The radioactive handkerchief sign. A contamination artifact in I-131 imaging for metastatic thyroid carcinoma

False-positive findings suggestive of metastatic functioning thyroid carcinoma have been well documented in I-131 whole-body imaging. These artifacts are often associated with contamination from radioiodine-containing body secretions. Recently, a contaminated handkerchief on an iodine-131 whole-body scan was reported. In the following study, two additional cases involving the sequestration of I-131 contaminated handkerchiefs in patients' pockets are presented, and the literature regarding these false-positive findings is reviewed. Although rare, this "radioactive handkerchief sign" may cause serious misinterpretation of a focal radioiodine accumulation.     

Axillary iodine-131 accumulation due to perspiration

A case of spurious axillary uptake of I-131 proven to be caused by perspiration is presented. False-positive localizations of radioiodine, both pathologic and physiologic, are reviewed to avoid confusion of these entities with functioning thyroid carcinoma metastases.     

Sialadenitis mimicking metastatic thyroid carcinoma

In the post-thyroidectomy patient who has received I-131 ablation for thyroid carcinoma, focal uptake on repeat total body images is usually interpreted as being indicative of functioning thyroid metastases. The differential of focal I-131 activity in such a patient has been described. This report adds to the differential by presenting a case of benign sialadenitis that caused focal neck uptake a year after ablation therapy with I-131.     

Accumulation of technetium-99m pertechnetate in a patient with metastases of thyroid carcinoma

Accumulation of both Tc-99m pertechnetate and radioiodine upon scintigraphy in thyroid carcinoma and/or in its metastases is a rare occurrence. In this paper we describe a patient who was taken to surgery for left lobectomy of the thyroid with follicular adenocarcinoma and who had accumulation of both I-131 and Tc-99m pertechnetate in lung metastases. The accumulation of I-131 was less than that of Tc-99m pertechnetate. The use of Tc-99m pertechnetate for imaging for diagnosis of functioning thyroid metastases is discussed.     

Effect of reserpine on salivary gland radioiodine uptake in thyroid cancer

Nine patients with thyroid cancer were treated with reserpine in an attempt to reduce radiation exposure to the salivary glands from 100-150 mCi doses of I-131 therapy to thyroid remnants or metastases. Three control patients were not treated with reserpine but did receive 100-150 mCi of I-131. Parotid/background ratios of activity after radioablative doses of I-131 in patients not treated with reserpine were significantly higher than the patients treated with reserpine, and this was also true seven days after the radioablative dose. Combined therapy with reserpine, chewing gum, lemon candies, and hydration is suggested for the prevention of sialadenitis and xerostomia due to large doses of radioiodine.     

Compare FDG-PET and Tc-99m tetrofosmin SPECT to detect metastatic thyroid carcinoma

RATIONALE AND OBJECTIVES: The effectiveness of 18-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) and technetium-99m tetrofosmin (Tc-99m TF) single photon emission computed tomography (SPECT) of neck and chest was evaluated to detect metastatic lesions in well-differentiated thyroid carcinoma after nearly total thyroidectomy and radioiodine (I-131) treatment who present with elevated serum human thyroglobulin levels but negative I-131 whole body scan. MATERIALS AND METHODS: Twenty-three patients with differentiated thyroid carcinoma who underwent nearly total thyroidectomy and I-131 treatments were included in this study. RESULTS: All of the 23 patients had negative I-131 whole body scan and elevated human thyroglobulin levels under thyroid-stimulating hormone stimulation. Metastatic lesions were detected by FDG-PET in 20 patients, while Tc-99m TF SPECT revealed metastatic lesions in only 11 of the 20 patients. Both FDG-PET and Tc-99m TF SPECT failed to demonstrate miliary pulmonary metastases in two of the remaining three patients. The other patient did not show any lesion on FDG-PET, Tc-99m TF SPECT, chest computed tomography, or other imaging techniques. CONCLUSION: This study demonstrated that FDG-PET is more sensitive than Tc-99m TF SPECT to detect metastatic lesions in differentiated thyroid carcinoma with elevated human thyroglobulin but negative I-131 whole body scan. However, miliary pulmonary metastases could be missed by the both techniques.     

