MBq Of 131I Research Articles

Correlation between the thyroid computed tomography value and thyroid function in hyperthyroidism: a retrospective study

ObjectiveRadioiodine (I-131) therapy for hyperthyroidism is a well-established and safe treatment option. This study aimed to investigate the relationship between the computed tomography (CT) value and the function and volume of the thyroid gland by identifying the factors that induce changes in the CT value of patients with hyperthyroidism.MethodsThis retrospective study evaluated 38 patients with Graves’ disease and 10 patients with Plummer disease. To obtain the mean CT value and volume of the thyroid gland, the entire thyroid gland was set as the region of interest. A test dose of 3.7 MBq I-131 was administered before initiating I-131 therapy, and the radioiodine uptake (RIU) rate was assessed after 3, 24, 96, and 168 h. An approximate curve was plotted based on the RIU values obtained, and the effective half-life (EHL) was calculated. The correlation between the mean CT value and the volume of the thyroid gland, 24-h RIU, EHL, and the free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), and TSH receptor antibody (TRAb) levels was evaluated.ResultsThe CT value exhibited a significant positive correlation with EHL in patients with Graves’ disease (r = 0.62, p < 0.0001) as well as patients with Plummer disease (r = 0.74, p < 0.05). However, it did not display any correlation with the remaining parameters.ConclusionThe CT value is significantly correlated with EHL, suggesting that it reflects thyroid function and is mainly related to the factors associated with iodine discharge.

The Value of Pre-Ablative I-131 Scan for Clinical Management in Patients With Differentiated Thyroid Carcinoma.

BackgroundA diagnostic I-131 (Dx) scan is used to detect a thyroid remnant or metastases before treatment of differentiated thyroid cancer (DTC) with I-131. The aim of this study is to specify in which patients with DTC a Dx scan could have an additional value, by studying the effect of the Dx scan on clinical management.MethodsPatients with DTC, treated with I-131 after thyroidectomy were included in this retrospective cohort study. Twenty-four hours after administration of 37 MBq I-131 a whole body Dx scan and an uptake measurement at the original thyroid bed were performed. Outcomes of the Dx scan and the subsequent changes in clinical management, defined as additional surgery or adjustment of I-131 activity, were reported. Risk factors for a change in clinical management were identified with a binary logistic regression.ResultsIn 11 (4.2%) patients clinical management was changed, including additional surgery (n=5), lowering I-131 activity (n=5) or both (n=1). Risk factors for a change in clinical management were previous neck surgery (OR 5.9, 95% CI: 1.4-24.5), surgery in a non-tertiary center (OR 13.4, 95% CI: 2.8 – 63.8), TSH <53.4 mU/L (OR 19.64, 95% CI: 4.94-78.13), thyroglobulin ≥50.0 ng/L (OR 7.4, 95% CI: 1.6-34.9) and free T4 ≥4.75 pmol/L (OR 156.8, 95% CI: 128.4-864.2)ConclusionThe Dx scan can potentially change clinical management before treatment with I-131, but the yield is low. A Dx-scan should only be considered for patients with a high pre-scan risk of a change in management, based on patient history and prior center-based surgical outcomes.

3D printing of fillable individual thyroid replicas based on nuclear medicine DICOM data used as phantoms for gamma probe calibration.

To proof the feasibility of manufacturing patient-indivdual (anthropomorphic) thyroid replicas from I-124 PET DICOM datasets by means of 3D printing. A possible field of application is the use of those phantoms for the calibration of gamma probes. After editing of the DICOM datasets using several software types and transferring into a dedicated stereolithography format, 10 fillable thyroid replicas (35-200 mL) made of polylactide acid were manufactured via 3D printing. All replicas were filled with a water-solution containing 3.5 MBq I-131 and applied to a standard neck phantom. Calibration factor measurements were carried out using a clinical gamma probe. Measurements were performed with three different tilts: + 15°, 0° and -15°. The influence of the replicas' volume and the tilt was investigated. Manufacturing of the replicas was successful in all cases. The time required for data processing was 13 ± 2 (median: 12, range: 9-25) min and 4-11 h for 3D printing (size-dependent). The printing process could be done overnight. Measured mean calibration factor for straight gamma probe positioning (0° tilt) was 31 965 ± 3360 (33 893, 25 470-34 253) cpm/MBq. A tilt of -15° resulted in lower calibration factors (-7.7 %), whereas a tilt of + 15° led to higher values (+ 9.5 %); p = 0.001. The calibration factors were highly inversely proportional correlated to the volume of the replicas (r = -0.91, p < 0.001). 3D printing of patient-individual (anthropomorphic) fillable thyroid replicas was feasable for a large range of volumes. The study demonstrates the influence of the volume as well as the tilt of the measured object for calibration factor measurements with gamma probes.

