Percent Thallium Research Articles

Study on the Solidification Process of Hgtl Amalgam at 30 at.% T

By means of a toroidal oscillating viscometer, logarithmic decrements of dampings have been measured in presence or absence of HgTl amalgam at 30 atomic percent thallium, at different temperatures, ranging from 12°C to 23°C.

Hg Amalgams are Homogeneous Compounds Having Liquid Metal Properties

By means of a toroidal oscillating viscometer, logarithmic decrements of dampings have been measured in presence of HgT1 amalgam at 28.1 atomic percent thallium, at different temperatures, ranging from 12,5°C to 17°C, with fluctuations every 0.25°C. In addition, the solidification process of Hgln amalgam has been investigated.

Prognostic value of exercise 201Tl tomography in patients treated with thrombolytic therapy during acute myocardial infarction.

Although myocardial perfusion scintigraphy is of proven value in the risk stratification of patients with a recent myocardial infarction who receive conventional therapy, its value in patients undergoing thrombolytic therapy remains controversial. Seventy-one patients who received thrombolytic therapy for acute myocardial infarction had exercise 201Tl tomography and coronary angiography before hospital discharge. Eleven (15%) of 71 patients had ischemic ST-segment depression during exercise, whereas 27 patients (38%) had scintigraphic ischemia. Twenty-five (37%) of 68 patients had a cardiac event consisting of either death (n = 2), recurrent myocardial infarction (n = 5), congestive heart failure (n = 7), or unstable angina (n = 11) during a follow-up of 26 +/- 18 months. Univariate predictors of cardiac events were as follows: Killip class (P = .04); left ventricular ejection fraction (P < .0005); total (P = .002) and ischemic (P < .0005) perfusion defect size; percent thallium lung uptake (P = .001); presence of infarct-zone redistribution (P = .02); and multivessel coronary artery disease (P = .01). By multivariate analysis, the significant joint predictors of risk were ejection fraction (P < .0005) and ischemic perfusion defect size (P = .005). The combination of ejection fraction and thallium tomography added significant incremental prognostic information to the clinical data, whereas angiography did not further improve a model that included clinical, ejection fraction, and tomographic variables. Quantitative exercise 201Tl tomography provides important incremental, long-term prognostic information in patients receiving thrombolytic therapy for acute myocardial infarction.

Head-to-head comparison of exercise-redistribution-reinjection thallium single-photon emission computed tomography and low dose dobutamine echocardiography for prediction of reversibility of chronic left ventricular ischemic dysfunction

We sought to directly compare the diagnostic value of exercise-redistribution-reinjection thallium single-photon emission computed tomography (SPECT) and low dose dobutamine echocardiography for prediction of contractile recovery after revascularization. Both thallium SPECT and dobutamine echocardiography have been proposed to predict the reversibility of left ventricular dysfunction after revascularization. Although both techniques permit differentiation of viable from nonviable myocardium, few studies have directly compared their accuracy in the same patients. Seventy-three consecutive patients (mean [+/- SD] age 59 +/- 9 years) with coronary disease and regional left ventricular dysfunction underwent exercise-redistribution-reinjection thallium SPECT and dobutamine echocardiography before revascularization. Recovery of function was evaluated with echocardiography 5.5 +/- 2.5 months after revascularization. For analysis, the left ventricle was divided into 16 segments, in which percent thallium uptake was quantitated using circumferential profiles, and regional wall motion was graded semiquantitatively (normal = 1; akinetic = 3). The diagnostic performance of the two tests was investigated both for individual patients and for individual segments. Individual patient analysis showed that left ventricular ejection fraction improved > 5% after revascularization in 43 patients, whereas 30 showed no change. Receiver operating characteristic curves were used to select optimal criteria for prediction of functional recovery after revascularization. According to a mean thallium uptake > 54% at reinjection, SPECT had a sensitivity of 72%, a specificity of 73% and an overall accuracy of 73%. Similarly, according to an improvement in wall motion score > 3.5 grades during doubutamine echocardiography, echocardiography had a sensitivity of 88%, a specificity of 77% and an overall accuracy of 84% (p = NS vs. thallium). Segmental analysis showed that SPECT and dobutamine echocardiography had similar sensitivity (77% and 75%, respectively), but SPECT had lower specificity (56% vs. 86%, p < 0.01). Quantitative exercise-redistribution-reinjection thallium SPECT and dobutamine echocardiography have comparable accuracy for prediction of reversibility of global left ventricular dysfunction after revascularization. However, dobutamine echocardiography has greater specificity than thallium imaging for prediction of functional recovery on a segmental basis.

