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PubMed1993

Potential 99mTc radiopharmaceuticals for renal imaging: tris(N-substituted-3-hydroxy-2-methyl-4-pyridinonato)technetium(IV) cations.

A series of monocationic complexes of N-substituted-3-hydroxy-2-methyl-4-pyridinones labeled with technetium(IV)-99m have been evaluated in vivo as potential radiopharmaceuticals. The pyridinones have different substituents at the ring nitrogen atom: ethyl, i-propyl, i-butyl, benzyl, phenyl, p-methoxyphenyl, 3-butoxypropyl and cyclohexyl. Biodistribution studies of the 99mTc complexes have been carried out in rabbits and mice. High kidney uptake and retention of the radionuclide has been shown in rabbits and mice with the cationic complexes of 3-hydroxy-1-(p-methoxyphenyl)-2-methyl-4-pyridinone and 1-(cyclohexyl)-3-hydroxy-2-methyl-4-pyridinone. These 99mTcL3+ compounds appear to be morphologic renal agents.

Animals↗
PubMed1994

PEG-coated lipid vesicles with encapsulated technetium-99m as blood pool agents for nuclear medicine.

Unilamellar lipid vesicles of average diameter 200 nm containing 30 mM glutathione were internally labeled with 99mTc using exametazime (HMPAO) to transport technetium across the lipid bilayer. Vesicles were prepared both in the absence and presence of the lipid-polymer conjugate phosphatidylethanolamine-monomethoxy polyethylene glycol 5000 (PE-MPEG). Labeling efficiency both in the absence and presence of surface polymer was greater than 95% and the vesicles retained greater than 95% of their contents when incubated against 50% human serum at 37 degrees C for 12 h. When introduced intravenously into rabbits at a total lipid concentration of 4 mumol/kg (3.5 mg/kg), radiolabeled vesicles without surface polymer were rapidly cleared from the circulation with a half-life of approx. 30 min and delivered to liver and spleen, however if the lipid vesicles were prepared containing 3 or 4.5 mol percent PE-MPEG the circulation half-life of the label was approx. 5 and 10 h, respectively, and RES uptake was suppressed. These studies confirm a previous report of the utility of exametazime for preparing 99mTc-labeled lipid vesicles and demonstrate that extended circulation half-lives are achievable for 99mTc-labeled vesicles without recourse to high lipid doses and reticuloendothelial blockade. Applications to use exametazime as a blood pool marker in nuclear medicine are discussed.

Animals↗
PubMed1995

Synthesis, characterization and biodistribution of a new technetium-99m complex with trimethylsilylmethylisonitrile. Comparison with 99mTc-TBI and 99mTc-MIBI.

An isonitrile ligand with a silicium component was synthesized and a copper salt of this ligand was then used to form a 99mTc complex. We evaluated the physicochemical characteristics of the complex and its biodistribution in rat. The chemical properties, i.e. lipophilic affinity and charge, were comparable to those of other 99mTc complexes formed with similar isonitrile compounds (99mTc-MIBI and 99mTc-TBI). In contrast, the tissue biodistribution of this new technetium complex differed markedly, as it was mainly taken up in the liver and not at all in the heart.

Animals↗
PubMed1996

Technetium-99m radiolabeled ouabagenin-cysteine conjugate: biological evaluation in animal models.

Two ouabagenin-cysteine conjugates were synthesized by condensing 3-beta monochloroacetyl and 3-beta, 11-alpha dichloroacetyl ouabagenin with cysteine. The resulting ligands were radiolabeled with technetium-99m (99mTc) to furnish a single homogenous 99mTc chelate in each case with good stability. The animal experiments with these 99mTc-labeled conjugates established the superiority of guinea pig over rat and rabbit as an animal model, as previously observed for other tritiated or radioidinated cardiac glycosides or aglycones. In biodistribution experiments in guinea pig, these 99mTc chelates showed a favorable heart to liver (and other nontarget organ) uptake ratio, comparable to that of recently reported 125I-digoxigenin iodohistamine-3-oxime. The low heart to blood ratio in animal experiments with ouabagenin derivatives could be attributed to the absence of 3-beta sugar residues in these molecules, which is in agreement with the previous observation reported in connection with radioiodinated digoxin and digoxigenin derivatives.

Animals↗
PubMed1996

Radioimmunoscintigraphy using technetium-99m-labeled parental mouse and mouse-human chimeric antibodies to carcinoembryonic antigen in athymic nude mice bearing tumor.