Finding the best effective way of treatment for rapid I-131 turnover Graves' disease patients: A randomized clinical trial.

Background:Rapid I-131 turnover Graves’ disease patients have low cure rate. We aimed to compare cure percentage at 12 months among 3 treatment doses of I-131 with or without lithium carbonate (LiCO3) in rapid turnover Graves’ disease patients.Methods:Sixty Graves’ disease patients referred for radioactive iodine treatment were randomised into three arms of treatment: Group A, 3.7 MBq I-131/g thyroid plus 600 mg/day LiCO3, Group B, 5.55 MBq I-131/g plus 600 mg/day LiCO3, and Group C, 7.4 MBq I-131/g without LiCO3. Data were collected at baseline, 3, 6, 9, and 12 months. The primary endpoint were cure rates (percentage of euthyroid or hypothyroid) at 12 months. Pairwise comparisons were made across 3 groups using an equality of proportions test. The secondary endpoint, the odds of cure over the total follow-up for group B and C versus group A, was analyzed using generalized estimating equation (GEE). Side effects of I-131 and LiCO3 treatment were evaluated at 1 to 2 weeks after treatment.Results:The cure rate at 12 months was 45% (9/20) for group A, 60% (12/20) for group B and 80% (16/20) for group C. The mean difference in proportion cured at 12 months between group C and group A was 35 (7.0 to 66.8)%; P-value = .02. There was a statistically significant difference between cure rates over all follow-up of group C and A after adjustment for sex (adjusted OR = 3.09; 95%CI = 1.32–7.20; P-value = .009), but no significant difference was found between group B and A or C and B in the primary and/or secondary efficacy endpoints. Side effects from the treatment were found in 12% (7/60); 2 in group A, 4 in group B, and 1 in group C. Four of these were likely due to LiCO3 side effects.Conclusions:Treatment of rapid turnover Graves’ disease patients with high dose I-131 (7.4 MBq/g) provides significantly higher cure rates at 12 months, and 3 times odds of cure than 3.7 MBq/g I-131 plus LiCO3 with lesser side effects. We thus recommend 7.4 MBq I-131/g for treatment in these patients.

The assessment of radio-adaptive response in graves' hyperthyroidism patients following radioactive iodine uptake.

Low doses of radiation affect the response of cells to higher doses; this phenomenon is called radio-adaptive response, which leads to increased resistance to subsequent higher doses. We have investigated the adaptive response using 0.37 MBq priming dose of I-131 followed by 296–444 MBq challenging dose in peripheral human lymphocyte cells. The study was performed on 42 patients with Graves' disease and 29 healthy adult persons as a control group. The patients were divided into two groups. In the first group, patients were referred for radioactive iodine therapy with a specific dose, and iodine was given to them on the day of referral. In the second group, patients were referred for radioactive iodine uptake and radioactive iodine therapy, and iodine uptake was initially performed, then 24 h later, iodine therapy was done. In both groups, 1 month after treatment, blood samples were taken to cytokinesis-block micronucleus (MN) assay. The number of MN in binuclear lymphocyte cells was counted as an end point test. The mean frequency of MN in first, second, and control groups was 75.86 ± 12.68, 71.45 ± 12.56, and 20.06 ± 7.30, respectively. Our results showed that the frequency of total chromosome aberration in both radiation groups was higher than controls. However, in the first group was higher than another group, but their difference was not statistically significant. According to the results, we cannot approve the hypothesis that 0.37 MBq I-131 administration before iodine therapy could induce a radio-adaptive response in lymphocytes of Graves' patients.

