Comparative scanning of thyroid nodules with technetium-99m pertechnetate and technetium-99m methoxyisobutylisonitrile

Thyroid imaging was performed using technetium-99m methoxyisobutylisonitrile and technetium-99m pertechnetate in 58 patients. The ^99mTc-pertechnetate scans showed a total of 77 nodules: 60 cold, 13 hot and 4 of normal activity. There was no ^99mTc-MIBI accumulation in 46.4% of ^99mTc-pertechnetate cold nodules; 27 (45%) of these nodules showed ^99mTc-MIBI uptake with the same intensity as the surrounding normal tissue, and five (8.6%) became hot with ^99mTc-MIBI. Of the ^99mTc-pertechnetate hot nodules 11 (84.6%) could not be differentiated from the normal extranodular tissue on the ^99mTc-MIBI scan. The histopathology of 34 surgically removed nodules proved that increased, normal or decreased ^99mTc-MIBI accumulation is not specific for thyroid malignancy and that the ^99mTc-MIBI uptake depends mainly on the viability of thyroid tissue.Correspondence to: I. Földes     

Identification of Warthin's tumor with technetium-99m pertechnetate

Salivary gland imaging with Tc-99m pertechnetate is a useful procedure for evaluating the functional status of salivary glands. The only neoplasms of salivary glands known to consistently concentrate Tc-99m pertechnetate are Warthin's tumor and oncocytoma. In the five cases presented, increased concentration of Tc-99m pertechnetate was seen in these tumors of the parotid glands. This finding was useful for preoperative identification of Warthin's tumor. During this investigation, the concentration of Tc-99m pertechnetate in Warthin's tumor varied by histologic type. Thus, a dynamic study may be helpful in evaluating the accumulation rate of Tc-99m pertechnetate into this tumor type. Because the retention of Tc-99m pertechnetate in tumor following stimulation is useful for the diagnosis of Warthin's tumor, a washout image is of importance in establishing this diagnosis.     

Stimulated salivary clearance of technetium-99m pertechnetate

A method to determine stimulated salivary clearance of pertechnetate is presented. It is easy to perform and separates normal patients (range 15.0 to 40.3 ml/min) from patients with known salivary disorders (range 1.2 to 10.6 ml/min).     

Localization of technetium-99m pertechnetate in peripheral nerve tumors

Technetium-99m pertechnetate scintigraphy in three patients with pathologically proven peripheral nerve tumors (six in total) demonstrated its ability to assess accurately the size, location, and the extent of all lesions. Pertechnetate localized only in areas of abnormal nerve involvement and all lesions were better seen in delayed images than the earlier ones. Pertechnetate imaging appears to be a promising method of noninvasive evaluation of clinically evident and occult tumors of peripheral nerve origin.     

Radiolabeling with technetium-99m to study high-capacity and low-capacity biochemical systems

After a brief review of the history of the development of technetium-99m-labeled radiopharmaceuticals, the use of technetium chelates in high-capacity systems is discussed. The latter are used in the study of five organ systems, the kidneys, liver, bone, brain, and heart. The chemical characterization of^99mTc complexes is also reviewed, followed by discussion of the various approaches to the labeling of proteins with direct labeling, the preformed chelate approach, and the antibody chelator conjugate approach. Thereafter, the labeling of biochemicals with^99mTc for use with easily saturated sites, e.g., receptors and enzymes, is considered. Finally, attention is given to factors that affect the preparation of high specific activity, high affinity^99mTc-labeled biochemicals.     

Biodistribution of technetium-99m pertechnetate after total colectomy in rats

This study evaluated the effects of total colectomy on the biodistribution of technetium-99m pertechnetate (^99mTcO₄^?) on the 28th postoperative day in rats. Samples of several organs were harvested for counting the percent of injected radioactivity/g of tissue (%ATI/g). The %ATI/g in colectomy rats was higher in the stomach and ileum than in sham and controls (p<0.05). Increase in mucosa and muscularis size of ileum was observed. Colectomy was associated with lower biodistribution in bladder and thyroid, T3, and T4, than in controls.     

Altered distribution of technetium-99m sodium pertechnetate associated with antimicrobial therapy

Three patients underwent brain scanning for evaluation of central nervous system disease and were simultaneously treated for infectious diseases unrelated to the central nervous process. All revealed intense vascular pooling on their brain images. The imaging studies had been performed following the administration of Tc-99m pertechnetate. None of the patients had prior nuclear medicine examinations to suggest the causal effect of stannous ion as a source of interference. All of the patients were on combination antimicrobial drugs: two on sulfamethoxazole and trimethoprim, and one on isoniazid and ethambutol. One patient revealed 75% Tc-99m red cell tagging. Another patient's repeat brain scan with Tc-99m DTPA revealed normal distribution. Our findings suggest that patients on antimicrobial combination drug regimens who require brain scans should be imaged routinely with agents other than Tc-99m.     

