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PubMed1978

The effect of Prussian blue and sodium-ethylenediaminetetraacetic acid on the faecal and urinary elimination of thallium by the dog.

After oral administration of sublethal doses of thallium (lower than 10 mg/kg) to dogs, 75.5 +/- 3.9 per cent of the dose was eliminated from the body--47 per cent faecal and 28 per cent urinary. Cumulative excretion reached 50 and 70 per cent after 10 and 25 days respectively, and was almost complete after 75 days. This was slightly lower at higher doses. The total body-burden of thallium, calculated from the cumulative excretion, decreased exponentially for at least the first 40 days with a half-time (T 1/2) of 6.5 days. Oral doses of Prussian blue after 10 days resulted in an acceleration of the thallium elimination from the body (T 1/2 2.5 days), an increase of the faecal (49 per cent) and a decrease of the urinary excretion (18 per cent). Nevertheless, the cumulative faecal and urinary thallium excretion was not influenced. Minor transitory influences of Prussian blue on the faecal thallium excretion could be observed up to day 26. After 40 days, Prussian blue could no longer influence the faecal thallium excretion. At no time did sodium-ethylenediaminetetraacetic (Na2EDTA) acid significantly change faecal or urinary thallium excretion.

Administration, Oral↗

PubMed1992

Disposition of oral dipyridamole in patients undergoing thallium 201 myocardial imaging.

Oral dipyridamole has been used in conjunction with thallium 201 imaging to diagnose coronary artery disease in patients unable to exercise. However, the pharmacokinetic disposition of high-dose dipyridamole, particularly the time to maximum drug concentration, has not been described in patients undergoing oral dipyridamole-thallium 201 scanning. Therefore, we measured serial concentrations in 20 outpatients undergoing thallium 201 testing after a single 400-mg oral dose of dipyridamole. In patients with positive thallium scans (group A), concentrations were slightly higher than in those with negative scans (group B). The variability in concentrations for both groups ranged from 3-118%. The area under the dipyridamole concentration-time curve from 0-4 hours ranged from 2.9-2.3 microgram.hr/ml. The time to peak plasma level for dipyridamole ranged from 0.5-2.5 hours, with two patients having undetectable levels at the time of thallium 201 injection. Dipyridamole concentrations did not correlate with changes in diastolic or systolic blood pressure, or heart rate. Although it is unknown what concentration is required to produce changes in coronary flow velocity, use of oral dipyridamole in this setting resulted in highly variable concentrations. In addition, these data suggest that a small percentage of patients will not have detectable concentrations at the time of the first thallium 201 scan, possibly limiting the usefulness of this agent in conjunction with thallium scintigraphy in some patients.

Administration, Oral↗

PubMed1991

A model to predict multivessel coronary artery disease from the exercise thallium-201 stress test.

PURPOSE: The aim of this study was to (1) determine whether nonimaging variables add to the diagnostic information available from exercise thallium-201 images for the detection of multivessel coronary artery disease; and (2) to develop a model based on the exercise thallium-201 stress test to predict the presence of multivessel disease. PATIENTS AND METHODS: The study populations included 383 patients referred to the University of Virginia and 325 patients referred to the Massachusetts General Hospital for evaluation of chest pain. All patients underwent both cardiac catheterization and exercise thallium-201 stress testing between 1978 and 1981. RESULTS: In the University of Virginia cohort, at each level of thallium-201 abnormality (no defects, one defect, more than one defect), ST depression and patient age added significantly in the detection of multivessel disease. Logistic regression analysis using data from these patients identified three independent predictors of multivessel disease: initial thallium-201 defects, ST depression, and age. A model was developed to predict multivessel disease based on these variables. As might be expected, the risk of multivessel disease predicted by the model was similar to that actually observed in the University of Virginia population. More importantly, however, the model was accurate in predicting the occurrence of multivessel disease in the unrelated population studied at the Massachusetts General Hospital. CONCLUSION: It is, therefore, concluded that (1) nonimaging variables (age and exercise-induced ST depression) add independent information to thallium-201 imaging data in the detection of multivessel disease; and (2) a model has been developed based on the exercise thallium-201 stress test that can accurately predict the probability of multivessel disease in other populations.