Outcome of radioiodine therapy in patients with papillary thyroid carcinoma concurrent with Hashimoto′s thyroiditis

Objective To evaluate the impact of low-dose 131I therapy and high-dose 131I therapy on the clinical outcome in PTC patients coexisting with Hashimoto′s thyroiditis (HT). Methods A total of 140 non-distant metastatic PTC patients (16 males, 124 females, age range: 16-66 years) from July 2010 to December 2014 were enrolled in this retrospective study. Patients concurrent with HT (n=84, group A) were divided into low-dose group (1 110 MBq, n=56, group A1) and high-dose group (5 550 MBq, n=28, group A2) according to 131I ablation dose. Patients without HT (n=56) were enrolled as control group (group B), and received 1 110 MBq of 131I. The thyroid remnant ablation outcome was evaluated according to 131I diagnostic whole-body scan (Dx-WBS), neck ultrasonography (US), serum Tg and TgAb level 6-8 months after 131I ablation therapy. The successful ablation rates were compared by χ2 test. Kruskal-Wallis rank sum test was also used. Results There were no significant differences among the 3 groups in terms of both clinicopathological features and postoperative remnant thyroid (H: 0.203-2.944, χ2: 0.271-0.970, all P>0.05). When negative Dx-WBS and US were deemed as successful ablation criterion, complete ablation rate was found significantly more in group B (94.6%, 53/56) than that in group A1 (82.1%, 46/56; χ2=4.264, P 0.05). When combining negative sTg (sTg 0.05), and no difference was observed between group A2 (12/15) and group A1 (χ2=1.320, P>0.05). Conclusion Non-distant metastatic PTC patients coexisting with HT has undesirable 131I ablation outcome compared with those without HT, increasing 131I dose is unhelpful to enhance efficiency of remnant ablation for PTC patients with HT. Key words: Thyroid neoplasms; Hashimoto disease; Radiotherapy; Iodine radioisotopes; Treatment outcome

Radioiodine therapy activity 550 MBq of I131 in thyrotoxicosis patients

Background. Radioiodine therapy (RIT) is an alternative method to surgical treatment used in the treatment of hyperthyroidism (Graves’ disease or solitary/multinodular toxic goiter (STG/MTG) etiology). However, treatment protocol doesn’t exist. Aim. To evaluate the outcomes of the I131 treatment in hyperthyroidism using the standard dose (550 Mbq), and to explore the factors that influence the outcome of treatment. Methods. We studied 38 patients (35 women and 3 men) with hyperthyroidism. Each patient was carried I131 RIT in a dose of 550 Mbq. Patients were randomized 2 group – patients with Gravesa disease and patients with a solitary/multinodular toxic goiter. Antithyroid drugs withdraw was usually conducted for 7–14 days prior to RIT. Follow-up period ranged from 6 to 8 months, the average was 6.6 ± 0.4 months. Results. Six months after the RIT 23 patients (61%) reached hypothyroidism, 7 patients (18%) was observed euthyroidism, thyrotoxicosis stayed in 8 patients (21%). In patients with Gravesa disease onset hypothyroidism were more likely (75% vs 35.7%, p < 0.001). Thus at STG/MTG achieve euthyrosis percentage was higher (28.6% vs 12.5%). Predictors of a positive outcome of the treatment are: less thyroid size (<30 ml for women, <40 ml for men) and younger age (under 35 years old). Statistical significance in influencing the outcome of treatment by disease duration, level of stimulating antibodies against thyrotropin receptors have not been identified. Conclusions. Fixed activity of 550 MBq I131 has a different efficacy in the treatment of hyperthyroidism in patients with Graves’ disease and STG/MTG. In addition, on treatment results affect patient age and the size of the thyroid gland, which should be considered during planning RIT. In order to improve the effectiveness of radioiodine therapy of hyperthyroidism requires personalization tactics of treatment based on clinical factors, as well as the use of in vivo dosimetry planning when therapeutic activity calculating.

Re-ablation I-131 activity does not predict treatment success in low- and intermediate-risk patients with differentiated thyroid carcinoma.

