Clinical conditions related to positive thymic uptake on I-131 post-therapeutic scans in thyroid cancer patients.

OBJECTIVE: Thymic uptake is a well-known cause of false-positives on I-131 post-therapeutic scans. This study identified the clinical conditions associated with thymic uptake on I-131 post-therapeutic scans in thyroid cancer patients. DESIGN: This was a retrospective study that investigated the clinical conditions associated with thymic uptake on I-131 post-therapeutic scans of patients obtained between January 2010 and December 2010. PATIENTS: Six hundred and eighty-five patients were included follwing a therapeutic dose of I-131 (3.7-9.25 GBq). METHODS: We reviewed the patients' clinical characteristics, including age, sex, histology, serum thyrotropin (TSH) stimulation regimen, prior history of RAI therapy, and labaratory parameters such as the serumTSH, thyroglobulin, and anti-thyroglobulin antibody. At follow-up, patients were assessed in terms of disease-free status, structural persistence, and biochemical disease. RESULTS: In total, 107 I-131 post-therapeutic scans (15.6%) evidenced thymic uptake. The mean age of the positive thymic uptake group was significantly lower than that of the negative group (p < .001). Significant indicators for thymic uptake were thyroid hormone withdrawal and a history of repeated radioactive iodine (RAI) therapy (p < .05). Logistic regression analysis showed that young age and a history of repeated RAI therapy correlated with thymic uptake (p < .001). At the end of follow-up, 487 patients (86.5%) were disease-free, 44 (7.8%) still had biochemical disease, and 32 (5.7%) showed structural persistence. Ten patients (11.5%) in the positive thymic uptake group and 22 (4.6%) in the negative thymic uptake group showed structural persistence. Five patients (5.7%) in the positive thymic uptake group and 39 (8.2%) in the negative thymic uptake group had biochemical disease. The final follow-up results of the two groups were statistically different. CONCLUSIONS: Thymic uptake tended to be more prominent in young patients with a history of repeated RAI therapy. Structural recurrence during follow-up was much more common in the positive thymic uptake group, while the incidence of biochemical recurrence during follow-up was higher in the negative thymic uptake group.

Asymptomatic Large Pulmonary Arteriovenous Malformation Masquerading as a Metastatic Deposit in a Patient with Papillary Thyroid Carcinoma.

Adult cases of congenital arteriovenous malformation (AVM) of the mediastinum are extremely rare, and because of their varied clinical presentations, they pose a diagnostic challenge. There is no reported association of pulmonary AVM and papillary thyroid carcinoma. We describe a 38-year-old female with a large right lung AVM, multinodular goiter, and high serum thyroglobulin (Tg) with papillary thyroid carcinoma. The lung mass was believed to represent a pulmonary metastatic deposit due to high Tg value. Whole body I-131 scan and FDG PETMR imaging were performed as part of the workup.

Ovarian teratoma mimicking metastasis on I-131 scan : a case report.

The whole body I-131 scan is routinely performed in the postoperative treatment of patients with well-differentiated thyroid cancer. Accurate interpretation of whole body I-131 scan after thyroidectomy is critical to appropriate management of patients with thyroid cancer, to prevent unnecessary surgical removal or exposure to radioiodine. Unfortunately, false-positive uptakes in several other organs and their associated disease processes have been reported. We report a case of false-positive iodine uptake in the pelvic region with incidentally diagnosed mature cystic teratoma.

New Intraspinal cause of physiological FDG uptake.