Arrhythmias, Cardiac↗

PubMed1990

[Value and limitations of stress thallium-201 scintigraphy in evaluating the viability of infarcted myocardial segments].

The aim of this study was to evaluate the value and limitations of stress thallium-201 scintigraphy in evaluating the viability of infarcted myocardial segments following percutaneous transluminal coronary angioplasty (PTCA) and aortocoronary bypass surgery. The relative thallium activity (RTA: the ratio of the count rate in the infarcted segment to that in the intact segment) obtained from delayed images of stress myocardial scintigraphy was used as an index of myocardial viability and was compared with the following parameters. 1) Thallium-201 myocardial perfusion images were made during transient coronary arterial occlusion (PTCA) in eight patients with old myocardial infarction. The RTA of delayed images after successful PTCA was compared with those of stress thallium-201 scintigraphy. There were no significant differences of the RTA between delayed images following PTCA and those of stress myocardial scintigraphy. We therefore, presumed that incomplete redistribution of the delayed images of stress thallium-201 scintigraphy did not truly reflect the degree of coronary stenosis. 2. Regional ejection fraction of the left ventricle after postextrasystolic potentiation (PESP) using equilibrium radionuclide ventriculography was studied in 18 patients with old myocardial infarction, and was compared with the RTA of delayed images of stress myocardial scintigraphy. A significant correlation was observed between the changes in regional ejection fraction by PESP and the RTA three hours after exercise. 3. The RTAs of early and delayed thallium-201 scintigrams were measured at rest in 30 patients with old myocardial infarction, and were compared with the RTA of delayed thallium 201 scintigrams after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗

PubMed1990

Thallium intoxication produces neurochemical alterations in rat brain.

Thallium, a rodenticide, has been shown to produce several neurological symptoms including motor weakness, ataxia, tremor, convulsion, coma and death. The present study was designed to evaluate the effects of acute or subacute exposure to thallium on several neurochemical biomarkers in rat brain. In the acute study, adult male CD rats were treated with 0 or 20 mg thallium/kg intraperitoneally (ip) and sacrificed 2, 6, or 24 hr after exposure. In the subacute study, animals were treated with 0 or 5 mg thallium/kg ip daily for 10 days and sacrificed 24 hr after the last dose. Acute injections of thallium produced in the frontal cortex significant increases in glutamine concentration after 6 hr and in taurine after 6 and 24 hr. In hippocampus, significant decreases in aspartic acid and taurine concentrations were found after 6 hr. Subacute exposure to thallium produced significant increases of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and serotonin (5-HT) in amygdala and increases in 5-HT concentration in hypothalamus. DA or muscarinic cholinergic (MCh) receptor binding did not show any significant alterations in caudate nucleus or frontal cortex after acute or subacute exposure to thallium. However, when membranes prepared from control caudate nuclei were incubated with thallium (1-100 microM) in vitro, we observed a dose-dependent decrease in DA and MCh receptor binding. These data suggest that the neurotoxicity produced by thallium exposure may be associated with changes in the concentrations of amino acids and other neurotransmitters in various regions of the rat brain.

Amino Acids↗

PubMed1990

Screening for a renovascular etiology in hypertensive patients undergoing myocardial scintigraphy: differential renal thallium-201 uptake.

In hypertensive patients with target organ damage the search for possible etiologic factors may be particularly relevant. To evaluate renal symmetry, differential renal uptake of thallium-201 was quantified on renal images at 30 mins to 3 h after tracer injection in 112 hypertensive patients undergoing myocardial perfusion scintigraphy for chest pain. In some patients, renal angiographic status was known at the time of thallium-201 scintigraphy (n = 10), or disease was highly suspected (failed angioplasty, n = 6); the remainder (n = 96) were 'screened' for renovascular disease by renal thallium-201 imaging; 32 normotensive patients with no history of renal disease served as controls. Validation of thallium-201 renal imaging was obtained in a total of 17 hypertensive patients who had correlating contrast angiography, confirming eight cases of unilateral or asymmetric bilateral renovascular disease. Renography with technetium-99m DTPA was performed in 28 patients; differential renal function according to this modality correlated well with differential renal uptake of thallium-201 (r = 0.98). Of the screened hypertensives, eight had marked asymmetry of differential renal uptake and eight had possibly significant asymmetry. Renal thallium-201 imaging provided the first evidence of asymmetric renal perfusion in four cases subsequently confirmed by abdominal angiography. In addition, four post angioplasty cases had persistent or progressive asymmetry of renal perfusion disclosed by this technique. Thus, ancillary renal imaging with thallium-201 can be used to identify hypertensive patients who should be considered for renal angiographic evaluation.