Biodistribution and imaging characteristics of Tc-99m-labeled parental mouse and mouse-human chimeric antibodies to carcinoembryonic antigen (CEA), designated F11-39 and ChF11-39, respectively, were evaluated in athymic nude mice bearing the human CEA-producing gastric carcinoma (MKN-45) xenografts. Group F monoclonal antibodies such as F11-39 and ChF11-39 have been found to recognize the protein epitopes present on the domain B3 of the CEA molecule and to discriminate CEA in tumor tissues from the CEA-related antigens. The Tc-99m labeling was performed by immediately mixing a reduced antibody by 2-mercaptoethanol with Tc-99m pertechnetate in the presence of stannous chloride. The labeling yields of the two antibodies were greater than 95% when estimated using gel chromatography. Although these Tc-99m-labeled antibodies were stable in neutral saline solution, Tc-99m from both labeled antibodies was associated with cysteine solution. Technetium-99m ChF11-39 was more susceptible to transchelation than was Tc-99m F11-39. The immunoreactivity of each Tc-99m-labeled antibody was confirmed using MKN-45 cell-binding assay. Biodistribution studies in tumor-bearing mice were performed at 1 h, 5 h, and 20 h after being given IV injections of 3.7 MBq of either Tc-99m F11-39 or Tc-99m ChF11-39. All tumor-to-organ uptake ratios increased with time for both Tc-99m-labeled antibodies. Imaging results also showed selective and progressive accumulation of both Tc-99m antibodies at the tumor site. Both these Tc-99m-labeled antibodies have proved to be good radiotracers giving satisfactory scintigrams of the CEA-producing tumor.

Animals↗
PubMed2006

Left bundle-branch block artifact on single photon emission computed tomography with technetium Tc 99m (Tc-99m) agents: mechanisms and a method to decrease false-positive interpretations.

Myocardial perfusion scintigraphy is a well validated noninvasive method of evaluating for significant coronary artery disease, especially in cases where electrocardiographic changes are nondiagnostic, including left bundle-branch block. However, such testing with a technetium Tc 99m agent is often confounded by left ventricular septal-based false-positive perfusion defects. These defects can be either reversible or irreversible in the septal or anteroseptal wall, problematically then, in the territory supplied by the left anterior descending coronary artery. Mechanisms explaining false-positive defects include decreased perfusion via impaired microvessel flow and normal perfusion with apparent decrease in counts in a relatively thin septum (partial-volume effect). Key findings in myocardial perfusion images in the presence of left bundle-branch block that define true positives (ischemia) are reversible perfusion defects (especially at end diastole), a concomitant apical defect, and systolic dysfunction matching the perfusion defect.

Artifacts↗
PubMed2004

Comparison of the predictive value of exercise-induced ST depression versus exercise technetium-99m sestamibi single-photon emission computed tomographic imaging for detection of coronary artery disease in patients with left ventricular hypertrophy.

Scant knowledge exists regarding the significance of either additional ST depression in the presence of baseline depression or new stress-induced ST depression in patients with left ventricular (LV) hypertrophy. Accordingly, the purpose of this investigation is to determine whether the appearance and/or severity of ST abnormalities during exercise stress testing can accurately predict the prevalence of ischemic burden as measured by quantitative technetium-99m-sestamibi single-photon emission computed tomographic imaging in patients with LV hypertrophy. The results show that the presence of exercise ST-segment depression, as well as its magnitude, are not accurate predictors for identifying patients with coronary artery disease in the presence of electrocardiographic criteria for LV hypertrophy.

Adult↗
PubMed2005

Increasing age does not affect efficacy of sentinel lymph node biopsy using smaller-sized technetium-99m tin colloids for breast cancer patients.

BACKGROUND: Increasing age of breast cancer patients was reported to cause not only failure of sentinel lymph node (SLN) identification but also false negative results. METHODS: A retrospective review was conducted of breast cancer patients who underwent sentinel lymph node biopsy (SLNB) using small-sized technetium-99m-labeled tin colloid (particle size: 200-400 nm in diameter). A comparison between 82 patients who were less than 60 years and 40 patients who were > or =60 years of age was performed to evaluate the efficacy of SLNB using the small-sized tin colloid in older patients. RESULTS: One hundred twenty-two clinically node-negative breast cancer patients underwent SLNB. Apart from age, there were no statistically significant differences between the younger patients and the older patients in terms of the clinicopathologic characteristics. Successful mapping rates, false negative rates, and accuracy were comparable between the 2 groups. CONCLUSIONS: SLNB using the small-sized tin colloid was not affected by increasing age.

Adult↗
PubMed2006

Sentinel lymph node mapping with technetium-99m colloidal rhenium sulfide in patients with gastric carcinoma.

