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PubMed1993

Do false positive thallium-201 scans lead to unnecessary catheterization? Outcome of patients with perfusion defects on quantitative planar thallium-201 scintigraphy.

OBJECTIVES: We postulated that artifactually abnormal thallium-201 scans are well identified at the time of initial clinical interpretation by experienced readers and do not lead to unnecessary coronary angiography. BACKGROUND: Exercise thallium-201 scintigraphy employing quantitative imaging techniques has yielded sensitivity and specificity values of 80% to 90%. There are image artifacts, such as breast shadows, and variants of normal that, if not correctly identified, can lead to a high false positive rate for detection of coronary artery disease. METHODS: Data from 338 consecutive patients with one or more focal thallium-201 defects on quantitative planar images were reviewed. All patients had undergone symptom-limited exercise scintigraphy and were classified as having either artifactual or nonartifactual thallium-201 defects after review of clinical reports. RESULTS: Of the 265 patients with defects judged to be nonartifactual on clinical readings, 167 underwent coronary angiography, which demonstrated significant coronary artery disease (> or = 50% stenosis) in 161 (96%) and normal findings in 6. Four of the latter six had documented prior myocardial infarction. The remaining 73 patients (85% female) had thallium-201 defects deemed to be artifactual on clinical readings, chiefly as a result of breast (66%) and diaphragmatic (8%) attenuation or variants of normal (26%). Only 4 (5%) of the 73 patients underwent subsequent coronary angiography; none had coronary artery disease. One had aortic stenosis and two had variant angina. Follow-up (mean 20 +/- 2 months) of the 69 patients in this group who did not undergo coronary angiography revealed no deaths and one nonfatal non-Q wave myocardial infarction. CONCLUSIONS: Artifactual defects on quantitative planar thallium-201 scintigraphy are well recognized by experienced interpreters and do not result in a high false positive rate leading to unnecessary cardiac catheterization. The incidence of coronary artery disease is high in patients with thallium-201 defects judged to be nonartifactual, and many patients with perfusion defects and angiographically normal coronary arteries have organic heart disease.

Aged↗
PubMed1975

Thallium-201 for myocardial imaging. Relation of thallium-201 to regional myocardial perfusion.

Following intravenous administration, the myocardial concentration of tracer thallium-201, potassium-43, and rubidium-81 were determined in mice; thallium was present in the greatest concentration in the myocardium (2.08% compared 1.25% for potassium and 1.15% for rubidium at 10 minutes). The regional myocardial distribution of thallium-201 was determined in dogs under conditions of normal flow, and total occlusion, and compared with potassium-43 (r=0.97). The regional distribution of thallium-201 was compared to microspheres under conditions of partial occlusion and reactive hyperemia (r=0.97). Thallium-201 was evaluated in a series of phantom scans, which demonstrated that the low energy X-ray of thallium was suitable for imaging. These results suggest that thallium-201 can be used for the evaluation of the distribution of regional myocardial perfusion.

Animals↗
PubMed1998

[Evaluation of myocardial viability using perfusion cardiac SPECT. 201-thallium rest/redistribution, 201-thallium rest/reinjection and technetium 99m tetrofosmin rest/postnitrates].

