Parathyroid scintigraphy: comparison of technetium-99m methoxyisobutylisonitrile and technetium-99m tetrofosmin studies

We report the preliminary results of a prospective study demonstrating tetrofosmin uptake in surgically and histologically proven parathyroid adenomas. In ten patients with primary chronic hyperparathyroidism, parathyroid imaging was performed using (1) technetium-99m methoxyisobutylisonitrile (MIBI) and (2)^99mTc-1,2-bis(bis(2-ethoxyethyl)phosphino)ethane (tetrofosmin) within a time interval of 3–5 days. Both tracers correctly identified the parathyroid adenomas by focal prolonged tracer retention. On visual inspection image contrast was generally higher with MIBI than with tetrofosmin in all the patients studied. Tetrofosmin showed a slower elimination from the parathyroid adenomas than MIBI in six of the ten cases. Our preliminary results show that tetrofosmin, like MIBI, as a feasible, sensitive tracer for parathyroid scintigraphy. For routine use, the rapid kit preparation without heating and the lower radiation dose to the patient make tetrofosmin an alternative tracer for parathyroid scintigraphy. Further evaluation is needed to determine which of the two tracers is the more sensitive for the detection of parathyroid adenomas, and which tracer properties better reflect the degree of endocrine activity.[/p]     

Cardiac blood-pool scintigraphy using technetium-99m DTPA-HSA: comparison with in vivo technetium-99m RBC labeling

We performed cardiac blood-pool scintigraphy using technetium-99m diethylenetriaminepentaacetic acid human serum albumin [( 99mTc] DTPA-HSA), a newly developed blood-pool agent, in 31 patients with various heart diseases and evaluated its clinical usefulness in comparison with the conventional in vivo 99mTc red blood cell (RBC) labeling. Excellent cardiac blood-pool images were obtained by [99mTc]DTPA-HSA method. Biodistribution studies showed higher accumulation of [99mTc]DTPA-HSA than that of 99mTc RBC in the lungs and liver, but similar count ratios of the cardiovascular blood pool to whole body between the two methods. In ECG-gated end-diastolic images, no quantitatively significant difference was observed in left ventricular target-to-background ratios between these two methods. Left ventricular ejection fraction (LVEF) calculated by [99mTc]DTPA-HSA MUGA method was correlated well with that by contrast LVEF (r = 0.91). No side effects were observed in any patient. In conclusion, cardiac blood-pool scintigraphy using [99mTc] DTPA-HSA is readily performed by single i.v. injection and useful for the assessment of cardiac function.     

Neurenteric cyst diagnosed by technetium-99m pertechnetate sequential scintigraphy

Neurenteric cysts are rare congenital anomalies which present as mediastinal tumors associated with vertebra anomalies. Two-thirds of them are lined with gastric mucosa and are potentially life threatening. An exact differential diagnosis is difficult preoperatively but is absolutely necessary because of the grave prognosis if left untreated. We present a case in which [99mTc]pertechnetate sequential scintigraphy demonstrated gastric mucosa in the cyst and helped to confirm the diagnosis. The scintigraphic findings are correlated with radiologic, sonographic, and pathologic features.     

Colonic varices demonstrated by technetium-99m red cell scintigraphy

Colonic varices is a rare condition, generally associated with portal hypertension, which normally presents as acute, severe, gastrointestinal blood loss. A case is presented in which the varicosities were observed serendipitously in a patient with a pancreatic tumor, in whom the bleeding was not variceal but due to two small unrelated gastric hemangiomas. The literature is reviewed and scintigraphic features described.     

Portal circulation by technetium-99m pertechnetate per-rectal portal scintigraphy

Portal circulation in patients with chronic liver diseases was evaluated by [99mTc]pertechnetate per-rectal scintigraphy. Technetium-99m pertechnetate (10 mCi) was instilled into the upper rectum, and serial scintigrams were taken. Radioactivity curves for the liver and heart were then recorded sequentially. Through analysis of these curves, the per-rectal portal shunt index (Sl) was calculated for six healthy subjects and 228 patients, 59 with chronic hepatitis, seven with idiopathic portal hypertension, six with primary biliary cirrhosis, and 156 with cirrhosis. In the healthy subjects, the Sl was 1.9-5.2% (mean 4.1%). In hepatitis, the mean Sl was 7.1%, and in cirrhosis, 52.9%. The Sl was higher in cirrhotic patients with esophageal varices than in those without (p less than 0.001), and in cirrhotic patients with encephalopathy than in those without (p less than 0.01). For some patients with portal hypertension, portal collateral circulation could be depicted, and images of changes in the portal collateral circulation after vascular anastomosis were seen.     