Myocardial integrated ultrasonic backscatter in patients with old myocardial infarction: Comparison with radionuclide evaluation

The purpose of our study was to clarify whether the abnormalities in integrated backscatter may be used to assess myocardial viability in patients with old myocardial infarction by comparing these integrated backscatter parameters with conventional radionuclide and echocardiographic estimates of myocardial viability. Two myocardial integrated backscatter parameters, the magnitude of cyclic variation in integrated backscatter and the myocardial integrated backscatter calibrated with the power of Doppler signals from the blood along the same ultrasound beam (calibrated myocardial integrated backscatter), were measured in 21 normal persons and 33 patients with old anteroseptal myocardial infarction. Calibrated myocardial integrated backscatter was higher and the magnitude of cyclic variation in integrated backscatter was lower in the infarct septum compared with the septum of normal subjects. Percent thallium uptake, as assessed in scintigraphic images taken at rest or after reinjection, correlated well with the calibrated myocardial integrated backscatter ( r = −0.72, p<0.01) and more weakly but significantly with the magnitude of cyclic variation in integrated backscatter ( r = 0.55, p < 0.05) in 16 of 33 patients. The measurement of calibrated myocardial integrated backscatter, in addition to the magnitude of cyclic variation of integrated backscatter, may likely be valuable in the noninvasive assessment of myocardial viability.

Mechanism off exercise-induced hypotension in coronary artery disease

Hypotension during exercise testing has been considered a marker of extensive coronary artery disease (CAD) and poor prognosis. The mechanism of hypotension was examined in 25 CAD patients who developed hypotension during treadmill exercise testing (mean decrease in systolic blood pressure [BP] 33 ± 13 mm Hg) (group 1) and was compared with the results of 25 CAD patients who had a normal systolic BP response to exercise (mean Increase 53 ± 15 mm Hg) (group 2). The 2 groups were comparable in age, sex, extent of CAD, previous myocardial infarction, left ventricular ejection fraction, history of hypertension and cardiac medications. Exercise heart rate (121 ± 23 vs 133 ± 25 beats/min; p = not significant [NS]) and duration (6 ± 2 vs 7 ± 3 minutes; p = NS) were comparable. ST-segment depression occurred in 44% of patients in group 1 and in 52% in group 2 (p = NS), and angina during exercise occurred in 60% of both groups. Single-photon emission computed tomographic thallium images were abnormal in 24 patients (96%) in group 1 and in 20 patients (80%) in group 2 (p = NS). Percent thallium abnormality was 19 ± 12% in group 1, and 18 ± 14% in group 2 (p = NS), and the severity of thallium abnormality was 710 ± 510 in group 1, and 510 ± 500 in group 2 (p = NS). Ischemia involving the Inferior/posterior segments was seen in 68% of patients in group 1 and in 60% in group 2 (p = NS). Increased lung thallium uptake was seen in 48% of both groups. Thus, exercise-induced hypotension cannot be explained by the extent of CAD or ischemia; it is probably due to ischemic activation of mechanoreceptors, a mechanism similar to those of other types of neurally mediated hypotension.