The aim of this study was to evaluate the efficacy of different radioactive iodine (I-131) activities used for re-ablation, to compare various combinations of treatment activities, and to identify predictors of re-ablation failure in low- and intermediate-risk differentiated thyroid carcinoma (DTC) patients. The study included 128 consecutive low- and intermediate-risk patients with DTC with ablation failure after total thyroidectomy. Patient characteristics, T status, tumor size, lymph node involvement, postoperative remnant size on whole-body scintigraphy, serum thyroglobulin (Tg), thyroid-stimulating hormone (TSH), anti-Tg antibody (TgAb), and Tg/TSH ratio were analyzed as potential predictors of the re-ablation success. Re-ablation was successful in 113 out of 128 patients (88.3%). Mean first I-131 activity was 2868±914MBq (77.5±24.7mCi) and mean second I-131 activity 3004±699MBq (81.2±18.9mCi). There was no association between the first, second, and cumulative activity with re-ablation treatment outcome. Treatment failure was associated with higher Tg levels prior to re-ablation (Tg2) (OR 1.16, 95% CI 1.05-1.29, P=0.003) and N1a status (OR 3.89, 95% CI 1.13-13.41, P=0.032). After excluding patients with positive-to-negative TgAb conversion, Tg2 level of 3.7ng/mL predicted treatment failure with a sensitivity of 75.0%, specificity of 80.5%, and a negative predictive value of 97.1%. Patients with positive-to-negative TgAb conversion had higher failure rates (OR 2.96, 95% CI 0.94-9.29). Re-ablation success was high in all subgroups of patients and I-131 activity did not influence treatment outcome. Tg may serve as a good predictor of re-ablation failure. Patients with positive-to-negative TgAb conversion represent a specific group, in whom Tg level should not be used as a predictive marker of treatment outcome.

Radioiodine ablation with 1,850 MBq in association with rhTSH in patients with differentiated thyroid cancer

The aim of this study was to evaluate the efficacy of post-operative radioiodine ablation with 1,850 MBq after recombinant human thyrotropin (rhTSH) administration in patients with differentiated thyroid carcinoma (DTC). We also aimed to assess the prognostic role of several patient features on the outcome of ablation. We retrospectively analyzed data from a total of 125 patients with DTC who underwent post-operative radioiodine ablation with 1,850 MBq of ¹³¹I after preparation with rhTSH. One injection of 0.9 mg rhTSH was administered on each of two consecutive days; ¹³¹I therapy was delivered 24 h after the last injection, followed by a post-therapy whole-body scan. Successful ablation was assessed 6-12 months later and defined as an rhTSH-stimulated serum thyroglobulin (Tg) level ≤1.0 ng/ml and a normal neck ultrasound. Patients were stratified according to the American Thyroid Association (ATA) Management Guidelines for Differentiated Thyroid Cancer. Successful ablation was achieved in 82.4 % of patients, with an ablation rate of 95.1 % in low-risk patients and 76.2 % in intermediate-risk patients. Analyzing the correlation between ablation outcome and patient characteristics, we found a statistically significant association between failure to ablate and class of risk based on ATA guidelines (p = 0.025) and a stimulated Tg value at ablation of above 5 ng/ml (p < 0.001). The use of 1,850 MBq post-operative radioiodine thyroid remnant ablation in association with rhTSH is effective for low- and intermediate-risk patients. Moreover, in our study, we found a statistical correlation between failure to ablate and class of risk based on ATA guidelines for DTC and a stimulated Tg value at ablation.

The limit of detection in scintigraphic imaging with I-131 in patients with differentiated thyroid carcinoma

Radioiodine scintigraphy influences staging and treatment in patients with differentiated thyroid carcinoma. The limit of detection for fractional uptake in an iodine avid focus in a scintigraphic image was determined from the number of lesion net counts and the count density of the tissue background. The count statistics were used to calculate the diagnostic activity required to elevate the signal from a lesion with a given uptake significantly above a homogeneous background with randomly distributed counts per area. The dependences of the minimal uptake and the minimal size of lesions visible in a scan on several parameters of influence were determined by linking the typical biokinetics observed in iodine avid tissue to the lesion mass and to the absorbed dose received in a radioiodine therapy. The detection limits for fractional uptake in a neck lesion of a typical patient are about 0.001% after therapy with 7000 MBq, 0.01% for activities typically administered in diagnostic assessments (74–185 MBq), and 0.1% after the administration of 10 MBq I-131. Lesions at the limit of detection in a diagnostic scan with biokinetics eligible for radioiodine therapy are small with diameters of a few millimeters. Increasing the diagnostic activity by a factor of 4 reduces the diameter of visible lesions by 25% or about 1 mm. Several other determinants have a comparable or higher influence on the limit of detection than the administered activity; most important are the biokinetics in both blood pool and target tissue and the time of measurement. A generally valid recommendation for the timing of the scan is impossible as the time of the highest probability to detect iodine avid tissue depends on the administered activity as well as on the biokinetics in the lesion and background in the individual patient.