Intraperitoneal hemorrhage diagnosed by technetium-99m labeled RBC imaging

During examination for occult gastrointestinal bleeding, Tc-99m labeled RBC imaging demonstrated intraperitoneal bleeding into Morrison's pouch from a hepatocellular carcinoma.     

Gamma scintigraphy using Tc-99m labeled antibody to human chorionic gonadotropin

A case report is presented describing a 27-year-old woman with invasive trophoblastic hydatidiform mole metastatic to the lung. Gamma scintiscanning, using a polyclonal and monoclonal antibody specific to human chorionic gonadotropin, hCG, and labeled with Tc-99m, is described. The area of the primary lesion in the uterus was demonstrated with both antibodies tested without computer subtraction techniques; metastatic deposits in the lung were detected only with the aid of blood pool subtraction techniques.     

Detection of radiation-induced myocardial damage by technetium-99m sestamibi scintigraphy

A prospective study was initiated to assess the side-effects of postoperative adjuvant radiotherapy in patients with left-sided early breast cancer. Twelve patients with early breast cancer were examined before and a year after radiotherapy. Echocardiography, ECG and bicycle ergometry stress test with technetium-99m sestamibi myocardial perfusion scintigraphic were carried out to assess changes in regional myocardial blood flow. Six of the 12 patients had new fixed scintigraphic defects after radiotherapy (as compared with the preradiation examination). The localization of the defects corresponded well with the irradiated volume of the left ventricle. These defects were probably due to microvascular damage to the myocardium. Neither ECG changes nor left ventricular segmental wall motion abnormalities could be detected by echocardiography. To our knowledge this study is the first to show that radiation-induced microvascular damage to the myocardium may be detected by perfusion scintigraphy. This may limit the use of scintigraphy in diagnosing coronary artery disease in patients treated with thoracic radiotherapy. Long-term follow-up is necessary to assess whether the presence of microvascular damage is a prognostic sign for the development of radiation-induced coronary artery disease.     

Lymph kinetics with technetium-99m labeled radiopharmaceuticals. Animal studies

Aim of this study was to characterize suitable technetium-99m labeled tracers for lymphoscintigraphy by comparative animal tests. ANIMALS, METHODS: To evaluate the influence of the particle size and the organ tracer-uptake on lymphtransport animal experiments were performed on six different agents (including one control group). Activity distributions were examined in Sprague-Dawley-rats by lymphoscintigraphy; the maximum uptake (count-rate) of the whole body and in lymph nodes were analyzed by regions-of-interest-technique, respectively. Additionally, for characterization of lymphatic and extralymphatic traceruptake an intra-individual relative count-rate ratio of the liver, lung, kidneys, and spleen has been calculated following organ extraction. RESULTS: Organ specific differences of distribution were clearly demonstrated. Our results indicate that the kinetics of lymphoscintigraphic (99m)Tc-bound agents substantially depends on particle size. Reliable transport from the interstitium to initial lymph vessels and lymph node uptake suggested for tracers suited for lymphoscintigraphy a median size of about <100 nm. CONCLUSION: Our data could improve standardization of diagnostic methods and lead to an objective consideration of therapeutic procedures.     

Positive thyroid cancer scintigraphy using technetium-99m methoxyisobutylisonitrile

The aim of the study was to evaluate the possibility of detecting thyroid cancer recurrences without the need for withdrawal of thyroid suppressive treatment. Upper-body or whole-body scintigraphy was performed in a group of 200 patients evaluated for differentiated thyroid cancers in 1993 and 1994 using technetium-99m sestamibi. Scans were performed 20–30 min following i.v. administration of 500 MBq of^99mTc-methoxyisobutylisonitrile (MIBI). Bone and lung metastases were detected with very high sensitivity and specificity, with a very high predictive value of negative results and a somewhat lower predictive value of positive results. The sensitivity and specificity of findings in the neck were lower but the predictive value of negative results was high. Whole-body scans with^99mTc-MIBI are a useful tool in the follow-up of patients with differentiated thyroid cancer, for the detection of distant metastatic lesions.     

