.5%) patients. Twenty-two patients (15.4%) showed more lesions in post-therapy scan and 3 patients (2.1%) showed stunning effect. Nine (64.3%) of 14 patients with distant metastasis revealed metastatic lesion(s) only on post-therapy scan. Stunning effect was considered as sublethal damage in 1 patient and treatment by a diagnostic dose in 2 patients. Ablation was achieved in 52.4% (75/143) of all patients. Ablation rate and mean cumulative radioiodine dose were not different statistically between concordant and discrepant groups. Conclusion: There were 17.5% difference between diagnostic and post-therapy scan findings when using 185 MBq of I-131 as a diagnostic dose. However, 64.3% of distant metastases were revealed only on post-therapy scan. Ablation rate and mean cumulative radioiodine dose were not different statistically between concordant and discrepant groups. The stunning effect was considered as not only sublethal damage but also treatment by a small diagnostic dose of radioiodine.

• The Korean Journal of Nuclear Medicine
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• v.34 no.4
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• pp.265-275
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• 2000

The thyroid gland is an interesting endocrine organ where a spectrum of tumors with different behavior arise. At one end of spectrum there is differentiated thyroid carcinoma (DTC) with excellent prognosis, whereas at the other end of the spectrum is anaplastic thyroid cancer which has universally poor outcome. Radioiodine (I-131) therapy has been in use for the treatment of thyroid diseases since 1946. It was introduced by Seidlin et al. 1) Although the use of I-131 has been vouge for a long time, its use in therapy for well differentiated thyroid cancer is still controversial 2). This is because, thyroid cancers (TC) are generally slow growing tumors, with low mortality and normal spans of survival. To record recurrence and mortality, long term follow up studies over a period of two to three decades are needed to establish definite conclusions on the acceptable mode of treatment The incidence of the disease being very low a large number of cases needed to establish a meaningful statistical data is lacking as most published reports feat with small series. Here again in the problem encountered are the differing protocols for treatment with I-131, the indications for treatment which may include or exclude ablation of residual thyroid tissue, cervical nodal and distal metastases. The dosage of I-131 used for ablation of residual thyroid tissue and metastatic disease also vary. The most reliable conclusion regarding I-131 treatment are obtained from studies reported on a large series of patients followed over a period of 2 decades or more from a single institute with a more or less unchanged protocol of management.

• Journal of Medicine and Life Science
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• v.19 no.3
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• pp.95-102
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• 2022

This retrospective study aimed to investigate whether there was a difference in the success rate of removal of residual thyroid tissue in patients with the same cutoff serum thyroglobulin (Tg) value-measured 2 weeks after thyroid hormone withdrawal (THW)-for different radioactive iodine (RAI) activities. We identified 132 patients with papillary thyroid cancer who were treated with total thyroidectomy and RAI therapy to evaluate the efficacy of three radioactivities of I-131: 1,110, 3,700, and 5,550 MBq. Serum Tg testing was performed 1 week before RAI treatment and 2 weeks after THW (pre-Tg); the cutoff pre-Tg level was below 10 ng/mL. Stimulated Tg levels were measured on the day of I-131 administration (off-Tg). After 6 months of treatment, we compared the groups for complete ablation, defined as no uptake on a diagnostic I-131 scan, stimulated Tg level of <1.0 ng/mL, and Tg antibody level of <100 ng/mL. Ninety-five patients (72.0%) achieved complete ablation, with 57.1% (8/14), 78.2% (68/87), and 61.3% (19/31) in the 1,110 MBq, 3,700 MBq, and 5,550 MBq groups, respectively. There was no significant difference in the complete ablation rates between the three groups. In the multivariate analysis, the off-Tg level was a significant predictor of complete ablation. RAI therapy with low radioactivity (1,110 MBq) seemed sufficient for ablation in patients with papillary thyroid cancer with a pre-Tg level below 10 ng/mL. The off-Tg level is a promising and useful predictor of complete ablation after initial RAI therapy.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.6
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• pp.322-326
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• 2006