BACKGROUND: The objective of this study was to determine, with the use of technetium-99m colloidal rhenium sulfide, whether the concept of sentinel lymph nodes (SLNs) is applicable to gastric cancers. METHODS: Fifty-nine gastric cancer patients underwent radical gastrectomy and SLN mapping with an intraoperative hand-held gamma probe. After surgery, each transected lymph node was measured for radioisotope (RI) activities by a well-type scintillation counter. RESULTS: SLNs were detectable in 57 (96%) of 59 patients. The sensitivity, specificity, and diagnostic accuracy were calculated to be 83.3%, 100%, and 92.9%, respectively. Sensitivity was 100% in the T1 group, 91.6% in the T2 group, and 62.5% in the T3 group. When RI activities were measured with a well-type scintillation counter, every metastatic non-SLN was found to be situated in the same lymphatic basin as the SLNs. CONCLUSION: The SLN concept is applicable to patients with early gastric cancer (T1). SLN mapping is suitable for identifying the lymphatic basin in cases of gastric cancer.

Adenocarcinoma↗
PubMed2006

Intraoperative injection of technetium-99m sulfur colloid is effective in the detection of sentinel lymph nodes in breast cancer.

BACKGROUND: Our objective was to determine if intraoperative injection of technetium-99m-labeled sulfur colloid is as effective as preoperative injection in the detection of sentinel lymph nodes (SLNs). METHODS: Two hundred consecutive patients with breast cancer underwent SLN biopsy examination. Radiocolloid was injected in the preoperative area (group A) or immediately after induction of anesthesia in the operating room (group B). RESULTS: The SLN detection rate was similar for groups A (96%) and B (100%; P = .2). Radioactive SLNs were detected in 95% of patients in group A and in 97% of patients in group B (P = .1). The mean number of SLNs harvested was 1.6 and 2.1 for groups A and B, respectively. There was no significant difference in positive SLNs between groups (P = .11). CONCLUSIONS: Intraoperative injection of sulfur colloid is highly effective in the detection of SLNs, avoiding patient discomfort and surgical schedule delays.

Breast Neoplasms↗
PubMedDate not supplied

Technetium-99m-Sestamibi SPECT myocardial perfusion imaging in patients with complete left bundle branch block.

BACKGROUND: Diagnosis of coronary artery disease (CAD) in patients with left bundle branch block (LBBB) is considered a challenge in cardiology due to low accuracy of noninvasive methods such as basal and exercise stress test. Recently, myocardial perfusion imaging showed attainment of higher sensitivity and specificity. Scintigraphy with thallium-201 has been widely used in these patients. Few have used technetium-99m-Sestamibi and single photon emission computed tomography (SPECT). The aim of the study was to assess the diagnostic value of Tc-99m Sestamibi SPECT myocardial perfusion imaging in patients with complete LBBB. METHODS: We studied 57 consecutive patients with complete LBBB using Tc-99m-Sestamibi SPECT and treadmill or dipyridamole stress to evaluate CAD. Eighteen patients also underwent coronary angiography. Perfusion defects were classified as fixed or reversible. RESULTS: Prevalence of resting perfusion abnormalities in anterior, septal, and apical regions was 51, 56, and 19%, respectively. Sensitivity for detecting >50% left anterior descending artery (LAD) stenosis was 67 and 56% for anterior or septal defects, and 56% for specificity. Apical perfusion abnormality showed 21% sensitivity and 89% specificity. Among six patients with reversibility and who underwent coronary angiography, all had >50% LAD stenosis. CONCLUSIONS: With Tc-99m-MIBI SPECT imaging, prevalence of anteroseptal perfusion abnormalities was >50% in patients with LBBB. The test has moderate sensitivity and specificity for LAD disease. Absence of apical defect is specific for excluding LAD disease. Reversible changes in anteroseptal wall should be considered as an indicator of ischemia in this territory.

Age Factors↗
PubMed2006

Synthesis of a technetium-99m labeled tricyclic ganciclovir analog for non-invasive reporter gene expression imaging.

A potential radiopharmaceutical and HSV1-TK substrate, 3-((1,3-dihydroxypropan-2-yloxy)-methyl)-6-(4-(3-((2-mercaptoethyl)(2-(2-mercaptoethyl-amino)-ethyl)amino)propoxy)phenyl)-3H-imidazopurin-9(5H)-one-oxo-technetium(V), was synthesized via a converging approach and its chemical structure was comparatively characterized with a non-radioactive analog. The final radiochemical purity and yield were 97 and 73%, respectively.