Evaluation of thyroid nodules with technetium-99m tetrofosmin dual-phase scintigraphy

Technetium-99m tetrofosmin, a lipophilic cationic complex molecule, was introduced for myocardial imaging. In some biodistribution studies it has also been reported to accumulate in the thyroid gland. Our objectives were to determine which thyroid nodules retain tetrofosmin and whether preoperative evaluation of malignancy is possible. Tetrofosmin scintigraphy was performed in 57 patients with a cold thyroid nodule on previously performed pertechnetate scintigraphy. All patients had undergone ultrasonography and sonographically guided fine-needle aspiration biopsy. The tetrofosmin scintigrams were obtained 5 min (early image) and 1 h (late image) after intravenous injection of 370 MBq. Only nodules that showed clear tracer retention after 1 h in comparison with retention at 5 min were classified as TETRO positive. Nodules without late retention were classified as TETRO negative. All patients underwent surgery and the histological results were compared with the results of tetrofosmin scintigraphy. Ten out of 11 patients with thyroid carcinoma (two pT1, three pT2, five pT4) were TETRO negative. One patient with papillary carcinoma (pT2) was TETRO positive. The mean nodular to thyroid tissue (N/T) ratio for the late scan was 1.0±0.20. There were 21 patients with thyroid adenomas (seven follicular, seven microfollicular and seven oxyphilic); 15 of these patients were TETRO positive and six TETRO negative. The mean N/T ratio for the late images was 1.34±0.41. All patients with degenerative goitre (24 cases) and the one patient with Hashimoto's disease were TETRO negative after 1 h and the N/T ratio was 0.92±0.12 on the late scan. Our results indicate that^99mTc-tetrofosmin scanning is of little value preoperatively in distinguishing thyroid carcinoma from other thyroid nodules. Tetrofosmin tends to demonstrate thyroid adenomas but does not have a routine role in the assessment of thyroid nodules.     

Comparison of technetium-99m sulfur colloid and technetium-99m albumin colloid labeled solid meals for gastric emptying studies

A Tc-99m albumin colloid (Tc-AC) kit has been introduced as an alternative to Tc-99m sulfur colloid (Tc-SC) for liver-spleen imaging. Since there is no need for boiling, the use of Tc-AC reduces preparation time and manipulation. Tc-SC is one of the most commonly used radiopharmaceuticals for the labeling of solid-phase markers in gastric emptying studies. In vitro studies were performed to evaluate the labeling efficiency and stability in hydrochloric acid and in human gastric juice of intracellularly labeled chicken liver and scrambled eggs labeled with Tc-SC and Tc-AC. Gastric emptying studies also were performed on 20 healthy volunteers with both Tc-SC and Tc-AC labeled scrambled egg sandwiches. There was no significant difference between Tc-SC and Tc-AC in the labeling efficiency of chicken liver (98% +/- 1% for Tc-SC, 96% +/- 2% for Tc-AC) and scrambled eggs (92% +/- 2% for Tc-SC, 91% +/- 3% for Tc-AC). However, both Tc-SC and Tc-AC labeled scrambled eggs showed a lower stability than chicken liver, particularly in human gastric juice. Gastric emptying curves from both meals in 20 normal subjects were also similar, with a mean half-emptying time of 85 +/- 13 minutes and 87 +/- 16 minutes for the meals containing Tc-SC and Tc-AC respectively. Tc-AC is a reliable alternative to Tc-SC as a radiotracer for solid-phase gastric emptying studies.     