INTRODUCTION AND OBJECTIVES: It has been demonstrated that nitrate administration enhances the detection of myocardial viability in thallium-201 and technetium-99m sestamibi myocardial perfusion studies. The aim of this study was to assess the influence of nitrate administration on technetium-99m tetrofosmin myocardial uptake in patients with coronary artery disease and left ventricular dysfunction. PATIENTS AND METHODS: Twenty eight patients with coronary artery disease, previous myocardial infarction and left ventricular ejection fraction < 40% underwent, within 48 hours, rest/postnitroglycerin (0.4 mg sublingually) technetium-99m tetrofosmin single photon emission tomography (SPET), comparing these results with that of thallium-201 rest/redistribution SPET in 13 patients (first group) and with that of thallium-201 rest/reinjection SPET in the other 15 patients (second group). Tomograms based on the 3 spatial planes were divided into 15 segments and regional tracer uptake was quantitatively analysed. Viability was defined as presence of tracer uptake > or = 50% of peak activity. RESULTS: The percentage of peak activity at rest or after nitrate administration of technetium-99m tetrofosmin correlated, with that of thallium-201, at rest and after redistribution or reinjection (r = 0.8; p < 0.001). On resting technetium-99m tetrofosmin studies 167 of the 420 segments that were analysed had < 50% of peak activity. 14.5% of these segments showed reversibility after nitrate administration, with an increase in 99mTc-tetrofosmin uptake from 45 +/- 5% to 55 +/- 4% of peak activity (p = 0.001), in the first group, and from 40 +/- 9% to 57 +/- 9% of peak activity (p = 0.003), in the second group. Overall agreement between rest/postnitroglycerin technetium-99m tetrofosmin SPET studies and rest/redistribution or rest/reinjection thallium-201 SPET studies, regarding the presence of myocardial viability, was 87% and 90%, respectively. All except one reversible segments on tetrofosmin studies after nitrates had viability criteria on thallium studies. CONCLUSIONS: Nitrate administration at rest enhances the detection of myocardial viability using technetium-99m tetrofosmin SPET, correlating with viability criteria observed on thallium studies. It represents a simple and useful technique in the assessment of myocardial viability.

Aged↗
PubMed1977

Kinetic behavior of thallium in the rat. Accelerated elimination of thallium owing to treatment with potent diuretic agents.

1. In acute experiments anesthetized rats were treated with a subthreshold dose of 204Tl+, given intravenously in order to study the elimination kinetics of Tl+. Thallium disappeared from whole blood by means of two different half-lives (5 and 196 min, respectively), whereas VDbeta amounted to 1400 ml. The same kinetic parameters were found after chronic exposure to toxic amounts of Tl+. 2. After chronic exposure to thallium (10 or 30 ppm in the drinking water), the distribution of thallium over various organs proved non-specific. However, a pronounced accumulation was found in the renal medulla. 3. In view of the importance of the renal route in the elimination of Tl+ from the body and also because of the established accumulation of the toxic metal in the kidney, the influence of potent diuretic agents like furosemide and ethacrynic acid on the excretion of Tl+ was studied. The enhanced excretion of water and ions (Na+, K+, Cl-) was accompanied by a significantly accelerated excretion of thallium ions. High doses of ethacrynic acid (25 mg/kg) proved particularly powerful in this respect. Between the enhanced excretion of thallium and potassium ions a significant correlation was obvious, thus supporting the well-known similarity in the behaviour of these ions. The marked increase in renal elimination of thallium upon intensive diuretic treatment may be useful in the management of thallotoxicosis.

Animals↗
PubMed1987

Intracoronary thallium-201 scintigraphy after thrombolytic therapy for acute myocardial infarction compared with 10 and 100 day intravenous thallium-201 scintigraphy.

Thallium-201 imaging has been utilized to estimate myocardial salvage after thrombolytic therapy for acute myocardial infarction. However, results from recent animal studies have suggested that as a result of reactive hyperemia and delayed necrosis, thallium-201 imaging may overestimate myocardial salvage. To determine whether early overestimation of salvage occurs in humans, intracoronary thallium-201 scans 1 hour after thrombolytic therapy were compared with intravenous thallium-201 scans obtained approximately 10 and 100 days after myocardial infarction in 29 patients. In 10 patients with angiographic evidence of coronary reperfusion, immediate improvement in thallium defects and no interim clinical events, there was no change in imaging in the follow-up studies. Of nine patients with coronary reperfusion but no initial improvement of perfusion defects, none showed worsening of defects in the follow-up images. Six of these patients demonstrated subsequent improvement at either 10 or 100 days after infarction. Seven of 10 patients with neither early evidence of reperfusion nor improvement in perfusion defects had improvement of infarct-related perfusion defects, and none showed worsening. In conclusion, serial scanning at 10 and 100 days after infarction in patients with no subsequent clinical events showed no worsening of the perfusion image compared with images obtained in acute studies. Therefore, there is no evidence that thallium-201 imaging performed early in patients with acute myocardial infarction overestimates improvement.

Acute Disease↗
PubMed1987

Quantitative assessment of thallium myocardial washout rate: importance of peak heart rate and lung thallium uptake in defining normal values.