Heart↗

PubMed1989

Comparison of hypoxia and ouabain effects on the myocardial uptake kinetics of technetium-99m hexakis 2-methoxyisobutyl isonitrile and thallium-201.

Effects of hypoxia and ouabain on transcapillary exchange of [99mTc]hexakis (2-methoxyisobutylisonitrile) [SESTAMIBI, also known as MIBI or HEXAMIBI] and 201TI were investigated with indicator-dilution studies using isolated rabbit hearts. Peak myocardial extraction (Emax), permeability-surface area products (PScap), and net myocardial extraction (Enet) were compared among serial injections during constant coronary flows. Overall, measures of transcapillary transport (Emax and PScap) for SESTAMIBI were significantly lower (p less than 0.001) than those simultaneously determined for thallium, but estimates of tissue retention (Enet) for SESTAMIBI and thallium were not statistically distinguishable. Hypoxia had no significant effect on mean (+/- s.d.) Emax for SESTAMIBI (0.31 +/- 0.13) or thallium (0.59 +/- 0.11), nor on mean PScap or Enet values. Ouabain (1.5 X 10(-7) M and 1.5 X 10(-6) M) had no effect on SESTAMIBI or thallium Emax (respectively, 0.29 +/- 0.08 and 0.60 +/- 0.05) or on PScap for SESTAMIBI. Thallium PScap was depressed with higher ouabain dose (control, 1.22 +/- 0.40; high ouabain, 1.06 +/- 0.41 ml/min/g; p less than 0.01). Ouabain also caused a significant and progressive increase in average SESTAMIBI Enet (control, 0.23 +/- 0.10 to high ouabain, 0.33 +/- 0.12; p less than 0.05), but depressed thallium Enet (control, 0.38 +/- 0.14 to high ouabain, 0.32 +/- 0.18; p less than 0.01). These results suggest myocardial metabolic and/or functional status have minor influence on transcapillary transport of SESTAMIBI and thallium, but significantly affects cellular retention.

Animals↗

PubMed1987

SPECT thallium-201 scintigraphy for the detection of left-ventricular aneurysm.

We have noted that the presence of left ventricular anterior/apical aneurysm on contrast ventriculography or echocardiography correlates well with the finding of failure of convergence of the left ventricular walls toward the apex on single photon emission computed tomography (SPECT) thallium-201 images. To assess this observation, we analyzed the SPECT thallium scans of 74 sequential patients who had SPECT thallium scintigraphy and contrast ventriculography and/or echocardiography for evaluation of coronary artery disease. Immediate post-stress and 4-hr redistribution thallium-201 SPECT images, obtained following i.v. administration of 2 mCi of thallium-201, were reconstructed with no attenuation correction using three-dimensional linear and nonlinear filters and displayed in short, vertical-long, and horizontal-long axes. Of the 74 patients, contrast ventriculography and/or echocardiography showed anterior/apical aneurysms in 15 and a posterolateral aneurysm in one. SPECT thallium scans detected 14 of the 16 aneurysms, based on the criterion of failure of convergence of the ventricular walls toward the apex. There were two false-positives. Thus SPECT thallium-201 scintigraphy for the detection of left-ventricular aneurysm in this series had a sensitivity of 94%, a specificity of 97%, and an accuracy of 96%.

Adult↗

PubMed1986

Influence of peak exercise heart rate on normal thallium-201 myocardial clearance.