Value of dipyridamole thallium-201 imaging in noninvasive differentiation of idiopathic dilated cardiomyopathy from coronary artery disease with left ventricular dysfunction

The purpose of this study was to noninvasively differentiate in patients with reduced global left ventricular function between those with idiopathic dilated cardiomyopathy (IDC) and coronary artery disease (CAD). Clinical features and findings of dipyridamole thallium-201 imaging in 55 consecutive patients with IDC were compared with those in 77 with CAD. Left ventricular ejection fraction was similar between the 2 groups (34 ± 16% vs 39 ± 7%). Patients with IDC had lower incidences of ischemic chest pain (11 vs 79%; p < 0.0001), electrocardiographs evidence of myocardial infarction (24 vs 82%; p < 0.0001), and reversible defects (4 vs 57%; p < 0.0001) than did those with CAD. The lowest percent thallium uptake in the initial imaging was less with CAD than IDC (30 ±15% vs 59 ± 10%; p < 0.001). Patterns of perfusion defects were classified as: no defects, multiple small defects and large defects. Of patients with IDC, 15 had no defects, 19 had multiple small defects, and 21 had large defects, whereas all those with CAD had large defects (p < 0.0001). Stepwise discriminant analysis, using chest pain and electrocardiography, revealed sensitivity of 89%, specificity of 87%, accuracy of 88%, and positive predictive value of 83% in the identification of patients with IDC. After including the findings of dipyridamole thallium imaging, analysis revealed that the combination of the lowest percent thallium uptake in the initial imaging, the chest pain, reversible defects, blood pressure at rest, pattern of perfusion defects and electrocardiography best identified (p < 0.0001) patients with IDC (sensitivity 95%, specificity 96%, accuracy 95% and positive predictive value 95%). These results indicate that the addition of dipyridamole thallium-201 imaging data to known clinical and electrocardiographic variables can help differentiate patients with cardiac dysfunction between IDC and CAD with a high degree of certainty.

Indications for Coronary Revascularization and the Postoperative Evaluations Using Thallium-201 Exercise Myocardial Scintigraphy and a Bull’s-Eye Display

Thallium-201 exercise myocardial scintigraphy and quantitative analysis using a bull’s-eye display were performed in 40 cardiac patients - 22 bypass and 18 percutaneous transluminal coronary angioplasty (PTCA) cases - to determine the indications for coronary artery bypass surgery and PTCA and to evaluate the degree of postoperative improvement. Regions of interest (ROIs) corresponding to each revascularized area were created on a bull’s-eye display, and the washout rate (WR) and percent thallium uptake were determined as percentages. Improvement was judged to have occurred if the revascularized coronary artery was patent and both the WR and percent uptake returned to the normal range determined from the examination of normal subjects. The results were as follows; (1) The preoperative mean WR of the improved areas (33 vessels) was 20 ± 15%, while that of the unimproved areas (17 vessels) was 33 ± 8%. We judged that an area was suitable for revascularization when the preoperative WR was less than 25 % which was the lower limit of the normal range. In this way 21 vessels were judged to be suitable for surgery, and a postoperative improvement was obtained in 18 areas. The areas considered to manifest a transient perfusion defect were those whose WR and percent uptake were less than normal, and these were considered the most preferable targets for revascularization. (2) In the 35 scintigraphically improved areas, 33 vessels were angiographically patent, while 7 vessels were obstructed on angiography in the 24 scintigraphically unimproved areas (the diagnostic validity was 68% of all 59 vessels). (3) The exercise tolerance increased significantly (p < 0.01) from 8.7 ± 1.7 to 11.5 ± 2.4 min in the improved cases in which all the treated areas improved after revascularization. There was no change in the exercise tolerance (before: 9.5 ± 2.6 min; after: 9.7 ± 3.5 min) in the unimproved cases in which none of the revascularized areas improved. We concluded that a myocardial region was suitable for revascularization when the preoperative WR and percent uptake were below the normal range. Since the scintigraphic evaluation accorded with the improvement in exercise tolerance and with patency on coronary angiography, the method seems useful for the postoperative follow-up.

Hg2TI is an Intermetallic Compound

Abstract By means of a toroidal oscillating viscometer, the shear viscosity of some mercury thallium alloys has been measured in the composition range 33–33.5 atomic percent thallium and over the temperature range from 13.5–16.5°C. Some discussion of the experimental results is given in terms of liquid coordination number.