Radioiodine retention on percutaneous endoscopic gastrostomy tubes

An 80-year-old male with recurrent thyroid cancer and a percutaneous endoscopic gastrostomy (PEG) tube in situ was referred for radioiodine therapy and was administered 5510 MBq I-131 sodium iodide intravenously. Sequential whole-body images taken over the subsequent 7 days for dosimetric evaluation revealed an area of persistent high uptake in the abdomen. Delayed imaging with single photon emission CT/CT at 15 days post administration revealed this uptake to be at the junction of the PEG tube with the anatomically normal stomach wall. We hypothesise that the PEG tube became contaminated by radioiodine secreted in the gastric mucosa during therapy and this radioactivity subsequently decayed with an increased effective half-life relative to the stomach, leading to the apparent hot spot.

A retrospective study on the transition of radiation dose rate and iodine distribution in patients with I-131-treated well-differentiated thyroid cancer to improve bed control shorten isolation periods

To evaluate for how long patients should be isolated after I-131 treatment for thyroid cancer according to the guidelines issued by the Japanese Ministry of Welfare. We reviewed 92 therapies performed in 76 patients who were administered I-131 at our hospital from July 2007 to September 2009. Fifty-six patients were given 2220 or 2960 MBq I-131 at the first therapy, and 29 patients underwent 36 repeated therapies using 2960, 3700, 5550 or 7400 MBq I-131. We surveyed radioactivity for a 1 cm dose equivalent rate at 1 m intervals at 30 and 48 h after administration of I-131, obtained planar scintigrams at 48 h, and surveyed radioactivity repeatedly until it fell to under 30 μSv/h. The radioactivity was under 30 μSv/h at 30 h in 51 out of 92 cases (55%). Among the remaining 41 (45%) cases, 27 (29%) and 32 (35%) cases showed decreased radioactivity under 30 μSv/h at 48 and 72 h, respectively, and it remained higher than 30 μSv/h at 72 h in another 9 cases (10%). In 5 (38%) of the 13 cases with bone metastasis, the radioactivity remained over 30 μSv/h after 72 h, and scintigrams showed strong accumulation in bone metastases. Among the 27 cases demonstrating below 30 μSv/h at 48 h, 26 showed radioactivity being below 50 μSv/h at 30 h, while it was above 50 μSv/h at 30 h in all 14 cases which demonstrated above 30 μSv/h at 48 h. We compared the radioactivity levels of 27 cases under 30 μSv/h at 48 h and 14 cases over 30 μSv/h at 48 h using a cutoff value of under 50 μSv/h at 30 h to release patient at 48 h, the positive predictive value and negative predictive value were 100 and 93%, respectively, and radioactivity was found to differ significantly (P < 0.001). To predict external radiation levels at 48 h, it is helpful to consider external radiation levels at 30 h after treatment. Consideration of intracellular uptake in thyroid cancer, especially in cases of bone metastases, digestive tract function, and renal function, is important for predicting isolated period.

Dosimetry prior to I-131-therapy of benign thyroid disease

The activity to be administered in I-131 therapy of benign thyroid disease is determined by the radiation absorbed dose necessary to cure the disease, the target mass, and the residence time of the I-131 in the target volume. Data from 73 patients with complete sets of uptake measurements 2, 6, 24, 48, and 96 (n = 53) or 120 (n = 20) hours after oral administration of 1 MBq I-131 were used to deduce residence times from subsets of 3, 2, or only 1 measurement for each individual. The values were compared to those obtained with the reference method, i.e. a fit of an uptake function based on a 2-compartment model to all 5 measurements, to quantify the errors introduced by the less demanding assessments. Deviations are less than 10% if the 2- compartment uptake function is fitted to only 3 values measured after 6, 24, and 96-120 h. Use of 2, 24, and 96-120 h data results in errors >20% in individual patients. The effective half-lives as determined from 2 measurements after 24 and 96-120 h correlate well with those deduced from the reference method with larger deviations in individuals with slow iodine kinetics and late maximal uptake. Residence times determined from the 24 h uptake, assuming linear increase during the first day, and the effective half-life limited to maximum 8 days underestimate the actual values systematically in patients with long and short half-lives. These errors can be eliminated by a modification of the calculation method resulting in deviations less than 14% in all but one individual for this procedure. The accuracy of methods based on only one retention value increases with the time of measurement after the administration of I-131. While systematic errors up to a factor of two occur if the 24 h uptake is used for the estimate, deviations are less than 18% for measurements after 120 h. The results suggest that only one late uptake assessment warrants residence time estimates with an acceptable error. Given the high inherent uncertainties in the complete dosimetry procedure, additional measurements must be considered only if a high precision of the absorbed dose assessment is required e.g. for clinical trials.