We present a paediatric case of Papillary Ca thyroid under evaluation for elevated Thyroglobulin (Tg) level with negative (131)I wholebody scintigraphy. Differentiated thyroid cancer (DTC) arises from follicular epithelium and retains basic biological features like expression of sodium iodide symporter (NIS), which is the cellular basis of radio iodine ((131)I) concentration during thyroid ablation. Once dedifferentiation of thyroid cells occurs, cells fail to concentrate (131)I, posing both diagnostic and therapeutic problems in DTC and one may have to resort to other imaging techniques for disease localization. As DTC progression is slow, patients have a relatively good prognosis. However children with thyroid malignancies need aggressive management, as initial presentation itself maybe with nodal metastases. It is well known that FDG PET CT apart from its oncological applications, is also used in the evaluation of vascular inflammation especially Takayasu's arteritis. It is also reported in literature, that (18)F-FDG uptake can be seen relatively frequently in the arterial tree of cancer patients. Dunphy et al reported the association of vascular FDG uptake in inflammation as well as in normal arteries. This study typically describes FDG uptake in a patchwork of normal vessel, focal inflammation and or calcification of vessels. The other plausible reasons for significant vascular (18)F-FDG uptake are drugs such as potent non steroidal anti-inflammatory agents, dexamethasone, prednisone and tacrolimus. Our patient showed false positive (18)F Fluorodeoxyglucose (FDG) uptake in spinal cord at D11/12 and D12/L1 vertebral levels in FDG PET CT imaging performed as part of raised Thyroglobulin workup. This intra spinal FDG uptake is attributed to physiological uptake and inadequate FDG clearance from artery of Adamkiewicz, which can be added as a new physiological cause of FDG uptake unreported in literature as yet.

Optimal Imaging Time for Diagnostic I-123 Whole Body Scan in the Follow-up of Patients with Differentiated Thyroid Cancer: Comparison between 6- and 24-Hour Images of the Same Subjects / 핵의학분자영상

PURPOSE: To determine optimal imaging time for diagnostic I-123 whole body scan in the follow-up of patients with differentiated thyroid cancer (DTC), we compared the image quality of 6- and 24-hour images of the same subjects. MATERIALS AND METHODS: Four hundred ninety-eight patients (M:F=55:443, Age 47.6+/-12.9 years) with DTC who had undergone total thyroidectomy and I-131 ablation therapy underwent diagnostic whole body scanning 6 hour and 24 hour after oral ingestion of 185 MBq (5 mCi) of I-123. Serum thyroglobulin measurement and ultrasonography of the neck were performed at the time of imaging. In 40 patients underwent additional I-131 therapy, post-therapy I-131 images were obtained and compared with diagnostic I-123 images. RESULTS: In 440 patients (88.4%), 6- and 24-hour diagnostic I-123 images were concordant, and 58 patients (11.6%) showed discordant findings. Among 58 discordant patients, 31 patients showed abnormal tracer uptake on only 6-hour image, which turned out false-positive findings in all cases. In 12 patients with positive findings on only 24-hour image, remnant thyroid tissue (4 patients) and cervical lymph node metastasis (3 patients) were presented. Among 40 patients underwent additional I-131 therapy, 6-hour and 24-hour images were discordant in 13 patients. All 5 patients with abnormal uptake on only 6-hour image revealed false-positive results, whereas most of 24-hour images were concordant with post-therapy I-131 images. CONCLUSION: I-123 imaging at 24-hour could reduce false-positive findings and improve diagnostic accuracy, compared with 6-hour image in the follow-up of patient with DTC.

False-positive I-131 Scan by Contaminated Muffler in a Patient with Thyroid Carcinoma / 핵의학분자영상

A 39-year-old female patient who had undergone a total thyroidectomy for a papillary thyroid carcinoma underwent a whole body scan with I-131. The I-131 scan was performed 72 hours after administering 185 MBq (5 mCi) of an I-131 solution. The anterior image of the head, neck, and upper chest showed multiple areas of increased uptake in the mediastinal area considering of functional metastasis. However, radioactivity was not evident in the image taken after removing her clothes and muffler. The image obtained after placing the muffler on the pallet showed that the radioactivity was still present. It is well known that artifacts on an I-131 scan can be produced by styling hair sputum, drooling during sleep, chewing gum, and paper or a cloth handkerchief that is contaminated with the radioactive iodine from either perspiration or saliva. This activity might be mistaken for a functional metastasis. Therefore, it is essential that an image be obtained after removing the patient's clothes. In this study, artifacts due to a contaminated muffler on the I-131 scan were found. These mimicked a functional metastasis of the mediastinal area in a patient with a papillary thyroid carcinoma.