A low iodine diet (LID) for $1{\sim}2$ weeks is recommended for patients who undergoing radioiodine remnant ablation. However, the LID educations for patients are different among centers because there is no concrete recommendation for protocol of LID. In this investigation, we compared two representative types of LID protocols performed in several centers in Korea using urine iodine to creatinine ratio (urine I/Cr). Methods: From 2006, April to June, patients referred to our center for radioiodine remnant ablation of thyroid cancer from several local hospitals which had different LID protocols were included. We divided into two groups, stringent LID for 1week and less stringent LID for 2 weeks, then measured their urine I/Cr ratio with spot urine when patients were admitted to the hospital. Results: Total 27 patients were included in this investigation (M:F=1:26; 13 in one-week stringent LID; 14 in two-week less stringent LID. Average of urine I/Cr ratio was $127.87{\pm}78.52{\mu}g/g$ in stringent LID for 1 week, and $289.75{\pm}188.24{\mu}g/g$ in less stringent LID for 2 weeks. It was significantly lower in stringent LID for 1 week group (p=0.008). The number of patients whose urine I/Cr ratios were below $100{\mu}g/g$ was 6 of 13 in stringent LID for 1 week group, and 3 of 14 in less stringent LID for 2 weeks group. Conclusion: Stringent LID for 1 week resulted in better urinary I/Cr ratio in our investigation compared with the other protocol. However it still resulted in plenty of inadequate range of I/Cr ratio, so more stringent protocol such as stringent LID for 2 weeks is expected more desirable.

• Journal of Yeungnam Medical Science
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• v.32 no.2
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• pp.138-142
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• 2015

L-thyroxine (LT4) withdrawal prior to radioactive iodine (RAI) ablation therapy is a commonly used method for successful treatment of patients with papillary thyroid cancer (PTC). However, a prolonged period of hypothyroidism induced by LT4 withdrawal is sometimes associated with impaired quality of life and cardiopulmonary dysfunction in PTC patients. Furthermore, LT4 withdrawal may have a trophic effect on residual cancer by means of increased thyrotropin. We report on 2 cases of metastatic PTC patients with malignant pleural effusion (MPE) whose disease showed rapid worsening after LT4 withdrawal and RAI therapy. The first case is a 65-year-old woman who had PTC with multiple distant metastases and MPE. During LT4 withdrawal for RAI therapy, MPE showed rapid worsening, and the patient required repetitive therapeutic thoracentesis. The second case is a 49-year-old woman with PTC who underwent 3 additional operations for cancer recurrence in the neck lymph nodes and 6 times of RAI treatments. While preparing for the $7^{th}$ RAI treatment by withdrawing LT4, she developed MPE which became progressively aggravated after RAI therapy. Both patients experienced increased pleural effusion during the LT4 withdrawal period and a rise in the thyroglobulin level was observed after RAI therapy. MPE was not controlled with therapeutic thoracentesis and pleurodesis. Eventually, both patients died of rapid disease progression after RAI therapy. In summary, LT4 withdrawal may have an adverse effect on metastatic PTC patients, particularly those with MPE.

• Korean Journal of Head & Neck Oncology
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• v.15 no.1
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• pp.46-51
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• 1999

Background: Total thyroidectomy and postoperative radiodiodine ablation therapy in differentiated thyroid carcinomas enhance the reliability of serum thyroglobulin(Tg) levels and radioiodine scan in detecting recurrence or distant metastasis. There have been, however, some limitations in using these methods under certain conditions. Recently, several reports have indicated that thyroid peroxidase(TPO) could be used as an alternative tumor marker. We aimed to estimate the significance of serum TPO levels in differentiated thyroid carcinoma. Materials and Methods: Forty-eight patients who had undergone total thyroidectomy due to papillary thyroid carcinomas and who had been followed-up for at least 3 years were classified into two groups: 27 patients without any evidence of recurrence in group 1; and 20 patients with recurrence or distant metastasis in group 2. All patients were examined by radioiodine scans. Serum Tg, TSH, antithyroglobulin antibody, and TPO were measured and the relationships were statistically analyzed. The sensitivity and specificity of $^{131}I$ scan, serum Tg, and serum TPO were evaluated. Results: Serum Tg levels were $3.81{\pm}5.16ng/mL$ in group 1 and $147.02{\pm}193.75ng/mL$ in group 2. Only 2 patients in group 1 showed Tg levels exceeding 10ng/mL. In contrast, 4 patients in group 2 were under 10ng/mL. Serum antithyroglobulin antibody and TSH levels showed no statistical difference between the two groups. In group 1, 16 patients showed negative serum TPO results, and 4 patients in group 2 showed negative results. There was no correlation among serum Tg levels, antithyroglobulin antibody titers, and serum TPO levels in each group. In group 2, 4 patients with negative serum Tg levels showed positive TPO results and positive whole body scans. Two cases with false negative $^{131}I$ scans showed positive serum TPO and Tg results. In 4 cases showing false negative serum TPO levels, serum Tg levels and $^{131}I$ scans were positive. Conclusion: Serum Tg levels, radioiodine scans, and serum TPO levels can be clinically used as complementary methods in the diagnosis of recurrent or metastatic thyroid carcinomas. Serum TPO levels may be helpful when other methods fail to detect recurrences or distant metastasis in highly suspected patients.