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PubMed1993

The role of iodine-131 and thallium-201 imaging and serum thyroglobulin in the management of differentiated thyroid carcinoma.

BACKGROUND: A prospective study was conducted to evaluate the use of iodine-131 sodium scintigraphy, thallium-201 chloride scintigraphy, and quantitative serum thyroglobulin estimation in the detection of differentiated thyroid carcinoma after thyroidectomy and iodine-131 sodium ablative therapy. METHODS: Thirty-one patients with a median age of 45.6 years (range, 20-73 years) were included in the study. After optimal endogenous thyroid-stimulating hormone stimulation (> 50 mU/ml), 53 pairs of iodine-131 and thallium-201 scans were performed. Concomitant serum thyroglobulin levels were available for 32 pairs of scans. The presence or absence of thyroid cancer was established by clinical, radiologic, and/or biopsy findings. RESULTS: The concordance between iodine-131 and thallium-201 scan findings in the presence of disease (25 scan sets) was 36%. The concordance in the absence of disease (28 scan sets) was 82%. Iodine-131 scanning was found to be significantly better (P < 0.05) than thallium-201 scanning, in terms of sensitivity (0.8 versus 0.6), specificity (0.96 versus 0.82), accuracy (0.89 versus 0.72), and the predictive value of a positive test (0.95 versus 0.75). The measurement of serum thyroglobulin had a low sensitivity (0.3) in the study but had a specificity of 1.0. CONCLUSION: It was concluded that iodine-131 sodium scintigraphy is superior to thallium-201 scintigraphy and serum thyroglobulin estimation for the detection of residual or metastatic differentiated thyroid carcinoma. However, the use of combined modalities provides a higher diagnostic yield. Thallium-201 scintigraphy was especially useful in cases in which iodine-131 scintigraphy was negative and quantitative thyroglobulin levels were elevated.

Adenocarcinoma↗
PubMed1981

Acute thallium poisoning: toxicological and morphological studies of the nervous system.

Nine days following ingestion of 5 to 10 gm of thallium nitrate, a young man died with severe cranial and peripheral neuropathy, anuria, and heart failure. Ultrastructural examination of nerves obtained on days 7 and 9 demonstrated axonal degeneration with secondary myelin loss. Axons were swollen and contained distended mitochondria and vacuoles. Thallium levels in more than twenty organs and body fluids ranged from below 1.0 to 178 microgram/gm; concentrations in twenty areas of the nervous system ranged from 29 to 140 microgram/gm. The highest brain levels of thallium were found in gray matter. In the thalamus, 87% of the thallium was present in cell sap. Tissue concentrations of thallium did not parallel those reported for potassium, suggesting that thallium distribution differs from potassium distribution in human beings.

Acute Disease↗
PubMed1980

Comparison of myocardial potassium and thallium flux as studied by tracer methods.

Although myocardial scintigraphy with 201thallium is widely applied in humans, the behavior of thallium at the cellular level is still under discussion. We compared the transmembrane fluxes of potassium and thallium in the isolated papillary muscle of guinea pigs. A qualitative conformity exists between potassium and thallium fluxes with respect to heart rate and temperature. Quantative comparison revealed a decreased flux rate of thallium for efflux when compared with potassium. The time dependence of thallium influx indicates that thallium scintigraphy of the myocardium reflects mainly an extracellular distribution.

Animals↗
PubMed1996

Prediction of in-hospital cardiac events using dipyridamole-thallium scintigraphy performed very early after acute myocardial infarction.