Abnormal thallium kinetics in postoperative coarctation of the aorta: Evidence for diffuse hypertension-induced vascular pathology

After operative correction of congenital coarctation of the aorta, patients continue to have excess cardiovascular mortality, including manifestations of ischemic heart disease. Previous morphologic studies support the concept of direct hypertensive vascular injury in these patients. To determine whether abnormalities of myocardial perfusion were present in an asymptomatic group of patients with coarctation repair, 18 men and 9 women with a mean age of 26 years (range 19 to 41) were studied between 2 and 25 years after operative correction. Stress electrocardiography and quantitative thallium imaging by a circumferential profile technique were used. These patients were compared with a normal group, statistically defined as having a less than 1% prevalence of significant obstructive coronary artery disease. The postoperative coarctation group demonstrated a reduction in global thallium redistribution in each view analyzed. As compared with findings in the control subjects, thallium washout in the anterior view (41.9 versus 48.6%, p = 0.02) and left anterior oblique projection (40.5 versus 48.2%, p = 0.007) was significantly diminished. Although the postoperative coarctation group had a lower thallium redistribution rate in the lateral view (41.4 versus 46.3%, p = 0.09) this difference did not reach statistical significance because of the intrinsic variability of this projection. Plots of the median percent thallium washout revealed independence from circumferential profile angle, indicating global abnormalities in perfusion. No correlation between clinical variables and thallium kinetics could be established, suggesting marked individual variability in the development of this vascular lesion. The observation of abnormal thallium kinetics in patients with coarctation repair may have consequences for long-term follow-up and therapy.

Viscosity of Hg5Tl2at 14.5°C

Abstract By means of a toroidal oscillating viscometer, the shear viscosity of some mercury-thallium alloys has been measured in the composition range 28.5–29.5 atomic percent thallium and over the temperature range from 12.5–15.5°C. Some discussion of the experimental results is given in terms of liquid coordination number.

Far-Infrared Absorption in a Lead-Thallium Superconducting Alloy

Preliminary measurements have been made of the absorption of far-infrared radiation in the surface of a bulk superconducting alloy composed of lead with 10.0 atomic percent thallium at 1.4°K. The results indicate that the gap edge is quite distinct, in contrast to previous results of Richards and Tinkham on other alloys. The sharpness of the gap edge is thought to be characteristic of alloys which are homogeneous and have no trapped magnetic flux. Alloying narrows the observed gap width by about the same ratio as the critical temperature, and by an amount which is much smaller than that predicted by Suhl and Matthias from a simplified model. The subsidiary absorption maximum below the gap edge, which has been seen previously in pure lead, is also present in the alloy. This lends support to other evidence that itis not due to crystalline anisotropy.

Structure in the Thermoelectric Power of Dilute Indium-Lead Alloys

Liquid nitrogen and ice temperature measurements of the thermoelectric power of dilute indium-lead alloys indicate that there is detailed structure superimposed on the smooth trend of the data.Similar measurements are being made on the indium-thallium system to determine whether the structure is due to electronic or lattice effects. Those completed in the range of 4 to 9 atomic percent thallium indicate that the thermoelectric power varies linearly with composition in this interval. Hence it is presumed that the structure of the indium-lead data in this interval is of electronic origin.

Refraction and Dispersion of Thallium Bromide Iodide

The refractive indexes of a mixed crystal containing 45.7 mole percent thallium bromide and 54.3 mole percent thallium iodide were measured at three temperatures near 19, 25, and 31°C for wavelengths from 0.5770 to 39.38 μ. The data were fitted to Sellmeier dispersion equations and thermal coefficients of index were computed. Dispersion coefficients were determined at 25°. The results were compared with data on a similar crystal.

The Electrical Resistivity of Indium-Thallium Solid Solutions

Electrical resistivity measurements on indium-thallium solid solutions in the composition range from indium to 50 atom percent thallium and from the boiling point of helium to room temperature are described. An anomalous behavior of the resistivity of a specimen containing 30 atom percent thallium indicates that it probably undergoes a transformation from face-centered cubic to tetragonal in the temperature interval 45-60\ifmmode^\circ\else\textdegree\fi{}K.