Radiation Dose Assessment for I-131 Therapy of Thyroid Cancer Using I-124 PET Imaging

The goal for this work was to develop a method to determine the feasibility of estimating absorbed dose distribution of I-131 thyroid therapy using I-124 PET images of residual thyroid lesions with the dose constraint of 200 cGy to blood, that is a surrogate for bone marrow toxicity. A dose response study has been carried out on 3 patients with papillary thyroid carcinoma. Those patients were given 15-37 MBq of I-124 along with 74-185 MBq of I-131. PET imaging was performed 2-4 hour and then at 24 hour and either 48 hour, or 72 hour post-infusion. Lesion masses were computed from PET images using an adaptive thresholding technique. The definition of the boundary enabled determination of the iodine activity within the lesion. Time-activity curves were fitted to estimate the cumulated activity and therefore the absorbed dose per MBq administered. Daily blood and total body counts were performed on the patients using a multichannel analyzer with windows set for both I-131 (364 keV) and I-124 (511 keV). Cross-talk corrections from one isotope into the alternate window was determined using a standard of each respective isotope. At maximum-tolerated-activity (MTA) that delivers 200 cGy radiation dose to the blood, the dose to lesions from I-131 varied from 0.04 to 2.44 cGy/MBq (1.57-90.48 rads/mCi) with effective half-lives for I-124 ranging from 0.58 to 1.86 days. The three-dimensional absorbed dose distribution in the thyroid lesions was calculated by convolving the activity values with an I-131 point-source kernel using a Fast Hartley Transform. The calculated mean absorbed dose distribution was displayed as isodose lines on PET images that can be used to refine the amount of administered activity. PET with I-124 may improve the absorbed dose estimates from radioiodine therapy with I-131 in the treatment of thyroid cancer. The capability of estimating I-131 mean absorbed dose distributions from serial I-124 PET images can lead to patient-specific treatment planning for thyroid therapy.     

Accumulation of iodine-131 and technetium-99m pertechnetate in thyroid carcinoma

Carcinoma of the thyroid is usually delineated as a cold defect on images with radioiodine and Tc-99m per-technetate. However, several cases that showed an accumulation of Tc-99m pertechnetate in thyroid carcinoma or in their metastases, but did not show any accumulation of radioiodine, have been reported. This paper presents a rare case of an advanced follicular adenocarcinoma of the thyroid that accumulated both Tc-99m pertechnetate and I-131. In this 41-year-old male patient, there were two primary foci in the thyroid; one occupied the whole left lobe with extension to the mediastinum and the other located in the lower part of the right lobe. In addition, there was a lymph node metastasis in the upper mediastinum adjacent to the left lobe. On images with both I-131 and Tc-99m pertechnetate, the tumor in the left lobe and the metastatic lymph node were delineated, but the tumor in the right lobe was not. Accumulation of Tc-99m pertechnetate in the lower part of the tumor of the left lobe was more distinct than that of I-131. Therefore, it is considered that despite similar histologic findings the trapping ability of the cancerous tissue differed from area to area.     

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.     

FDG positron emission tomographic, radioiodine, and MIBI imaging in a patient with poorly differentiated insular thyroid carcinoma.

Poorly differentiated insular thyroid carcinoma is now classified as a separate entity among other tumors of the thyroid gland. Its histologic pattern and its clinical course are regarded as intermediate between well differentiated and anaplastic thyroid cancer. Insular carcinoma accumulates I-131, but no data exist regarding its fluorodeoxyglucose (FDG) positron emission tomographic (PET) uptake. The authors report F-18 FDG PET, Tc-99m MIBI, and radioiodine imaging features in a 63-year-old patient with metastatic insular thyroid carcinoma. After total thyroidectomy (for poorly differentiated insular carcinoma pT3a), the patient was referred for radioiodine ablation. No signs of recurrence were present until 16 months later, when thyroglobulin levels increased. An I-131 scan showed a single lesion in the right lung, and further radioiodine treatment was administered (cumulative dose [530 mCi], 19,610 MBq I-131). Three years after the initial diagnosis, FDG-PET and Tc-99m MIBI scans were performed within 5 days during thyroxine treatment. After that, thyroxine substitution was withdrawn; 6 weeks later, an I-131 whole-body scan was performed. Both radioiodine and MIBI images showed increased tracer uptake in the known lung lesion. However, FDG PET showed a normal tracer distribution. Magnetic resonance and computed tomographic imaging confirmed a 12-mm lesion in the right upper lobe. These findings support the concept of the "flip-flop phenomenon" in insular thyroid carcinoma, an alternating pattern of metastases with either I-131 or FDG-uptake. Despite poorly differentiated histologic findings, glucose metabolism was not increased in this patient with an insular tumor.     

