Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Thallium Radioisotopes”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

Modelling dual isotope parathyroid scans: objective decision making for tumour detection.

Parathyroid subtraction imaging using the radioisotopes thallium-201 and technetium-99m was first described in 1983. Since then it has become a routine method for the pre-operative localization of parathyroid tumours. Despite its widespread use, the interpretation of the subtraction images remains very subjective. This paper describes and evaluates an automatic objective method for the analysis of parathyroid scans. The method is based on the calculation of a likelihood ratio (the probability of obtaining a count in a given pixel if a tumour is present divided by the probability of obtaining that same count if a tumour is not present). The likelihood ratio is calculated for each pixel in a subtraction image. The calculated value is compared with a threshold. Pixels with likelihood ratios greater than the threshold are classified as belonging to tumour sites. Pixels with likelihood ratios less than, or equal to, the threshold are classified as belonging to 'no tumour' sites. The probability density functions required were obtained from computer simulated images. The likelihood ratio technique has a similar sensitivity and specificity to that of experienced human observers analysing computer simulated images. Furthermore, it is a completely automatic method which can provide the basis of a decision support system.

Computer Simulation↗

[Value of thallium-201 in the non-invasive evaluation of coronary cardiopathy].

Normal myocardial cells actively uptake the radioisotope Thallium-201 and its myocardial distribution is a reflection of the existent regional coronary artery blood flow at the moment of the examination. Thallium-201 reaches quickly a high intracellular concentration and then leaves myocardial cells in a mean time of 4 to 8 h. In the presence of significant coronary artery disease, uptake and elimination rates of Thallium-201 are delayed in ischemic tissue, compared to normal tissue. This leads to regional differences in relative concentrations which allow to identify viable areas with insufficient coronary flow in conditions of vasodilatation induced by exercise or pharmacologic means. This phenomenon does not occur in the irreversibly damaged myocardium, and affected areas fail to uptake the radioisotope. Clinical applications of this test are: 1.--Search for coronary artery disease. 2.--Assessment of patients with known coronary artery disease. 3.--Evaluation of patients after revascularization procedures. 4.--Assessment of coronary risk before peripheral vascular surgery. 5.--Detection of viable myocardium. 6.--Assessment of coronary reserve in patients with angor and normal coronary vessels.

Coronary Disease↗

Mechanism of high K+ and Tl+ uptake in cultured human glioma cells.

1. The aim of this study was to elucidate if the K+ uptake was higher in cultured human glioma cells than in cells from other malignant tumors and to analyze the importance of membrane potential and K+ channels for the uptake. 2. K+ transport properties were studied with the isotopes 42K and the K-analogue 201Tl. 3. Comparison with cultured cells from other malignant tumors showed that the specific steady-state accumulation of Tl+ was significantly higher in glioma cells (U-251MG and Tp-378MG). 4. In Ringer's solution at 37 degrees C the rates of K+ and Tl+ uptake were both inhibited by about 55% in ouabain and 60% in furosemide, bumetanide, or Na(+)- or Cl(-)-free medium. This indicated that the routes for K+ and Tl+ uptake were similar and due to Na,K-ATPase-dependent transport and to Na-K-Cl cotransport. 5. About 10% of the uptake was neither ouabain nor bumetanide sensitive. Ba2+, which is known to block inward-rectifying K+ channels and to depolarize glial cells, and other K+ channel blockers (Cs+ and bupivacaine), had no effect on Tl+ uptake. 6. Metabolic inhibition with dinitrophenol reduced the uptake rate to 17%. 7. The washout of Tl+ was unaffected by bumetanide and K+ channel blockers, but dinitrophenol caused a transient increase of 75%, an effect which persisted in the presence of K+ channel blockers. 8. It was concluded that the high specific K+ and Tl+ accumulation in cultured human glioma cells was due not to the presence of inwardly rectifying K+ channels or other identified K+ channels, but to Na,K-ATPase dependent transport and Na-K-Cl cotransport.

Barium↗

Beta skin dose determination using TLDs, Monte-Carlo calculations, and extrapolation chamber.