Clinical Applications of 18-FDG PET in Recurred Differentiated Thyroid Cancer with Negative 131I Whole Body Scintigraphy: A Comparative Analysis with 99mTc-MIBI Scintigraphy / 대한내분비학회지

BACKGROUND: In patients with differentiated thyroid cancer treated by surgery and radioactive iodine ablation, serum thyroglobulin(Tg) and 131I whole body scan(WBS) are recognized as being the best cooperative indicators for detection of recurrence or metastasis. However, in some cases, 131I WBS shows no specific lesions despite elevated serum Tg. Therefore, 18-Fluorine-fluorodeoxyglucose (FDG) positron emission tomography(PET) has emerged as a useful method for the detection of 131I WBS negative thyroid cancers. The aims of the present study are to evaluate the clinical usefulness of this technique in detection and to compare the results with 99mTc-MIBI scintigraphy(MIBI) in cases of final results being confirmed by histologic diagnosis and other imaging methods. METHODS: We conducted a retrospective analysis amon 131I WBS negative recurred papillary thyroid carcinoma patients(male: female ratio=9:22, median age=42 yr). FDG PET was performed in 28 patients and MIBI 28 patients, 25 of whom were common to both groups. All patients had histologically proven recurrence/metastasis and negative 131I WBS results but persistently elevated serum Tg levels. In each case overall clinical evaluations were performed including histology, cytology, thyroglobulin level, other imaging methods, posttherapy 131I WBS and subsequent clinical course, to allow comparison with the results of FDG PET. RESULTS: In 19 cases of patients with negative 131I WBS, proven recurrence/metastasis lesions were detected in FDG PET. Compared with MIBI, FDG PET was found to be superior in 8 cases(including 2 patients with distant metastases). No FDG-negative/MIBI-positive tumor was observed. One FDG PET negative and MIBI negative case was proven 3 months later to be metastatic cervical lymph nodes, Sensitivities were 94.7% in the FDG PET group and 52.6% in MIBI. Diagnostic accuracy of FDG PET was superior to that of MIBI(93% vs. 62%, respectively, p=0.003). CONCLUSION: Our results confirmed the clinical usefulness of FDG PET for detection of 131I negative differentiated thyroid cancers and suggested the value of FDG PET as an initial diagnostic step, rather than MIBI, in these cases.

Usefulness of Tc-99m MIBI Scan in the Postoperative Follow Up Of Well-Differentiated Thyroid Cancer / 대한핵의학회잡지

To evaluate the clinical utility of Tc-99m MIBI scan in the detection of residual thyroid tissue or metastatic lesion in postoperative thyroid cancer patients, we compared Tc-99m MIBI scan with I-131 diagnostic and therapeutic scan in 30 postoperative well-differentiated thyroid cancer patients. Thyroglobulin levels of both on and off thyroid hormone medication and antithyroglobulin antibody were tested [Tg(on), Tg(off)l Positive rates for I-131 diagnostic and Tc-99m MIBI scan were 81% and 68% respectively. Concordance between I-131 diagnostic and Tc-99m MIBI scan was observed in 15 cases; 12 positive and 3 negative respectively Among the 6 cases with negative I-131 diagnostic scan and positive Tc-99m MIBI scan, 4 were positive in the therapeutic I-131 scan. We concluded that Tc-99m MIBI scan maybe a useful complementary modality to the currently established method of I131 scan and serum thyroglobulin level in the detection of recurrent or metastatic thyroid cancer, especially in the case of negative I-131 diagnostic scan.