Traditionally, the results of exercise thallium scintigraphy were interpreted by transient defect analysis using initial and delayed images. Recently, washout rate analysis has been used for the relative quantification of exercise thallium scintigraphy. A diffuse slow washout from all myocardial regions has been defined as the indicator of extensive coronary artery disease. However, slow washout has occasionally been observed in normal cases and in healthy myocardial segments which are not supplied by a stenosed artery in patients with single or double vessel disease. We evaluate the factors influencing washout rate in 100 normal patients and 63 patients with angina pectoris (33 cases of single vessel disease and 30 cases of double vessel disease). The washout rates were calculated using circumferential profile analysis. In normal patients, washout rate was closely related to peak heart rate (r = 0.72) and inversely related to lung thallium uptake (r = -0.56). A diffuse slow washout was observed in seven (7%) of 100 normal patients, six (18%) of 33 cases of single vessel disease and eight (24%) of 30 cases of double vessel disease. The patients with diffuse slow washout showed significantly higher lung thallium uptake values and lower peak heart rates than those without diffuse slow washout (P less than 0.01). Thus, this false positive slow washout should be considered in the interpretation of quantitative exercise thallium scintigraphy.

Adult↗
PubMed1993

Factors affecting uniformity in interpretation of planar thallium-201 imaging in a multicenter trial. The Multicenter Study on Silent Myocardial Ischemia (MSSMI) Thallium-201 Investigators.

OBJECTIVES: This study was designed to assess factors affecting interobserver agreement in interpretation of planar thallium-201 stress imaging in the Multicenter Study on Silent Myocardial Ischemia (MSSMI). BACKGROUND: Five hundred fifty-six planar thallium-201 images were interpreted in 24 clinical centers and in a Radionuclide Core Laboratory. The trial's Coordinating and Data Center observed that the participating clinical centers interpreted a significantly greater number of thallium-201 stress studies as abnormal (i.e., myocardial ischemia or scar) than the Core Laboratory, and overall agreement was poor (kappa 0.27). METHODS: Agreement in image interpretation between clinical centers and the Radionuclide Core Laboratory was analyzed by kappa statistics. The reproducibility of the Core Laboratory results on 41 randomly selected test studies was excellent (kappa 0.77). In contrast, the reproducibility of interpretation in the clinical centers on their own studies was at best fair (kappa 0.45). It was hypothesized that the poor agreement and reproducibility in the clinical centers were caused by lack of standardization of image display and lack of objective criteria for image interpretation. To test the effect of standardization, 13 clinical investigators interpreted the same 41 test studies using 1) uniform image display, and 2) uniform quantification of images. RESULTS: The agreement in interpretation between clinical investigators and the Radionuclide Core Laboratory improved modestly with uniformity of image display (kappa 0.57) but improved markedly (kappa 0.66) with quantitative circumferential profile analysis. CONCLUSIONS: Lack of standardization in image display and lack of objective criteria for interpretation of thallium-201 images are responsible for suboptimal reproducibility and poor interlaboratory agreement in the interpretation of thallium-201 stress imaging. The adoption of a uniformly accepted method for computer quantification of myocardial perfusion images is crucial to improve agreement in interpretation.

Exercise Test↗
PubMedDate not supplied

Extraction separation of thallium (III) from thallium (I) with n-octylaniline.

A novel method is developed for the extraction separation of thallium(III) from salicylate medium with n-octylaniline dissolved in toluene as an extractant. The optimum conditions have been determined by making a critical study of weak acid concentration, extractant concentration, period of equilibration and effect of solvent on the equilibria. The thallium (III) from the pregnant organic phase is stripped with acetate buffer solution (pH 4.7) and determined complexometrically with EDTA. The method affords the sequential separation of thallium(III) from thallium(I) and also commonly associated metal ions such as Al(III), Ga(III), In(III), Fe(III), Bi(III), Sb(III) and Pb(II). It is used for analysis of synthetic mixtures of associated metal ions and alloys. The method is highly selective, simple and reproducible. The reaction takes place at room temperature and requires 15-20 min for extraction and determination of thallium(III).

Chelating Agents↗
PubMed1989

[Comparison of thallium perfusion and electrocardiographic findings at exercise thallium-201 scintigraphy with coronary arteriographic findings].