The beta doses produced by 90Sr-Y and 204 Tl beta sources were determined using three methods: Monte-Carlo calculations, measurements with TLDs, and measurements with an extrapolation chamber. Excellent agreement was obtained by all three methods, except a TLD nonlinear response to beta s was observed, which gives doses approximately 20% high for the 90Sr-Y source and 5% low for the 204Tl source. Also, analyses performed with low-energy beta s using these methods can determine errors in shield thickness covering TLD elements. Direct measurement of skin dose is not possible by the TLDs because the minimum shield thickness for the elements is 13 mg cm-2. A thinner shield for the elements must be used or the data must be extrapolated. Presently, thinner shields for TLD elements are not available, and the thick shields can lead to significant errors in skin dose when exposed to low-energy beta s.

Filtration↗

Daily intakes of 134Cs, 137Cs, 40K, 232Th, and 238U in Ukrainian adult males.

Total diet samples were collected to estimate dietary intakes of several radionuclides for Ukrainian males by duplicate portion studies. The samples were collected in the Kiev, Rovno and Volynsky regions in autumn of 1994. Some foodstuffs, including milk and potato, were also collected in the same regions. Daily intakes of 232Th and 238U were estimated to be 2.0 mBq and 7.5 mBq per person, respectively. The estimated daily intake of 40K, 85 Bq per person, was equivalent to that of Reference Man (the intake of a West European and a North American). Daily intakes of 137Cs were found to be quite different between some regions. Daily intakes were 1.8 Bq per person in the Kiev region and 12 Bq per person in the Rovno and Volynsky regions. Daily intake of 134Cs was below 1 Bq per person.

Adult↗

Significant mercury deposits in internal organs following the removal of dental amalgam, & development of pre-cancer on the gingiva and the sides of the tongue and their represented organs as a result of inadvertent exposure to strong curing light (used to solidify synthetic dental filling material) & effective treatment: a clinical case report, along with organ representation areas for each tooth.

Because of the reduced effectiveness of antibiotics against bacteria (e.g. Chlamydia trachomatis, alpha-Streptococcus, Borrelia burgdorferi, etc.) and viruses (e.g. Herpes Family Viruses) in the presence of mercury, as well as the fact that the 1st author has found that mercury exists in cancer and pre-cancer cell nuclei, the presence of dental amalgam (which contains about 50% mercury) in the human mouth is considered to be a potential hazard for the individual's health. In order to solve this problem, 3 amalgam fillings were removed from the teeth of the subject of this case study. In order to fill the newly created empty spaces in the teeth where the amalgams had formerly existed, a synthetic dental-filling substance was introduced and to solidify the synthetic substance, curing light (wavelength range reportedly between 400-520 nm) was radiated onto the substance in order to accelerate the solidifying process by photo-polymerization. In spite of considerable care not to inhale mercury vapor or swallow minute particles of dental amalgam during the process of removing it by drilling, mercury entered the body of the subject. Precautions such as the use of a rubber dam and strong air suction, as well as frequent water suctioning and washing of the mouth were insufficient. Significant deposits of mercury, previously non-existent, were found in the lungs, kidneys, endocrine organs, liver, and heart with abnormal low-voltage ECGs (similar to those recorded 1-3 weeks after i.v. injection of radioisotope Thallium-201 for Cardiac SPECT) in all the limb leads and V1 (but almost normal ECGs in the precordial leads V2-V6) the day after the procedures were performed. Enhanced mercury evaporation by increased temperature and microscopic amalgam particles created by drilling may have contributed to mercury entering the lungs and G.I. system and then the blood circulation, creating abnormal deposits of mercury in the organs named above. Such mercury contamination may then contribute to intractable infections or pre-cancer. However, these mercury deposits, which commonly occur in such cases, were successfully eliminated by the oral intake of 100 mg tablet of Chinese parsley (Cilantro) 4 times a day (for average weight adults) with a number of drug-uptake enhancement methods developed by the 1st author, including different stimulation methods on the accurate organ representation areas of the hands (which have been mapped using the Bi-Digital O-Ring Test), without injections of chelating agents. Ingestion of Chinese parsley, accompanied by drug-uptake enhancement methods, was initiated before the amalgam removal procedure and continued for about 2 to 3 weeks afterwards, and ECGs became almost normal. During the use of strong bluish curing light to create a photo-polymerization reaction to solidify the synthetic filling material, the adjacent gingiva and the side of the tongue were inadvertently exposed. This exposure to the strong bluish light was found to produce pre-cancerous conditions in the gingiva, the exposed areas of the tongue, as well as in the corresponding organs represented on those areas of the tongue, and abnormally increased enzyme levels in the liver. These abnormalities were also successfully reversed by the oral intake of a mixture of EPA with DHA and Chinese parsley, augmented by one of the non-invasive drug-uptake enhancement methods previously described by the 1st author, repeated 4 times each day for 2 weeks.