Thyroid Cancer after Chernobyl: Obfuscated Truth

Causes and mechanisms of the registered incidence increase of pediatric thyroid cancer (TC) after the Chernobyl accident, unrelated to the ionizing radiation, were recently reviewed among other topics by Prof. Z. Jaworowski (2010). The main body of evidence (Cardis et al. 2005; Tronko et al. 2006; Davis et al. 2004) in favor of the cause-effect relationship between ionizing radiation and TC among children and adolescents after the Chernobyl accident is based upon the epidemiologic studies (Ron 2009). In the case-control study (Cardis et al. 2005) a retrospective estimation of doses was performed by questioning. The study by Davis et al. (2004) was similar in design. The ‘Chernobyl victim syndrome’ (Bay and Oughton 2005) was a widespread phenomenon: many patients strived for higher dose estimations to support their status as Chernobyl victims, and provided biased information. Cancer patients could have remembered circumstances related to the exposure better than the controls. Iodine supplementation months after the exposure was reported to reduce the cancer risk threefold (Cardis et al. 2005), although radioiodine would have already been absorbed and there would be no blockage in uptake that could have reduced thyroid dose (Boice 2005). Some aspects of the study design by Cardis et al. (2005), favoring an LNT-type dose-response relationship, were criticized by Scott (2006). The dose-response relationship in the recent epidemiologic study by Zablotska et al. (2011) is even stronger at the low dose level: it can be seen in the graph 2 in this paper that the dose-effect curve (P 10 Gy of external radiation (Ron et al. 1995). The decrease of risk at higher doses is explained by the effect of cell killing (UNSCEAR 2006; Boice 2005). However, no leveling of TC risk was found by Shore et al. (1985) at the doses of external radiation up to 10 Gy. In a case-control study following radiotherapy for childhood cancer, it was found that exposures around 60 Gy were associated with a high risk of TC (UNSCEAR 1994). For comparison, in a review of a series of studies in rats, a carcinogenic effect on the thyroid of 11 Gy from acute x-ray exposure was compatible to that from injection of 1.1 MBq of 131I, which would give a dose of about 100 Gy, when significant cell killing might be expected (UNSCEAR 1993). The cell killing concept appears to be inapplicable for the doses around 3 Gy from radioiodine, when thyroid remains gross unchanged, the bulk of follicular epithelium remains viable, preserving capability of mitosis. In other words, the cancer field, i.e. exposed follicular cells as a field for potential carcinogenesis, remains in place. Therefore, it appears probable that both the dose-effect relationship at minimal doses and its disappearance at higher doses in (Zablotska et al. 2011) are caused by biases and other factors rather than by radiation, which would be in agreement with evidence in favor of low (if any) carcinogenicity of 131I, used for diagnostic and therapeutic purposes (Hahn et al. 2001; Dickman et al. 2003; Boice 2005; Holm et al. 1991; Wartofsky 2010; DeGroot 1993). Interestingly, Zablotska et al. (2008) found in individuals, exposed as children or adolescents to ionizing radiation, a significant LNT-type dose-response relationship also for follicular thyroid adenoma, a benign condition, which is different in pathogenesis from papillary carcinoma prevailing among post-Chernobyl pediatric TC. It is worth mentioning here that a cause of the unusually high percentage of papillary carcinoma among TC cases in the screened Chernobyl populations is clear for a pathologist, acquainted with the diagnostic practice of that time: reliable diagnostics of a follicular TC often requires a great number of high-quality histological slides from the capsular area of a nodule, which was usually not done because of technical reasons and insufficient awareness of the minimally invasive follicular TC, absent in Russian-language literature. Paradoxically, if papillary TC was overdiagnosed after the Chernobyl accident (Jargin 2009a), follicular TC probably was under-diagnosed.