Synthesis of technetium-99m labeled diaminodithiol for bifunctional chelating agents

Diaminodisulfide analogs (2a–b) were prepared by reduction of the intermediate Schiff's bases (1a–b) with sodium cyanoborohydride (NaBH₃CN) in dry diethyl ether under acidic condition without inducing internal cyclization reaction. The less sterically hindered NH proton of the diaminodisulfide (2b) could be successfully displaced by functional groups. The diaminodulfides (2a–b, 4c) were quickly converted to diaminodithiol (DADT; 5a–b, 6c) by reduction with a small amount of lithium aluminium in refluxing dry diethyl ether for 20 min, whereas reduction of bicyclic diaminodisulfides (3a–b) with excess LiAlH₄ did not produce the desired DADT (5a–b). Reduction of the other bicyclic diaminodisulfide including a functional group (methyl group) (3′c) with excess LiAlH₄ produced the DADT including a functional group in the sterically hindered nitrogen atom (8). Diaminodiathiol analogs including an N-functional group, such as N-p-iodophenethyl (6d), were synthesized without deiodination by a new revised procedure. The chelating ability of these ligands (5a–b, 6c–d, 8c) for Tc-99m was determined by thin-layer chromatography (TLC). The radiochemical yield of the Tc-99m labeled 5a–b, 6c–d, 8c was more than 95%. These results indicated that the DADTs including a functional group in the less sterically and the sterically nitrogen atom prepared by our new method have high chelating ability and high stability of Tc-99m and appear to be an attractive candidate as a useful chelator for bifunctional chelating agents.     

Rapid preparation method for technetium-99m bicisate

The method currently recommended for the preparation of technetium-99m bicisate (^99mTc-bicisate) requires a lenglhy 30-min incubation at room temperature. The purpose of thls study was to evaluate an alternative method to shorten the preparation time.^99mTc-bi-cisate was prepared with 3.7 GBq (100 mCi)^99mTc according to the manufacturer's instructions, except for the final incubation step, which was replaced with the microwave heating procedure. A standard thin-layer chromatography (TLC) method (i.e., Baker-Flex silica gel IB-F TLC plate with ethyl acetate as mobile phase) was used for the determination of the radiochemical purity (RCP) of^99mTc-bicisate. Our evaluation with different microwave heating processes (300 W with different heating times) demonstrated that as the microwave heating temperature was increased (i.e., 44°-71° C), an increased percentage of samples reached 95% within 5 min post preparation (n=58). The highest RCP value (i.e., 97.4%±0.5%,n=10) could be obtained immediately after an 8-s microwave heating time at 300 W (microwave temperature at 69° C), and an average RCP value of 96.4%±1.3% (n=90) was maintained throughout the 24-h evaluation period. However, the trend seemed to reverse at higher microwave temperatures (i.e., 76°-90° C), which reconfirmed our initial findings that overheating had no benefit for the preparation of^99mTc-bicisate. To ensure that temperature was the only determining factor, a hot water incubator sel at 69°C was used (n=6). Similar RCP results were achieved. In conclusion, the use of a microwave oven at a low heat cycle provides a rapid and efficient way to prepare^99mTc-bicisate.This work was presented at the 43rd Annual Meeting of the Society of Nuclear Medicine on 3 June 1996, and was published in abstract form (J Nucl Med 1996; 37: 142P–143P).     

Comparison of technetium-99m sulfur colloid and in vitro labeled technetium-99m RBCs in the detection of gastrointestinal bleeding

Twenty-seven paired Tc-99m sulfur colloid (SC) and Tc-99m RBC studies were evaluated for the detection of GI bleeding. The only two positive Tc-99m SC studies had positive early Tc-99m RBC studies as well. There were 15 other positive Tc-99m RBC studies (three during the first hour) and these were associated with normal Tc-99m SC scans. Approximately 70% of the positive Tc-99m RBC studies occurred after 1 hour. Tc-99m RBCs should be the initial test in patients with GI bleeding.     

Extensive gastric varices demonstrated by technetium-99m red blood cell scintigraphy

An alcohol abuse patient complicated by chronic pancreatitis had splenic vein thrombosis leading to gastric varices and underwent abdominal Tc-99m red blood cell scintigraphy. First pass study, sequential images up to 1 hour, and a 2.5 hour image showed abnormal radioactivity in the left side of the abdomen and midabdomen. In 24 hour images, the high level of activity in the left side persisted; in addition, there was accumulation of radioactivity in the cecum, ascending, transverse colon, the splenic flexure, and descending colon. A splenectomy was performed and during the surgical procedure, a large dilated vein in the greater omentum was noted. It is reemphasized that delayed imaging up to 24 hours is important when the results of earlier images are equivocal or negative.