Measurement of myocardial clearance rates between initial and delayed images is a major justification for adding computer quantification to the interpretation of exercise 201TI images. To clarify the range of normal thallium clearance and its relationship to the level of exercise achieved, exercise thallium images in 89 normal subjects were analyzed: 45 asymptomatic subjects with less than 1% probability of coronary artery disease (CAD) (Group I), and 44 patients with chest pain found to have no significant CAD on angiography (Group II). Mean initial regional thallium uptake was similar in the two groups, but myocardial thallium clearance (mean +/- 1 s.d.) was slower in Group II, expressed as a longer half-life in the myocardium (8.2 +/- 7.6 hr compared with 3.4 +/- 0.7 hr p less than 0.001). Analysis of variance using ten clinical and exercise variables as covariates showed that the slower clearance in Group II was related to a lower peak exercise heart rate (HR) (154 +/- 27 compared with 183 +/- 11, respectively, p less than 0.001). By linear regression analysis, a decrease in peak HR of 1 beat/min was associated with a slower thallium clearance (longer half-life) of 0.05 hr. Using this formula, the clearance value in each patient was then corrected for peak exercise heart rate by decreasing measured clearance by 0.05 hr multiplied by the amount peak exercise heart rate which was below 183 (the mean value in Group I). There were no differences in the "corrected" clearance between the two groups. We conclude that thallium myocardial clearance after exercise is related in part to factors other than the presence of CAD, being slower when peak exercise HR is lower. Therefore, thallium clearance rates alone uncorrected for peak exercise heart rate should be used with caution when diagnosing CAD.

Adult↗

PubMed1996

Independent thallium-201 accumulation and fluorine-18-fluorodeoxyglucose metabolism in glioma.

UNLABELLED: SPECT with 201TI is an effective procedure for evaluating the malignancy of glioma. Our goal was to investigate the diagnostic relevance of both 201TI SPECT and [18F]fluorodeoxyglucose (FDG) PET and the relation between 201TI uptake and glucose metabolism in glioma using comparative SPECT and PET studies. METHODS: Thallium-201 SPECT and FDG dynamic PET studies were performed in 20 patients with untreated glioma (5 with glioblastoma, 5 with anaplastic glioma, 10 with low-grade glioma). Thallium-201 uptake in the tumor was estimated using the 201TI index, defined as the ratio of 201TI uptake in the tumor to that in the contralateral normal brain on SPECT images obtained 15 min after intravenous injection. We measured regional glucose metabolic parameters, including rate constants and regional cerebral metabolic rate of glucose utilization (rCMRgl), in the tumor. We then compared the regional 201TI index and glucose metabolic parameters with the histologic characteristics, malignancy and computed tomographic/ magnetic resonance imaging findings. In addition, we investigated the correlation between the 201TI index and glucose metabolic parameters. RESULTS: Thallium-201 SPECT showed abnormal 201TI uptake in all patients with glioblastoma and anaplastic glioma. Thallium-201 indices of glioblastoma (202.6 +/- 22.1%) and anaplastic glioma (176.6% +/- 26.6%) were significantly higher than that for low-grade glioma (106.7% +/- 13.8%). The rCMRgl value of glioblastoma (17.6 +/- 3.5 mumole/100 g/min) was also significantly higher than that for low-grade glioma (10.8 +/- 4.5 mumole/100 g/min), although rCMRgl showed a large variability in both high- and low-grade glioma. Rate constants of FDG kinetics had no correlation with histological grade of glioma. Some patients with high-grade glioma, however, showed false-negative results with FDG-PET because of high normal brain uptake of FDG. Conversely, most low-grade glioma could not be localized by 201TI SPECT. There was no correlation between the 201TI index and glucose metabolic parameters. CONCLUSION: Thallium-201 indices and rCMRgl values for glioblastoma were higher than those for low-grade glioma. Thallium-201 uptake in the tumor may be independent of increased glucose transport or metabolism. Thallium-201 SPECT and FDG-PET are complementary in the diagnosis of glioma, although 201TI SPECT is more significantly correlated with the malignancy of glioma.

Brain Neoplasms↗

PubMed1998

A safety study of thallium-containing ceramic superconductor material in rats.