Findings of thallium-201 perfusion (Tl) and exercise electrocardiography (ECG) at exercise thallium-201 scintigraphy was compared with coronary arteriographic findings (CAG) in 283 patients. We classified these cases into four groups by Tl and ECG; [A] Tl(+).ECG(+), [B] Tl(+).ECG(-), [C] Tl(-).ECG(+), [D] Tl(-).ECG(-). Redistribution of thallium-201 was evaluated by qualitative (visual) analysis. Three percent of group A consisted of the patients with normal coronary artery, and thirty-eight percent of group D consisted of the patients with coronary artery disease. On exercise thallium-201 scintigraphic imagings, most of patients with normal coronary artery showed redistribution of inferior (24%) and septum (45%). On exercise electrocardiographic findings, most of patients with normal coronary artery showed ST-segment depression in II, III, aVF, V5 and V6. In patients with coronary artery disease, single vessel disease in group B was larger than that in group C (62% vs. 33%, p less than 0.05), and triple vessel disease and left main truncus disease in group C was larger than that in group B (37% vs. 10%, p less than 0.05). On exercise thallium-201 scintigraphic imagings, most of false negative in patients with coronary artery disease changed to true positive by quantitative analysis. The patients with less than 90% coronary stenosis in group C was larger than that in group B (65% vs. 100%).

Aged↗
PubMed1989

Thallium-201 myocardial scintigraphic evidence of ischemia in a patient with angina pectoris and normal coronary arteriogram: significance of thallium-201 washout analysis.

We present a patient who had anginal pain and an abnormal exercise electrocardiogram but a normal coronary arteriogram. We thought that myocardial ischemia was responsible for this symptom in view of the exercise left ventriculogram, exercise thallium-201 myocardial scintigraphy and effect of nitroglycerin on the anginal pain. The left ventriculogram at rest was normal but exercise worsened the entire left ventricular wall motion. Exercise thallium-201 myocardial images showed minimal reduction of radio-activity in the anterior, apical, antero-lateral and postero-lateral wall. Myocardial thallium-201 washout analysis revealed washout abnormalities all over the left ventricular myocardium similar to those of triple vessel disease, supporting the exercise left ventriculographic finding. Myocardial thallium-201 washout analysis as well as the visual method should be performed in patients with angina pectoris and normal coronary arteriograms.

Adult↗
PubMed1988

Reverse and pseudo redistribution of thallium-201 in healed myocardial infarction and normal and negative thallium-201 washout in ischemia due to background oversubtraction.

While the interpolative background subtraction used in quantitative planar thallium scanning can significantly overestimate the background overlying the heart, the effects of background oversubtraction on quantitative analysis have not been well defined. A mathematical model that relates myocardial washout determined using interpolative background subtraction to true myocardial washout is presented. The model was validated using phantoms and applied to myocardial and pulmonary thallium kinetic data in 100 patients, 85 with and 15 without coronary artery disease. The model showed that when using interpolative background subtraction, measured washout equals true washout in normally perfused myocardium; however, depending on the relation between myocardial and pulmonary thallium clearance, myocardial washout in ischemic regions and areas of infarction can be substantially over- or underestimated. Based on generally accepted quantitative criteria, this incorrect washout determination can at times lead to misdiagnosis of infarction as ischemia and ischemia as normally perfused tissue. It can also cause both "reverse redistribution" and "pseudo redistribution" of thallium in myocardial infarction in the absence of a physiologic basis.

Coronary Disease↗
PubMed1989

Thallium (I) interactions in biological fluids: a potentiometric investigation of thallium(I) complex equilibria with some sulphur-containing amino acids.

Formation constants for thallium(I) complexes of L-cysteine (CysH2), DL-penicillamine (PenH2), N-acetyl-L-cysteine (AcyH2), and N-acetyl-DL-penicillamine (ApeH2) in aqueous solution have been determined in 150 mmol dm-3 NaCl medium at 37 degrees C by potentiometric titrations using a glass electrode. Glycine has been used as a model for simple amino acids. The experimental data may be explained by the formation of the complexes T1(Cys)-, T1(Cys)H, T1(Pen)-, T1(Pen)H, T1(Acy)-, and T1(Ape)- with log formation constants 3.26, 11.28, 3.60, 12.05, 2.27, and 2.45, respectively. Analysis of the results obtained and comparison of thallium(I) complexing ability with that of dimethyl-thallium(III) seem to indicate that thallium(I) toxicity does not directly stem from its interference with the metabolism of sulphur-containing compounds.