Thyrotoxic graves’ disease with normal thyroidal technetium-99m pertechnetate uptake

We saw 24 thyrotoxic Graves' patients with normal thyroidal uptake of technetium-99m pertechnetate (99mTc) out of 201 untreated thyrotoxic Graves' patients seen over 4 years. The clinical and laboratory findings for these patients were studied and analysed. Thyroid uptake and scintigraphic examinations by means of 99mTc, TBII and TSab activity measurement clearly distinguished these patients from other thyrotoxic disorders (destruction-induced thyrotoxicosis and autonomously functioning thyroid lesions). Different from other disorders, these patients had not lower but normal thyroid uptake and also showed diffuse and discrete trapping into the enlarged glands. These patients had significantly smaller goiters, a lower serum thyroid hormone level, and lower TBII and TSab activity, when compared with other high 99mTc uptake groups with Graves' disease, and their condition could be easily controlled with small amounts of antithyroid drugs. Our study indicates that thyrotoxic Graves' disease with normal 99mTc uptake exists and 99mTc uptake study and TBII activity measurement is very useful for the diagnosis. The normal 99mTc uptake thyrotoxic Graves' patient might be early stage patients with general Graves' disease and their early discrimination from general Graves' patients is very advantageous for treatment and prognosis.     

Role of technetium-99m pertechnetate scintigraphy in the management of extra-abdominal fibromatosis

The purpose of this study was to investigate technetium-99m pertechnetate (Tc-99m) as a tumor-scanning agent in patients with extra-abdominal fibromatosis, and to establish the sensitivity of this type of scintigraphy. Eleven patients with extra-abdominal fibromatosis were studied: all but one having postsurgical recurrences. Of the 11 patients, diagnosed histologically, 5 underwent repeated Tc-99m scintigraphic follow-up examinations. The injected 370 MBq Tc-99m gave us an early scintigram within 10 min and a delayed one 2 h later. For adequate comparison, the region of interest (ROI) of the scintigram was placed over the tumor. The tumor-to-background (T/BG) count ratio was computed. Extra-abdominal fibromatoses, even recurrences, were demonstrated scintigraphically in both the early and the delayed phase, in all 11 patients. The average T/BG ratio was 2.11 in the early scintigram and 2.15 in the delayed one. The sensitivity and the specificity were both 100%. Tc-99m scintigraphy has proved useful in detecting extra-abdominal fibromatoses and in the follow-up of patients.     

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.     

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.     

Comparison of technetium-99m MAG3 kit with HPLC-purified technetium-99m MAG3 and OIH in rats

Technetium-99m (99mTc) mercaptoacetylglycylglycylyglycine (MAG3) in high (greater than or equal to 95%) radiochemical purity is prepared from lyophilized kits containing benzoylMAG3, sodium tartrate, lactose, and stannous chloride by adding sodium [99mTC]pertechnetate and heating the contents briefly. Constant-infusion renal whole-blood clearance obtained with [99mTc] MAG3 kits was compared with that obtained with high performance liquid chromatography (HPLC) pure [99mTc]MAG3 and with co-infused iodine-131 (131I) iodohippurate (OIH) in anesthetized rats. Average renal whole-blood clearance of [99mTc]MAG3 from kits was 3.9 +/- 0.4 ml/min/100 g body weight (mean +/- s.e.m. n = 5) and that for HPLC-pure [99mTc]MAG3 was 4.6 +/- 0.3 (n = 3). Renal whole-blood clearance ratios for [99mTc]MAG3 to co-infused iodine-131 (131I) OIH were greater than unity for both kit formulation (1.7 +/- 0.1) and HPLC-pure [99mTc]MAG3 (1.9 +/- 0.2). Differences in these two measures were not significant. Plasma binding (determined from blood drawn at the end of the infusion) of [99mTc]MAG3 prepared from both kits (75 +/- 2%, n = 4) and HPLC-separation (76 +/- 4%) were greater than that of [131I]OIH in corresponding plasma samples (31 +/- 1% and 32 +/- 2%) respectively). Renograms performed in anesthetized rats revealed no statistically significant differences between kit-prepared [99mTc]MAG3 and [131I]OIH in terms of time-to-peak renal activity (5.0 +/- 1.7 min, n = 6; and 2.2 +/- 0.2 min, n = 3, mean +/- s.e.m. for [99mTc]MAG3 and [131I]OIH, respectively), in terms of time to fall to half-maximal activity (15.3 +/- 2.4 min and 9.6 +/- 2.1 min, respectively), or in terms of fraction of peak radioactivity in right kidney (0.53 +/- 0.01 for both substances). To assess possible interference from hepatobiliary uptake and excretion in renal failure, radioactivity in liver regions of interest was followed by gamma camera scintigraphy for 30 min after intravenous injection of [131I]OIH and kit and HPLC-purified [99mTc]MAG3 in anesthetized rats rendered anephric by ligating renal peduncles. Liver activity was 25% of total for both preparations of [99mTc]MAG3 and was 22% of total for [131I]OIH. There were no significant differences among the substances.     