Body Burden↗

Non-invasive detection of reduced regional myocardial perfusion at rest in patients with unstable angina pectoris: increased regional 81mKr deposition following intravenous injection of 81Rb.

The present study was to investigate whether combined imaging of 81Rb and 81mKr distributions after i.v. injection of 81Rb at rest might improve the differentiation between ischemic and irreversibly damaged myocardium as compared to 201Tl scintigraphy at rest. In 21 patients who had undergone diagnostic cardiac catheterization for evaluation of chest pain, 148 MBq ultrapure 81Rb were injected i.v. at rest immediately following 201Tl scintigraphy at rest. Of 14 patients with earlier myocardial infarction, 10 patients revealed decreased regional tracer uptake of 81Rb and/or 81mKr, compared to 12 patients with regional 201Tl uptake abnormalities. In 3 patients with unstable angina pectoris, however, an evident mismatch between either the regional 201Tl or 81Rb distributions and the distribution of 81mKr was observed: in contrast to the reduced uptake of 201Tl and/or 81Rb, 81mKr activity was increased in 3 myocardial segments with normal left ventricular performance but supplied by coronary arteries with high-grade stenoses. In patients with contraindications to exercise tests (e.g. unstable angina) 81Rb/81mKr rest scintigraphy may therefore assist the differentiation between malperfused but potentially viable and irreversibly damaged myocardium.

Angina, Unstable↗

[Usefulness of exercise Tl-201 myocardial scintigraphy: comparison with positron emission tomography].

To evaluate the usefulness of exercise Tl-201 myocardial scintigraphy, we performed positron emission tomography and conventional exercise Tl-201 emission computed tomography (ECT) in 33 patients with old anterior myocardial infarction (Q-MI: 24, non Q-MI: 9). N-13 ammonia was used as a blood flow tracer, and imaging was performed at rest and after multistage, symptom-limited ergometer exercise. After the administration of F-18 deoxyglucose (FDG) at rest in the fasting state, metabolic imagings were performed to evaluate regional exogenous glucose utilization. Tl-ECT showed fixed defects in 19 of the 33 patients, redistribution of the tracer in nine and no defects in five. All patients having partial or complete redistribution on Tl-ECT showed exercise-induced ischemia on PET with N-13 ammonia and an increased uptake of FDG in the hypoperfused region, suggesting the presence of ischemic but potentially salvageable tissues. In addition, PET with N-13 ammonia detected periinfarct ischemia in nine of the 19 with fixed defects on Tl-ECT, and increased uptakes of FDG were observed in eight of the 19. These results indicate that Tl-ECT may underestimate myocardial viability in clinically infarcted regions. Further studies are needed to determine whether restoring coronary flow improves wall motion in regions with fixed defects on Tl-ECT.

Adult↗

Comparison of myocardial uptake of fluorine-18-fluorodeoxyglucose imaged with PET and SPECT in dyssynergic myocardium.

UNLABELLED: PET with 18F-fluorodeoxyglucose (FDG) can detect viable myocardium and predict functional recovery after revascularization. The use of PET for clinical routine, however, is limited. Recently, imaging FDG with SPECT was proposed. The aim of this study was to compare the diagnostic value of FDG-PET and FDG-SPECT in the detection of viable myocardium in segments with abnormal wall motion. METHODS: Twenty patients with previous myocardial infarction were studied. All underwent FDG-PET and FDG-SPECT during hyperinsulinemic glucose clamping. Regional perfusion was assessed with 13N-ammonia PET and early resting 201TI- SPECT. Regional wall motion was assessed with two-dimensional echocardiography. The agreement between FDG/13N-ammonia PET and FDG/201TISPECT to detect viability in dyssynergic myocardium was 76%. On a patient basis, PET and SPECT yielded comparable results in 17 of 20 patients. In a subgroup of patients with LVEF < or = 35% (n = 12), all PET and SPECT viability data were identical. CONCLUSION: This study shows a good correlation between the detection of viability in dyssynergic myocardium with FDG/13N-ammonia PET and FDG/201TI SPECT, both on a segmental and patient basis.

Ammonia↗

Gene therapy using antisense oligodeoxynucleotides labeled with Auger-emitting radionuclides.