Acetylcysteine↗
PubMed2004

Environmental concerns related to high thallium levels in soils and thallium uptake by plants in southwest Guizhou, China.

Thallium (Tl) contamination in soils poses a significant threat to human health due to the high toxicity of Tl and its ready assimilation by crops. This study is focused on high concentrations of Tl in soils in the Lanmuchang area of southwest Guizhou, China, which is related to natural processes of Tl-rich sulfide mineralization. Thallium contents range from 40 to 124 mg/kg in soils originating from the mining area, from 20 to 28 mg/kg in slope wash materials, from 14 to 62 mg/kg in alluvial deposits downstream, from 1.5 to 6.9 mg/kg in undisturbed natural soils and <0.2 to 0.5 mg/kg Tl in soils from the background area. These values indicate that both the erosion of natural soils from the Tl mineralized area and the mining activity are responsible for the distribution of high Tl concentrations in soils. Two other important toxic metals of interest, mercury and arsenic, also show high contents in soils, and are generally higher than Tl concentrations. Thallium concentration in plants exhibit species-dependent preferences. Thus, the enrichment of Tl in the edible parts of crop species decreases in the following order: green cabbage>carrot>chili>Chinese cabbage>rice>corn. The highest level of Tl in green cabbage is up to 500 mg/kg as dry wt., surpassing the values of Tl in the soils in which the green cabbages grow. In contrast, Hg and As are relatively less concentrated in local plants. The average daily uptake of Tl by the villagers of the Lanmuchang area through consumption of locally planted crops has been estimated to be 1.9 mg/person, which is 50 times the daily ingestion of individuals from the Tl-free background area. The daily ingestion of As and Hg from the study area are 0.03 and 0.01 mg, respectively. This indicates that Tl in the contaminated soils related to the natural Tl mineralization is being readily transferred to the human body through the food chain, and poses a significant threat to the health of the local villagers. Arsenic may pose a lesser health hazard, but mercury has an insignificant health risk. This study illustrates a real environmental concern related to land use and human health in areas containing high contents of Tl in soils associated with the natural occurrence of Tl-rich sulfides and coals, with or without mining activities. Thallium contamination in soils should be a critical parameter for proper land use and health related environmental planning and regulations.

Arsenic↗
PubMed1990

The safety of intravenous dipyridamole thallium myocardial perfusion imaging. Intravenous Dipyridamole Thallium Imaging Study Group.

Clinical data on 3,911 patients were collected from 64 individual investigators to evaluate the safety of intravenous dipyridamole-thallium imaging as an alternative to exercise thallium imaging for the evaluation of coronary artery disease. There were two deaths because of myocardial infarctions, two nonfatal myocardial infarctions, and six cases of acute bronchospasm. Chest pain occurred in 770 patients (19.7%). Headache and dizziness were reported by 476 patients (12.2%) and 460 patients (11.8%), respectively. ST-T changes on the electrocardiogram were seen in 292 patients (7.5%). Use of parenteral aminophylline to treat adverse events associated with intravenous dipyridamole brought complete relief of symptoms in 439 of 454 patients (96.7%). There is a potential for increased risk for serious ischemic events in patients with a history of unstable angina who are administered intravenous dipyridamole. In patients with acutely unstable angina (i.e., continuing chest pain) or in the acute phase of myocardial infarction, use of intravenous dipyridamole in thallium scintigraphy should be avoided. There is also an increased risk for bronchospasm in patients with a history of asthma; acute bronchospasm can be relieved immediately by administration of aminophylline. These results demonstrate that intravenous dipyridamole-thallium scintigraphy is a relatively safe, noninvasive technique for the evaluation of coronary artery disease.

Adult↗
PubMed1987

[Dipyridamole thallium-201 myocardial scintigraphy in coronary diagnosis; a comparison of methods with thallium-201 myocardial scintigraphy after ergometer stress].