Thallium is a highly toxic cumulative poison in humans and animals. The use of the metal as a component in ceramic superconductor material (CSM) raised concern about the health risk of CSM to children accidentally swallowing some of the CSM or to occupationally-exposed workers in the electronics industry. This study examined the biological availability of CSM by quantifying the thallium content in organs, blood and fecal matter of Sprague-Dawley rats after a single acute oral exposure to CSM and compares these values to similar thallium measurements from identical exposure to thallium sulfate. The CSM-exposed group had significantly less thallium than the thallium sulfate-exposed group in all tissues/fluids analyzed. This suggested that CSM poses a lower health risk to exposed persons than thallium sulfate.

Administration, Oral↗

PubMed1998

[Study of myocardial viability using single-photon emission computed tomography with 201-thallium and re-injection in 4 series (early and late images].

OBJECTIVE: The present study was designed to determine whether 24-hour imaging after thallium reinjection or imaging obtained shortly after reinjection provides better results regarding reversibility of fixed perfusion defects observed in conventional stress-redistribution imaging. PATIENTS AND METHODS: We studied 24 patients undergoing stress-redistribution thallium tomography with fixed defects (15 exercise, 6 adenosine, 3 dobutamine). All patients had coronary angiography and 17 a history of myocardial infarction. After obtaining the redistribution images, 1 mCi thallium was injected at rest, and images were acquired at 30 minutes and 24 hours after reinjection. The tomograms obtained were divided into 12 segments and analyzed quantitatively. RESULTS: Of the 190 abnormal segments on the stress images, 53 (28%) demonstrated improved thallium uptake on redistribution images and 137 had persistent defects. Shortly after reinjection, 33 (24%) segments had improved thallium uptake and 104 had persistent defects, 29 (28%) of which showed further improvement in the 24-hour study. In patients with myocardial infarction, of the 36 fixed severe defects, 9 (25%) had improved thallium uptake shortly after reinjection, increasing activity from 36 +/- 10% to 53 +/- 8%, and 22 (61%) defects improved at 24 hours, increasing activity from 37 +/- 8% to 56 +/- 6%. Therefore, 13 irreversible segments in the short-term study after reinjection were reversible on 24-hour images. CONCLUSION: These data indicate that 24-hour imaging after thallium reinjection provides better results regarding reversibility of fixed perfusion defects observed in conventional stress-redistribution imaging than imaging obtained shortly after reinjection.

Adult↗

PubMed1998

Relation between the kinetics of thallium-201 in myocardial scintigraphy and myocardial metabolism in patients with acute myocardial infarction.

OBJECTIVE: To investigate the relations between myocardial metabolism and the kinetics of thallium-201 in myocardial scintigraphy. METHODS: 46 patients within six weeks after the onset of acute myocardial infarction underwent resting myocardial dual isotope, single acquisition, single photon emission computed tomography (SPECT) using radioiodinated 15-iodophenyl 3-methyl pentadecaenoic acid (BMIPP) and thallium-201, exercise thallium-201 SPECT, and positron emission tomography (PET) using nitrogen-13 ammonia (NH3) and [F18]fluorodeoxyglucose (FDG) under fasting conditions. The left ventricle was divided into nine segments, and the severity of defects was assessed visually. RESULTS: In the resting SPECT, less BMIPP uptake than thallium-201 uptake was observed in all of 40 segments with reverse redistribution of thallium-201, and in 21 of 88 segments with a fixed defect of thallium-201 (p < 0.0001); and more FDG uptake than NH3 uptake (NH3-FDG mismatch) was observed in 35 of 40 segments with reverse redistribution and in 38 of 88 segments with fixed defect (p < 0.0001). Less BMIPP uptake in the resting SPECT was observed in 49 of 54 segments with slow stress redistribution in exercise SPECT, and in nine of 17 segments with rapid stress redistribution (p < 0.0005); NH3-FDG mismatch was observed in 42 of 54 segments with slow stress redistribution and in five of 17 segments with rapid stress redistribution (p < 0.0005). CONCLUSIONS: Thallium-201 myocardial scintigraphy provides information about not only myocardial perfusion and viability but also about myocardial metabolism in patients with acute myocardial infarction.