Antimetabolites↗
PubMed2004

Physicochemical forms of technetium in surface water covering paddy and upland fields.

The behavior of an element in the environment depends on its physicochemical form. Basic data for the behavior of technetium in an agricultural environment were obtained by determining the physicochemical forms of Tc in 28 surface water samples from paddy and upland fields. Most of the (95m)Tc was present as TcO(4)(-) in the samples. The relative amount of this chemical form was 72% on average. A significant amount of insoluble Tc (particles more than 0.2 microm in size), however, was found in some samples. The maximum amount of the insoluble Tc was 91%. Other forms were found in insignificant amounts. The amount of insoluble Tc was relatively high in paddy soil samples. Paddy soils, gley soils and gray lowland soils were particularly effective in the insolubilization of Tc. Among the soil characteristics studied, cation exchange capacity, anion exchange capacity, and active aluminum showed significant correlations with the relative amount of insoluble Tc. When microorganisms were eliminated from the surface water samples before the addition of (95m)TcO(4)(-), little insoluble Tc was found, suggesting that microorganisms cause the physicochemical transformation. These results showed that the physicochemical form of Tc changes from TcO(4)(-) to insoluble forms in surface water covering paddy fields. The insoluble forms would restrict the mobility of Tc in paddy fields.

Fresh Water↗
PubMed2005

A comparison of concentration ratios for technetium and nutrient uptake by three plant species.

Technetium (Tc) is a non-essential element for which accumulation mechanisms in plants have recently been discussed, but only from the viewpoint of existence of anion transport proteins in plant cells. In this study, using three kinds of plants (Cucumis sativus L., Raphanus sativus L., and Brassica chinensis L.), uptake of Tc and Re (a chemical analogue of Tc) were observed. The results showed that Tc and Re uptake occurred not only with water mass flow or active nutrient uptake, but also with uptake of nutrient cations such as K+. It is suggested here that most stable chemical form under aerobic conditions, TcO4-, is used in cation transport as a substitute ions, such as Cl-. After TcO4- passes through a root surface, it moves through the xylem together with cations. Due to these uptake mechanisms, Tc is highly accumulated in plants.

Brassica↗
PubMed2005

Hepatic technetium Tc 99m-labeled sestamibi elimination rate and ABCB1 (MDR1) genotype as indicators of ABCB1 (P-glycoprotein) activity in patients with cancer.

BACKGROUND AND OBJECTIVE: The adenosine triphosphate-binding cassette transporter ABCB1 (P-glycoprotein) mediates terminal excretion of many chemotherapeutic agents, and variable ABCB1 activity may be an important contributor to interpatient variability in the clearance of chemotherapeutic agents. Our objective was to determine the elimination constant (kH) for hepatic elimination of technetium Tc 99m-labeled sestamibi (99mTc-MIBI) in patients with cancer and to compare this putative indicator of ABCB1 phenotype with clinical features and common ABCB1 genetic variants. METHODS: 99mTc-MIBI kH was determined from the time-dependent elimination profile of 99mTc-MIBI over a 90-minute hepatic scanning period in 66 patients with cancer. Single nucleotide polymorphisms (SNPs) in ABCB1 exons 12 (C1236T), 21 (G2677T/A), and 26 (C3435T) were documented by polymerase chain reaction-restriction fragment length polymorphism analysis. RESULTS: There was a 12-fold variation in 99mTc-MIBI kH across the cohort, which was not correlated with sex, age, conventional liver function test results, previous chemotherapy treatment, or history of liver metastasis. Mean 99mTc-MIBI kH was significantly reduced in patients with SNPs in exons 21 and 26 such that mean 99mTc-MIBI kH was 1.90 times (95% confidence interval, 1.14-2.66; P = .02) and 2.21 times (95% confidence interval, 1.47-2.97; P < .01) higher in subjects homozygous for the wild-type alleles than in those homozygous for these SNPs, respectively. CONCLUSION: Hepatic elimination of 99mTc-MIBI is a potential in vivo probe of hepatic ABCB1 activity that is significantly associated with the presence of common SNPs in ABCB1. 99mTc-MIBI hepatic scanning may provide a useful pretreatment indicator of ABCB1-mediated drug clearance in cancer patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

Value of technetium-99m diethyltriamine pentaaceticacid radioaerosol inhalation lung scintigraphy for the stage of amiodarone-induced pulmonary toxicity.