I-123 whole body scanning: case report and discussion

PURPOSE: In managing differentiated thyroid carcinoma, concern over the stunning that may occur with traditional whole body imaging using I-131 has fostered an interest in using I-123 for this purpose. A case is presented as a focus for discussion of the issues, with special reference to accuracy and the effect thereon of technical factors. CASE REPORT: A 43-year-old man with papillary carcinoma of the thyroid was scanned after thyroidectomy using 10 mCi I-123. Images at 24 and 48 hours demonstrated foci including multiple regional metastases. They were less well demonstrated in images 7 days after therapeutic I-131, and negative imaging 1 year later implied therapeutic success. DISCUSSION: I-131 has the advantages of a longer half-life, facilitating delayed imaging and lower price. I-123 has the advantages of favorable gamma-ray energy and less useless radiation to thyroid tissue and the whole body. Despite its short half-life, with a sufficient amount, images at 48 hours are practical. In the case presented, there are several possible reasons why superior lesion detection occurred in diagnostic I-123 images. In any case, the outcome demonstrates that I-131 posttherapy images are not an absolute "gold standard" for accuracy. Investigations comparing I-123 with I-131 imaging have been subject to biases, including insufficient dose of I-123, lack of delayed I-123 imaging, suboptimal collimation for I-131, and the relatively high dose of I-131 in posttherapy scanning. CONCLUSIONS: The evidence, although not definitive, strongly suggests that I-123 is at least as accurate for diagnostic whole body imaging as I-131.     

FDG-PET performed concurrently with initial I-131 ablation for differentiated thyroid cancer

Objective  

Differentiated thyroid cancers (DTCs) are commonly treated by total thyroidectomy followed by I-131 radioiodine ablation to eradicate any residual thyroid tissue and to detect any metastatic lesions on post-treatment whole body scans (TxWBS). However, some DTCs do not trap iodine, resulting in negative whole body scanning. Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) has proven to be a valuable diagnostic technique for detecting many types of malignant tumors and metastases. The purpose of this study was to evaluate FDG-PET performed concurrently with initial I-131 ablation for its ability to detect lymph node metastasis and for its role in the management of DTC patients.     

Radioactive iodine treatment of metastatic thyroid carcinoma with clinical thyrotoxicosis

We present a case of well-differentiated follicular carcinoma of the thyroid with hyperfunctioning metastases and clinical thyrotoxicosis. The recommended I-131 treatment dose for patients with widespread bone metastases from thyroid carcinoma is 200 mCi. However, in a patient with hyperfunctioning metastatic tumor and increased radioiodine uptake, the treatment dose should be modified. Radiation dosimetry measurements performed on the patient in this study demonstrated that 132 mCi would be a safe therapeutic I-131 dose which would avoid injury to normal radiosensitive tissues. Consequently, she was given a 130-mCi therapeutic dose.     

Differentiated thyroid cancer presenting with thyrotoxicosis due to functioning metastases

Thyrotoxicosis due to functioning metastases in differentiated thyroid cancer (DTC) is exceedingly rare. We report a case of follicular carcinoma in a 54-year-old manager, who presented with thyrotoxicosis, shortness of breath and lung metastases. Transbronchial biopsy of a pulmonary nodule demonstrated normal thyroid. This was interpreted as representing very well-differentiated thyroid cancer. CT, (131)I whole-body imaging and dosimetry is described following total thyroidectomy and repeated radioiodine administration (cumulative activity 34.6 GBq). The patient became asymptomatic with almost complete eradication of the pulmonary metastases. Potential complications of thyroid storm, bone marrow failure and pulmonary fibrosis following radioiodine are discussed, together with methods to minimise these risks.     

The use of technetium-99m pertechnetate in postoperative thyroid carcinoma. A comparative study with iodine-131

Over 3 years, a prospective comparison was made between Tc-99m pertechnetate and I-131 for the detection of residual and metastatic tissue in the follow-up of patients with cancer of the thyroid. All patients stopped thyroid medication for a minimum of 4 weeks. All patients had imaging done first with Tc-99m pertechnetate followed within a maximum of 2 weeks by I-131. The study included 66 patients in whom 81 studies were done with both Tc-99m and I-131. The results showed that 27 studies were positive with both Tc-99m and I-131 (true positive): 19 in the thyroid bed, four lymph nodes, two bony metastases, and two pulmonary metastases. Five patients had negative results with Tc-99m and positive results with I-131 (false negative): three in the thyroid bed, one lymph node metastasis, and one pulmonary metastasis. Only one case was positive with Tc-99m in the neck but negative with I-131 (false positive). The remaining 48 studies were negative both with Tc-99m and I-131 (true negative). Considering I-131 imaging as the standard procedure, Tc-99m had a sensitivity of 87%, specificity of 97%, and accuracy of 92.5% for the detection of residual or metastatic functioning thyroid tissue.     