Adult↗

PubMed1998

[Dipyridamole-echocardiography and thallium exercise myocardial scintigraphy in the diagnosis of obstructive coronary or microvascular disease in hypertensive patients with left ventricular hypertrophy and angina].

BACKGROUND: Hypertensive patients with left ventricular hypertrophy can be affected with angina pectoris for significant epicardial coronary stenosis or microvascular disease with normal coronarography. Exercise-electrocardiography test is positive in both conditions. The aim of the present study was to assess the accuracy of dipyridamole-echocardiography test and thallium exercise myocardial scintigraphy in the diagnosis of epicardial coronary stenosis or microvascular disease in hypertensive patients with left ventricular hypertrophy and angina pectoris. METHODS: Forty-two hypertensive patients (22 males, age 40-76 years, mean 58.6 +/- 10.1), with left ventricular hypertrophy, typical angina pectoris, ischemia that can be induced by exercise-electrocardiography test, without previous myocardial infarction, myocardial revascularization or diabetes mellitus, underwent dipyridamole-echocardiography test, thallium exercise myocardial scintigraphy and coronarography. Dipyridamole-echocardiography test was performed with dipyridamole (0.56 mg/kg over 4 minutes, followed by 0.28 mg/kg from the 8th to the 10th minute) + atropine (1 mg from the 12th to 15th min.) and was positive for a transient dyssynergy of contraction of at least 2 myocardial segments; the left ventricle was divided into 16 segments. SPECT thallium myocardial scintigraphy was performed after bicycle exercise and then three hours later, and it was positive for reversible uptake defects of at least 2 segments with a 22-segment model. Coronarography was performed with Judkin's technique and was positive if at least one large epicardial vessel was narrowed by more than 50%. RESULTS: Coronarography: normal in 25 cases (59.5%, 8 males), pathologic in 17 (40.5%, 14 males): left main coronary artery in 1 (5.9%), three vessels in 5 (29.4%), two vessels in 3 (17.7%), 1 vessel in 8 (47%). Dipyridamole-echocardiography-test: positive in 15 cases (35.7%), negative in 27 (64.3%); sensitivity 88.2%, specificity 100%, diagnostic accuracy 95.2%, positive predictive value 100%, negative predictive value 92.6%. Thallium exercise myocardial scintigraphy: positive in 30 cases (71.4%), negative in 12 (28.6%); sensitivity 100%, specificity 48%, diagnostic accuracy 69%, positive predictive value 56.7%, negative predictive value 100%. CONCLUSIONS: Dipyridamole-echocardiography test has higher diagnostic accuracy and when positive, it predicts significant epicardial coronary stenosis. It can be less sensitive in one-vessel patients (2 false negatives were stenosis 75% of left anterior descending and 60% of 1st diagonal). Thallium exercise myocardial scintigraphy is complementary because when negative, it excludes epicardial coronary stenosis and confirms microvascular disease. In hypertensive patients with left ventricular hypertrophy and suspected angina pectoris, the following flow-chart may be proposed: the first test is exercise-electrocardiography test. Only those who are positive at low-to-intermediate workload then undergo dipyridamole-echocardiography test. Those who are positive in this then undergo coronarography, while the negative ones undergo thallium exercise myocardial scintigraphy. Those who are positive at thallium exercise myocardial scintigraphy perform the coronarography, while cases with negative results do not undergo further diagnostic tests since they are affected with microvascular disease.

Adult↗

PubMed2005

Thallium acetate induces C6 glioma cell apoptosis.