BACKGROUND: Amiodarone is a potent antiarrhythmic agent that is limited in clinical use by its adverse effects, including potentially life threatening amiodarone-induced pulmonary toxicity (AIPT). The alteration of technetium-99m diethyltriaminepentaaceticacid (Tc-99m DTPA) radioaerosol lung clearance in AIPT was experimentally investigated. METHODS: Eighteen white New Zealand rabbits (initial weight 4.1+/-0.2 kg) were divided into two groups. AIPT group (n=13) was administered amiodarone (20 mg/kg BW) ip as a 5% aqueous solution for 6 week. The controls (n=5) were administered the same amount of 0.9% saline ip. Four rabbits of AIPT group died due to AIPT. The reminders of AIPT group (n=9) and controls underwent Tc-99m DTPA radioaerosol lung scintigraphy at the end of the treatment period. AIPT group was divided into two subgroups according to histopathologic evaluation. AIPT-I had interstitial pneumonitis (n=4) and AIPT-II had interstitial pneumonitis with fibrosis (n=5). RESULTS: The mean T(1/2) values of in control, AIPT-I, and AIPT-II groups were found 54+/-4.4, 39.2+/-11.7 and 114.6+/-16.7 min, respectively. The mean T(1/2) values of Tc-99m DTPA significantly differ than other groups (X(2)=11.78, P=0.02). The significantly increased T(1/2) values was noted in AIPT-II group when compared with control (P=0.001). In contrast, AIPT-I group has significantly lower T(1/2) values than control group (P=0.03). CONCLUSION: We suggested that Tc-99m DTPA radioaerosol inhalation lung scintigraphy provides an accurate evaluation about stage of lung toxicity and therefore may be a useful tool for the monitoring of AIPT.

Aerosols↗
PubMed2005

Clinical correlation between increased lung to heart ratio of technetium-99m sestamibi and multivessel coronary artery disease.

BACKGROUND: An increased lung to heart ratio (LHR) on thallium-201 (Tl-201) stress myocardial perfusion imaging (MPI) is a predictor of adverse cardiac events and identifies people with extensive coronary artery disease (CAD). The implications of increased LHR in patients undergoing stress technetium-99m (tc-99m) sestamibi are developing. Our aim is to evaluate the relationship between increased LHR and extent of CAD in patients undergoing tc-99m sestamibi MPI. METHODS: We reviewed the records and images of 530 consecutive subjects who underwent exercise or adenosine tc-99 m sestamibi MPI. One hundred thirty-two had transient or partially reversible myocardial perfusion defects and 79 (exercise=34, adenosine=45, male=43, female=36, mean age=61 years) of these underwent coronary angiography (study population). The average LHR of these 79 subjects was compared to 79 patients (control population) with normal scans (exercise=50, adenosine=29, male=34, female=45, mean age=60 years). RESULTS: The mean LHR (+/-SE) in subjects with normal scans was 0.30+/-0.01. The mean LHR for those with abnormal scans and single vessel CAD who underwent exercise was 0.32+/-0.01 and pharmacological stress was 0.31+/-0.01. There was no statistically significant difference between the LHR of those with a normal scan and those with single vessel disease and an abnormal scan. However, there was a statistically significant association between the elevated LHR and multi-vessel CAD. The mean LHR for subjects with multi-vessel CAD with exercise was 0.39+/-0.01 (p=0.000) and for adenosine was 0.39+/-0.02 (p=0.000). CONCLUSION: An elevated LHR in patients undergoing exercise or pharmacological tc-99m MPI correlates with multi-vessel CAD.

Adenosine↗
PubMed2004

Labeling efficiency and biodistribution of Technetium-99m labeled nanoparticles: interference by colloidal tin oxide particles.

The interference of colloidal tin oxides on the biodistribution of (99m)Technetium radiolabeled chitosan nanoparticles has been overcome by using sodium borohydride instead of commonly used stannous salts as reducing agent for the reduction of (99m)Tc (VII) to lower valency states. Biodistribution of radiolabeled chitosan nanoparticles prepared by using stannous chloride method revealed localization of the radioactivity mainly in the liver and spleen while that of radiolabeled chitosan nanoparticles prepared by using sodium borohydride method manifested the presence of radioactivity in blood up to an extent of 10% even after 2 h. Interestingly, the reduction of radioactivity in the latter case with the progress of time was not manifested through an increase in activity in the liver. Rather, a time dependent increased accumulation of radioactive materials was observed in the stomach. From the results it has been concluded that the biodistribution is strongly influenced by the presence of colloidal particles of tin oxides and (99m)Tc labeled chitosan nanoparticles are RES evading and long circulating in blood when Tc (VII) is reduced by sodium borohydride and not by stannous chloride during radiolabeling process.

Animals↗