Radioprotective Role of Selenium after Single-Dose Radioiodine (131I) Exposure to Red Blood Cells of Rats

The present study elucidated the protective potential of selenium following ¹³¹I-induced alterations in rat blood. Forty rats were segregated into 4 groups. Animals in Group I served as normal controls, Group II animals were injected with a single dose of 3.7 Mbq of ¹³¹I (carrier free), Group III animals were supplemented with selenium (1 ppm), and Group IV animals were given a combined treatment of selenium and ¹³¹I. ¹³¹I treatment of rats showed significant increases in total leukocyte counts (TLCs), lymphocytes, and neutrophils (monocytes and eosinophils were not recorded). These were significantly restored upon supplementation of selenium. Lipid peroxidase (LPO), glutathione peroxidase (GSH-PX), reduced glutathione (GSH), superoxide dismutase (SOD), and δ-aminolevulinic acid dehydratase (δ-ALAD) were found to be enhanced following ¹³¹I treatment. However, the levels of catalase were found to be decreased. Selenium administration to ¹³¹I-treated rats resulted in significant restoration of these enzyme activities. Scanning electron microscope (SEM) studies also revealed various surface deformities in erythrocytes after ¹³¹I treatment, which upon supplementation with selenium were significantly restored. In conclusion, selenium may prove to be an effective radioprotector following ¹³¹I treatment.

Pyelocaliceal Diverticulum as a Rare Pitfall in I-131 Post-Therapy Scanning

A 65-year-old woman with follicular thyroid carcinoma was treated with total thyroidectomy and radioiodine ablative therapy with 3943 MBq (107 mCi) I-131. Whole-body planar scintigraphy revealed an increased radioactivity in the upper pole of the right kidney, suggesting an unusual case of renal metastasis of a follicular thyroid carcinoma. SPECT/CT using a low dose CT protocol was performed as well as ultrasound. Although ultrasound revealed a cyst in the upper pole of the right kidney, the low dose CT was not helpful to differentiate a cyst from a solid renal tumor. Pyelocaliceal diverticulum may be considered as a pitfall in I-131 scintigraphy.

Thyrotropin variations may explain some positive radioiodine therapy scans in patients with negative diagnostic scans

Thyroglobulin (Tg) is a specific marker of residual thyroid cancer or tumor recurrence. In patients with elevated Tg levels and negative diagnostic radioiodine (131I) whole-body scans (dWBS), administration of a therapy dose may reveal foci that were not initially apparent. The aim of this study was to identify factors, other than 131I activity, which might explain why a post-therapy 131I whole-body scan is sometimes positive despite a negative dWBS. We reviewed data on all patients with elevated Tg levels and negative dWBS with 185 MBq 131I off-T4 at followup, who subsequently received an empiric therapy dose of 3700 MBq of 131I. During a 5-yr period, 22 patients met these criteria. 131I therapy could be given immediately after negative dWBS in 9 patients, with an average of 8 extra days of hypothyroidism. In the other 13 patients, therapy was given an average of 8 months later. The therapy scan was negative in 16 patients, while it showed uptake in the thyroid bed in 5 patients and distant metastases in two. In the latter two patients, the TSH level was suboptimal at the time of dWBS (9 and 25 microIU/ml), and had risen to 34 and 70 microIU/ml respectively at the time of therapy. Overall, a positive scan following therapy occurred in 7 patients (6/9 patients treated immediately and 1/13 patients treated in a separate setting; p<0.01). In patients with positive therapy scans, the mean TSH level was 73 microIU/ml at the time of dWBS and 103.5 microIU/ml at the time of therapy (41% increase; p<0.05). In patients with negative therapy scans the mean TSH level was 84 microIU/ml at dWBS and 86 microIU/ml at the time of the therapy scan (2% increase). Our study suggests that interval increase in TSH level with a longer period of stimulation may have contributed to making the whole-body scan positive at the time of therapy. Nowadays, patients with elevated Tg are directly given a therapy dose of 131I. Special care should be taken when preparing patients who have been on suppressive levothyroxine therapy for a long time, in order to avoid misclassifying the tumor as non-functioning.

131I Induced Hematological Alterations in Rat Blood: Protection by Zinc

The present study was planned to determine the potential of zinc in attenuating the toxicity induced by 131I in rat blood. Female wistar rats were segregated into four main groups. Animals in Group I served as normal controls; Group II animals were administered a dose of 3.7 Mbq of 131I (carrier free) intraperitoneally, Group III was supplemented with Zinc in the form of ZnSo4.7H2O (227 mg/l drinking water), and Group IV was given a combined treatment of Zinc as well as 131I, in a similar way as was given to Groups IV and II animals, respectively. The effects of different treatments were studied on various parameters in rat blood including hemoglobin (Hb) levels, % hematocrit, zinc protoporphyrins (ZPP), activities of enzymes which included aminolevulinic acid dehydratase (delta-ALAD) and Na+ K+ ATPase and uptake of 65Zn in blood. The study revealed an increase in the levels of hemoglobin, % hematocrit, activities of delta-ALAD, Na+ K+ ATPase and uptake of 65Zn, 7 days after the 131I treatment. On the contrary, the levels of ZPP were found to be significantly decreased after 131I treatment. However, zinc treatment to 131I-treated animals significantly attenuated the various biochemical and hematological indices. Moreover, zinc treatment to the 131I-treated animals could significantly decrease the uptake of 65Zn, which was increased after 131I treatment. Based upon these data, the present study suggests that zinc has the potential to attenuate 131I induced toxicity by restoring the altered hematological indices and biochemical changes.