Thallium acetate is a known neurotoxic agent. In this study, we investigated the mechanisms by which thallium acetate induces cell cycle arrest and cell apoptosis in cultured LC6 glioma cells. Exposure of C6 glioma cells to thallium acetate decreased cell viability as demonstrated by the MTT assay. Incubation of thallium acetate arrested cell cycle progression at the G2/M phase and caused cellular apoptosis at 300 microM as determined by trypan blue exclusion and flow cytometric analysis. The G2/M arrest was associated with a decrease in expression of CDK2 protein and an upregulation of p53 and the CDK inhibitor p21(Cip1), but not p27(Kip1). Thallium acetate did not alter the protein levels of cyclin A and B; cyclin D1, D2, and D3; and CDK4 expression in C6 glioma cells. Incubation of C6 glioma cells with thallium acetate upregulated the expression of proapoptotic proteins Bad and Apaf and downregulated the expression of anti-apoptotic proteins Bcl-xL and Bcl-2. In conclusion, these data suggest that thallium acetate inhibits cell cycle progression at G2/M phase by suppressing CDK activity through the p53-mediated induction of the CDK inhibitor p21(Cip1). Impairment of cell cycle progression may trigger the activation of a mitochondrial pathway and shifts the balance in the Bcl-2 family toward the proapoptotic members, promoting the formation of the apoptosome and, consequently, apoptosis.

Animals↗

PubMed2001

Extraction separation and electrothermal atomic absorption spectrometric determination of thallium in some sulfide minerals.

A method for thallium determination in some sulfide minerals (sphalerite, galena, orpiment and realgar) by electrothermal atomic absorption spectrometry has been proposed. Mineral samples were dissolved in a mixture of HNO3 and HCl. The effect of interfering elements (Zn, Pb and As) on the determination of Tl in the investigated minerals was studied. These investigations show that it is not possible to determine thallium directly from solutions obtained by dissolution of minerals in mineral acids, because these matrix elements tend to decrease the absorbance of thallium. Also, it was found that the investigated minerals contain iron that tends to increase the absorbance of thallium. Therefore, a method for extraction of thallium with isoamyl acetate from 10 mol/l HCl media was proposed. In these conditions, Zn, Pb and As remain in the inorganic phase, but iron and thallium are extracted into organic phase. Reextraction of iron from the organic layer was performed with 4 mol/l H2SO4. The determination of thallium was performed in the organic phase using Pd as modifier. The investigated sulfide minerals originated from different mines from the Republic of Macedonia. The relative standard-deviation range was between 2.20 to 3.92%. The detection limit of the method (calculated as 3SD of the blank) was found to be 0.05 microg/g.

Journal Article↗

PubMed1997

Delayed positive thallium uptake in large B-cell non-Hodgkin's malignant lymphoma.

We report an unusual finding in an AIDS patient who presented with a large mediastinal mass and multiple lymphadenopathy. A sequential thallium and gallium scan to specify the nature of the mediastinal mass was requested. The early thallium images, acquired 15 min after the intravenous injection, showed no uptake in the mass. The delayed images 2 hr later showed intense thallium uptake. A gallium scan performed 48 hr later also showed intense gallium uptake in the mediastinal mass. Biopsy from the inguinal lymph node confirmed the presence of large-cell diffuse noncleaved malignant lymphoma. This case raises questions about the optimum time of imaging for thallium in high-grade lymphoma, whether delayed imaging is essential, about previous reports of low sensitivity of thallium in undifferentiated lymphoma and about the mechanism of thallium uptake in this type of tumor.

Citrates↗

PubMed1990

Cardiac risk in vascular surgery. The oral dipyridamole-thallium stress test.

The value of the oral dipyridamole-thallium stress test in identifying patients at high risk of myocardial infarction after vascular procedures has not been documented. We studied prospectively 46 patients who underwent an oral dipyridamole-thallium stress test before undergoing vascular operations. Twenty patients (43%) had a positive test result, defined by a thallium defect with reperfusion, while 26 patients had a negative test result. Myocardial infarctions were documented postoperatively in 5 (25%) of 20 of the group with positive results and 1 (4%) of 26 of the group with negative results. Three of the six myocardial infarctions were clinical; all three were in the group with positive results. No correlation was identified between dipyridamole-thallium stress test results and clinical cardiac history. A positive dipyridamole-thallium stress test result is a more sensitive predictor of postoperative myocardial infarction than ejection fraction or history of coronary artery disease. The oral dipyridamole-thallium stress test is as useful as the intravenous test in this setting.

Administration, Oral↗