False-positive I-131 accumulation in a hepatic hydatid cyst

In this report, a case of differentiated thyroid carcinoma having false-positive I-131 accumulation due to a large hydatid cyst in the liver is presented. Abdominal sonographic examination of a 37-year-old patient with differentiated thyroid carcinoma demonstrated an ovoid, complex cystic mass containing cystic parts as well as solid-appearing components in the right lobe of liver, which is concordant with a type CE-3 hydatid cyst. The postablative whole-body scan obtained 10 days after 100 mCi I-131 therapy displayed intense and homogeneous uptake of radioiodine in the liver. Hepatic cystic mass was removed, and postoperative histologic evaluation confirmed hydatid disease. Some cystic lesions of the kidney and liver have been previously reported as causes of false-positive radioiodine accumulation.     

Insensitivity of Tc-99m pertechnetate for detecting metastases of differentiated thyroid carcinoma

To evaluate the use of Tc-99m pertechnetate whole body scanning for the detection of metastases of differentiated thyroid carcinoma, the authors performed sequential Tc-99m pertechnetate and I-131 scans in five patients with known or suspected metastatic thyroid cancer. All five patients had abnormal I-131 uptake, but only two patients had abnormal Tc-99m pertechnetate uptake. A total of 33 abnormal foci were located with I-131; Tc-99m pertechnetate detected only 3 of these foci, and did not demonstrate any foci that were not apparent with I-131. Despite the theoretical advantages of Tc-99m pertechnetate, it cannot be recommended as a substitute for I-131 for locating thyroid cancer metastases.     

Technetium-99m tetrofosmin single photon emission computed tomography to detect metastatic papillary thyroid carcinoma in patients with elevated human serum thyroglobulin levels but negative I-131 whole body scan

AIM: The aim of this study was to evaluate the effectiveness of technetium-99m tetrofosmin (Tc-99m TF) single photon emission computed tomography (SPECT) of the neck and chest to detect metastatic lesions in papillary thyroid carcinoma (PTC) after near total thyroidectomy and radioiodine (I-131) treatment in patients who present with elevated serum human thyroglobulin (hTg) levels but negative I-131 whole body scan (WBS). MATERIALS AND METHODS: Twenty patients with PTC treated by near total thyroidectomy and I-131 treatments were included in this study. All 20 patients had negative I-131 WBS results and elevated hTg levels (hTg 2.0 microIU/ml) under thyroid-stimulating hormone (TSH) stimulation (TSH 30 microIU/ml). Nineteen of the 20 cases were confirmed to have metastases by operation/biopsy histopathological findings or clinical follow-up longer than 1 year by additional morphological imaging techniques. The remaining patient has been followed up closely and has been disease free for 10 months. Tc-99m TF SPECT was performed to detect metastatic lesions. RESULTS: Tc-99m TF SPECT demonstrated lesions in 11/19 patients; a sensitivity of 57.9%. Tc-99m TF SPECT failed to demonstrate lesions in eight patients including smaller lymph nodes and miliary lung metastases. CONCLUSIONS: We conclude that Tc-99m TF SPECT is a useful additional tool to detect metastatic lesions in PTC with elevated hTg but negative I-131 WBS. However, smaller lymph nodes and miliary lung metastases may be missed.     

Bronchoalveolar carcinoma of lung masquerading as iodine avid metastasis in a patient with minimally invasive follicular carcinoma of thyroid

A 52-year-old man with follicular thyroid carcinoma was administered 182 mCi of radioiodine (I-131) a month after total thyroidectomy. Post-therapy scan revealed diffuse uptake of radioiodine in the apical left lung. CT-guided biopsy of this mass revealed mucinous bronchoalveolar carcinoma. Immunohistochemistry for thyroglobulin was negative. An FDG PET scan showed avid uptake in the lung mass. Surgery was ruled out, so he was given chemotherapy, without benefit. The lesion continued to show I-131 uptake even while on daily T3 substitution, suggesting that the mass was thyroid stimulating hormone-independent. Because the mass showed I-131 uptake and chemotherapy was not beneficial, it was decided to treat with I-131. He was continued on T3 substitution therapy and was given 209 mCi of I-131. Follow-up CT scan a few weeks later reported a 1-cm all round reduction of the mass. I-131 scan showed avid tracer uptake in the mass. This case suggests the possibility of this therapeutic option in nonthyroidal tumors that may concentrate radioiodine.     

Radioiodine uptake by metastatic nonthyroidal adenocarcinoma of the lung in a patient with papillary thyroid carcinoma

A 49-year-old woman with a history of a hysterectomy for carcinoma of the cervix and papillary thyroid carcinoma showed multiple pulmonary metastases on chest radiography. An I-131 scan revealed multiple areas of increased uptake in the chest. These lesions were found to be metastatic cervical adenocarcinoma. The radioiodine uptake by the metastatic cervical adenocarcinoma of the lungs occurred in the presence of normal thyroid imaging in a patient with a thyroid nodule and papillary thyroid carcinoma.