Two scintigraphic methods, resting dipyridamole and exercise thallium-201 myocardial perfusion imaging, to detect and localize coronary artery stenosis were compared in 32 patients suffering from coronary artery disease. The sensitivity of detecting a greater than 50% coronary stenosis was 94% for exercise thallium-201 perfusion imaging and 88% for dipyridamole thallium-201 perfusion imaging. The overall sensitivity and specificity of localizing a greater than 50% coronary stenosis by the two methods were also not significantly different. The results of the two scintigraphic methods were independent of the severity of coronary artery disease. Dipyridamole thallium-201 myocardial perfusion imaging provides a useful and safe alternative test for detecting and localizing coronary artery stenosis in patients unable to perform maximal exercise.

Coronary Disease↗
PubMed1985

Thallium concentrations in body fluids and tissues in a fatal case of thallium poisoning.

A fatal case of thallium poisoning is described in which the thallium concentration was quantitated in plasma and urine during treatment and in tissue samples obtained on postmortem examination. As ileus paralyticus and the onset of renal failure were already manifested on admission of the patient, charcoal hemoperfusion and this technique in combination with hemodialysis were applied which showed to be tenfold more effective than the simultaneous renal elimination. The highest thallium concentration was found in the heart and not in kidneys as reported previously in animal experiments. Evidence is presented that thallium distribution in kidneys is dose dependent.

Adult↗
PubMed1993

[Are the results of thallium scintigraphy and coronary angiography equivalent? An evaluation of thallium scintigraphies performed at Vestfold Central Hospital].

The value of exercise-redistribution thallium-201 perfusion scintigraphy (SPECT; single photon emission computed tomography) in the diagnosis of coronary artery disease was evaluated in 23 patients (one patient tested twice) who were subsequently submitted to coronary angiography. Reversible perfusion defects indicating myocardial ischemia were found in 22 patients, of whom 18 had angiographically significant coronary artery stenoses. Two patients had negative thallium scans, one had a normal angiogram and one had single vessel disease. Thus 18 of 19 patients with angiographically verified coronary heart disease had a positive thallium scan. The majority of patients with left main stenosis and triple vessel disease had scintigraphic evidence of double or triple vessel disease. The scintigraphic method identified the correct anatomical localization in 73% of the angiographically verified coronary artery stenoses. In conclusion, a positive exercise-redistribution thallium scan had a high predictive value in the diagnosis of coronary artery disease, whereas its value in estimating the number and localization of stenoses was more limited.

Adult↗
PubMedDate not supplied

Effects of myocardial revascularization on regional thallium-201 uptake and systolic function in regions with reverse redistribution on tomographic thallium-201 imaging at rest in patients with chronic coronary artery disease.

OBJECTIVES: There is growing evidence that myocardial segments with reverse redistribution are viable in patients with chronic coronary artery disease. The aim of this study was to assess the effects of myocardial revascularization on systolic function and thallium-201 uptake in such segments. METHODS: Rest-redistribution thallium-201 tomography before and after myocardial revascularization was performed in 47 patients with chronic coronary artery disease. Regional function was evaluated by two-dimensional echocardiography before and after revascularization according to a 3-point scale (1 = normal, 2 = hypokinetic, 3 = a/dyskinetic). Improvement of dysfunctional segments was defined when systolic function score decreased > or =1 after revascularization. Reverse redistribution was defined as >8% decrease in relative thallium-201 uptake between rest and redistribution images. RESULTS: Reverse redistribution was found in 27 (57%) of 47 patients, corresponding to 60 (11%) of 564 myocardial segments. Of such segments, 24 (40%) had normal systolic function, 19 (32%) were hypokinetic, and 17 (28%) were a/dyskinetic. Thirty-six segments underwent myocardial revascularization, and reverse redistribution was no longer present in 86% of them subsequent to the procedure. Of 26 dyssynergic segments with reverse redistribution subjected to revascularization, 18 (69%) improved at follow-up. CONCLUSIONS: The findings of the present study indicate that reverse redistribution is a reversible phenomenon and is often associated with improvement of systolic function following revascularization in patients with chronic coronary artery disease.

Aged↗