Bexarotene increases uptake of radioiodide in metastases of differentiated thyroid carcinoma

Treatment options for metastases of differentiated thyroid carcinoma (DTC) are limited due to decreased uptake of radioiodide (I-131). Therefore, strategies to improve I-131 uptake are mandatory. It has been suggested that retinoids have beneficial effects on iodide uptake in vitro and in humans. However, to date, only studies with 13-cis-retinoic acid have been performed in humans. We therefore decided to study the effects of 6 weeks of treatment with the retinoid X receptor activator bexarotene on I-131 uptake in patients with metastatic DTC. Open prospective intervention study. Twelve patients with metastases of DTC, with insufficient uptake of I-131, received 6 weeks of treatment with 300 mg bexarotene/day. Prior to, and after this intervention, I-131 uptake was measured by whole-body scintigraphy and single photon emission tomography (SPECT) 3 days after 185 MBq I-131. Diagnostic imaging was preceded by two consecutive injections of recombinant human TSH. Bexarotene treatment induced I-131 uptake in metastases of 8 out of 11 patients (one patient died for reasons not related to the study). However, uptake was only discernable at SPECT and had incomplete matching with metastases as visualized by CT scanning. Bexarotene partially restores I-131 uptake in metastases of DTC. The clinical relevance of this observation may be limited due to the differential responses of the different metastases within each patient and the low intensity of I-131 uptake.

Diagnose, Therapie und Nachsorge des differenzierten Schilddrüsenkarzinoms

For early diagnosis of thyroid cancer, ultrasonography (US) and US-guided fine-needle aspiration biopsy are the methods of choice. Thyroid scintigraphy using Tc-99m pertechnetate can underline the necessity of surgery in case of hypofunctioning nodules. Treatment of thyroid cancer includes total thyroidectomy and staging lymphadenectomy, in the case of lymph node metastases, radical neck dissection of the ipsilateral side. Four weeks after surgery, if TSH exceeds a value of 50 mU/l, with the exception of papillary thyroid cancer pT1a (TNM 1997), radioiodine remnant ablation using activities between 2960 and 3700 MBq I-131 is performed in all other cases. As growth of benign and malignant thyroid cells depends on TSH stimulation, thyroid hormone therapy using TSH suppressive doses (TSH, <0.03 mU/l) follows radioiodine remnant ablation. Additional fractionated external radiation therapy (50 Gy) may be administered in advanced cases (e.g., pT4 N1M0; TNM 1997). Standard follow-up of differentiated thyroid cancer includes measurement of serum thyroglobulin, US of the neck and I-131 whole-body scintigraphy (I-131 WBS). With about 98% the sensitivity of thyroglobulin is very high under TSH stimulation. In case of elevated thyroglobulin, US is the method of choice to detect local recurrences and lymph node metastases of the neck. At defined intervals of follow-up or in case of increasing thyroglobulin, I-131 WBS will be performed under TSH stimulation. With the availability of recombinant TSH (exogenous TSH stimulation) the need to withdraw thyroid hormone over a period of 3-4 weeks (endogenous TSH stimulation) is no longer necessary to perform I-131 WBS. However, in about 20-40% of cases or in the course of disease after several radioiodine therapies, recurrences or metastases may be or become iodine negative. In this case, cationic complexes such as Tc-99m Sestamibi or Tc-99m Tetrofosmin are available to detect less differentiated metastases. In the course of dedifferentiation of malignant thyroid cells, the ability of iodine uptake decreases and uptake of glucose increases. This elevated glucose metabolism can be imaged using FDG PET. Today the combination of PET (metabolic imaging) and CT (morphologic imaging) using PET/CT fusion imaging is the method of choice to image iodine-negative metastases.