Radiolabeling small RNA with technetium-99m for visualizing cellular delivery and mouse biodistribution

To develop a noninvasive direct method for the in vivo tracking of small interfering RNA (siRNA) used in RNA interference, two 18-nucleotide oligoribonucleotides were radiolabeled with technetium-99m ((99m)Tc-RNA). The ability of (99m)Tc-RNA to track delivery was tested in cultured cells and living mice. The cellular delivery of (99m)Tc-RNAs could be quantified by gamma counting and could be visualized by microautoradiography. Radiolabeled RNAs can be efficiently delivered into cells by reaching up to 3x10(5) molecules of small RNAs per cell. Moreover, RNAs were internalized with homogeneous distribution throughout the cytoplasm and nucleus. In tumor-bearing mice, whole-body images and biodistribution studies showed that (99m)Tc-RNAs were delivered to almost all tissues after intravenous injection. The imaging of living animals allowed noninvasive and longitudinal monitoring of the in vivo delivery of these small RNAs. In conclusion, using (99m)Tc radiolabeling, the delivery of small RNAs could be measured quantitatively in cultured cells and could be noninvasively visualized in living animals using a gamma camera. The results of this study could open up a new approach for measuring the in vivo delivery of small RNAs that might further facilitate the development of siRNAs as targeted therapies.     

Thyroid blood flow and uptake of technetium-99m pertechnetate in Graves' disease

The aim of this study was to assess the relation of early thyroid blood flow (EBF) and technetium-99m pertechnetate ((99m)TcO(-)(4)) uptake, as an early diagnostic index in patients with Graves' disease (GD) by dynamic thyroid scintigraphy (40 frames, 3 sec/frame). Thirty patients with GD with mean age 50.0 +/- 9.0 y, range: 35.0-69.0 y, were studied. The results obtained were compared with those of 30 euthyroid individuals (EI) of mean age 46.9 +/- 12.5 y, range: 22.0-68.0 y. The parameters of (99m)TcO(-)(4) EBF and early uptake studied, derived from the background subtracted time activity curves, were as follows: a) The duration of the EBF in sec; b) The perfusion index (PI) - the ratio of counts at the beginning and at the end of the EBF; c) The uptake index 1 (UI1)- the counts ratio between the counts at the end of the EBF and at the 2nd min d) The uptake index 2 (UI2) - the counts ratio between the 1st min and the 2nd min of the uptake curve and e) Delayed (99m)TcO(-)(4) thyroid uptake (TcTU) at 20 min was also calculated as a percentage of net counts activity accumulated in the thyroid gland at 20 min. Results were as follows: a) The mean values of the duration of the EBF were shorter in GD patients (9.90 +/- 2.94 sec) than in EI (15.70 +/- 4.01 sec; P<0.0001); b) PI did not differ significantly (P>0.05); c) The mean UI1 and UI2 values of thyroid uptake of 99m TcO4- were significantly lower in GD (UI1=0.621, UI2=0.772) as compared to EI (UI1=1.106, UI2=0.947; P<0.0001 for both) and d) TcTU values were significantly higher in GD (13.6%) than in the group of EI (1.29%; P<0.0001). A good correlation was found in patients with GD between early (UI1 and UI2) and delayed TcTU (r = -0.562; P=0.010 and r = -0.459; P=0.042 respectively). Also, in patients with GD the EBF correlated poorly with UI1, UI2 and TcTU (P>0.05 for all these parameters). In conclusion, the results of this study indicate that the duration of EBF did not relate significantly to the height of TcTU values in patients with GD. On the contrary, the early uptake, indices UI1 and especially UI2 were shown to be faster in the majority of GD patients and correlated well with the TcTU. These parameters may be used as diagnostic indices for GD. Further investigation is required to support the above findings.