Antisense oligomers may be used as a vehicle for carrying a radiation source into a specific location inside a tumor cell. The effects of radioactive-labeled oligodeoxynucleotides (ODNs) may have both direct antisense inhibition and radiation. Thus far, the use of radioactive ODNs has been limited mostly to clinical biokinetic studies. Therapeutic possibilities remain unknown if the basic question of the optimal source of radiation is unanswered. We have shown previously that oligonucleotide therapy can be effective theoretically with the internally labeled ODN phosphorothioates 32P, 33P, and 35S. Here, we expand the selection of radionuclides; we calculated in vivo subcellular tissue distribution for ODN phosphorothioates using the decay characteristics of several beta- and Auger-emitting radionuclides: 32P, 35S, 51Cr, 67Ga, 111In, (1114m)In, 123I, 125I, 131I, and 201Tl. The absorbed nuclear doses of these radiolabeled oligonucleotides were estimated in different cellular dimensions using the subcellular biodistribution data for two oligonucleotides (ISIS 2105 and ISIS 2922). Our results indicate that Auger-emitter isotopes do not give higher absorbed cell nuclear doses than the isotopes suitable for internal labeling of ODN phosphorothioates. However, the biological difference is difficult to estimate. The best isotope for subcellular targeting was 35S, which gives the smallest variation of nuclear dose in the different cell dimensions we studied (nuclear diameter, 6-16 microm; cellular diameter, 12-20 microm). Therefore, we conclude that in oligonucleotide radiotherapy, nuclear targets should be treated with short-range beta-emitters (35S or 33P) that are suitable for the internal labeling of oligonucleotides unless the relative biological effectiveness of Auger-emitters could be remarkably improved. Dual labeling with 32P and 35S may provide therapeutic benefits when treating smaller and larger targets simultaneously. Further in vivo development, especially with 33P and 35S labels for ODNs, is strongly indicated.

Chromium Radioisotopes↗

[Evaluation of myocardial ischemia in acute myocardial infarct by thallium scintigraphy and radioisotope angiography].

It is very important to evaluate the size of myocardial infarction and reversibility of ischemic myocardium in order to determine the severity and prognosis of patients with acute myocardial infarction. We performed thallium-201 redistribution myocardial scintigraphy and first pass radionuclide angiography in 12 patients with acute myocardial infarction. In eight cases, left ventricular wall motion was improved after nitroglycerin infusion (improved group), but in four cases it was unchanged (non-improved group). Six of the improved group showed a positive redistribution image, while in the non-improved group, no patient showed such an image. Ejection fraction increased after nitroglycerin infusion in the improved group, but unchanged in the non-improved group. There was no significant difference in hemodynamic parameters between the two groups at the time of admission, and after treatment hemodynamic parameters changed in the same way in both groups. In coronary angiography, three collateral channels were observed in the improved group, but none in the non-improved group. The severity of coronary artery stenosis in the two groups was almost identical. In eight patients, their regional ventricular wall motion improved after nitroglycerin administration, but there were four patients whose regional ventricular wall motion was unchanged. In both groups, hemodynamic and coronary angiographic findings were not different. But there were many positive redistribution images and collateral channels in the improved group. This result shows that reversible ischemia is indispensable for the improvement of regional wall motion. There was a case which showed a positive redistribution image on acute phase Tl-201 scintigraphy and a transient defect on the chronic phase exercise Tl-201 scintigraphy. But after the improvement of ischemia by aorto-coronary bypass operation, the defect on Tl-201 scintigraphy decreased and the wall motion improved. Neither redistribution on acute phase scintigraphy nor a transient defect on chronic phase exercise scintigraphy was observed in the non-improved group. From these data we conclude that the improvement of regional wall motion depends on reversible ischemia.

Adult↗

[Clinical usefulness of positron emission tomography (PET) in the evaluation of myocardial viability].

Positron emission tomography (PET) is a radionuclide imaging technique that allows quantitative assessment of regional myocardial function. It is mainly used in clinics to assess viability of dissynergic myocardium, by means of combined images of flow (with ammonia) and metabolism (with fluordeoxyglucose). The mismatch pattern, with an increase in fluordeoxyglucose metabolism in hypoperfused regions, is indicative of viability. The match pattern (a decrease in flow and metabolism in the same areas) is indicative of necrosis. Viability can also be assessed with water or fluordeoxyglucose independently quantified. Other promising methods are based in the study of oxygen consumption with 11C acetate and the study of hypoxia with 18F-misonidazole.

Coronary Disease↗