BACKGROUND AND HYPOTHESIS: Ischemic complications occur frequently during hospitalization after acute myocardial infarction. Dipyridamole-thallium scintigraphy performed early after admission can detect residual ischemia, may have additional prognostic value and be useful in the management of these patients. METHODS: Dipyridamole infusion and 201thallium imaging were performed on the third day of infarction in 114 consecutive patients. Coronary angiography was performed before hospital discharge in 90% of patients and exercise testing was performed at the time of discharge in patients without contraindications. RESULTS: Side effects occurred in 28 patients, but they were mild and transient or rapidly reversed with intravenous aminophylline. During hospitalization, three patients died and four had a nonfatal reinfarction. Patients with these major cardiac events had previously shown a higher prevalence of reversible perfusion defects during testing (71 vs. 31%, p < 0.05). In addition, 19 patients had early recurrent ischemia requiring early in-hospital revascularization. Overall, cardiac events defined as death, reinfarction, or early myocardial revascularization occurred in 22 patients. Of the patients with these events, 68% had thallium redistribution on initial myocardial scanning compared with 25% of patients without events (p = 0.0001). Patients with cardiac events also showed a higher number of myocardial segments with reversible perfusion defects (1.8 +/- 2.2 vs. 0.6 +/- 1.3, p = 0.001). Logistic regression analysis revealed that among all the other clinical, scintigraphic, and angiographic variables, the presence of thallium redistribution on the dipyridamole-thallium scan was the only independent predictor of cardiac events, increasing the risk by sixfold. Furthermore, during a 1-year follow-up, 14 other patients had ischemic events. Of these, 64% had previously shown thallium redistribution during early dipyridamole testing compared with 19% of patients without cardiac events (p < 0.001). CONCLUSIONS: Intravenous dipyridamole-thallium-scintigraphy performed very early after myocardial infarction is safe and useful to predict in-hospital ischemic events.

Aged↗
PubMed1985

Critical periods during development as assessed by thallium-induced inhibition of growth of embryonic chick tibiae in vitro.

In ovo application of thallium sulfate has been shown to produce a characteristic shortening and angulation of the tibia of the embryonic chick. The critical period for susceptibility to thallium-induced inhibition of tibial growth ends at 8 2/3 days of incubation, a time when the growth rate of the embryo declines by 55%. The aim of the present study was to expose tibiae to thallium in vitro to determine whether this response was intrinsic to the tibia. A 4-hour exposure to 400 micrograms thallium was found to be most effective. Growth of tibiae from 8-day-old embryos was inhibited, growth of tibiae from 9-day-old embryos was not, and the response of tibiae isolated from embryos of 8 2/3 days of incubation was intermediate. Therefore, the response of the tibia to thallium represents an intrinsic property and is not secondary to inhibited nerve growth as has been suggested. The critical period and its termination is also an intrinsic property of the tibia. Tibiae were exposed to thallium for 4 hours at various times after the tibiae had been established in vitro. Susceptibility to growth inhibition was shown to decline as tibiae developed beyond the critical period, a decline that could be correlated with a declining growth rate. Emphasis is placed upon critical events during development as a more useful concept than critical periods for explaining susceptibility to teratogens.

Age Factors↗
PubMed1982

Organ/tissue disposition of thallium in pregnant rats.

The placental transfer of thallium was studied in rats treated with a toxic dose of thallium sulphate (10 mg Tl/kg b.wt. p.o.), as well as in animals injected intraperitoneally with 201Tl-labelled thallium in amounts as low as 2 micrograms Tl/rat. Rapid uptake and retention of thallium in both maternal and fetal organs were observed. The administration of potassium ferrihexacyanoferrate II (100 mg/kg b.wt. twice daily by gavage) to rats acutely intoxicated with thallium on day 17 of pregnancy resulted in significant decrease of thallium concentrations in various maternal tissues including brain, in the placenta as well as in the fetal liver and brain. Potassium ferrihexacyanoferrate II also reduced the mortality of pregnant animals in the 72-h interval after the intoxication.

Animals↗
PubMed1993

Utility of thallium-201 and iodine-123 metaiodobenzylguanidine in the scintigraphic detection of neuroendocrine neoplasia.

Metaiodobenzylguanidine (MIBG) is a specific marker for neuroendocrine tumours, such as phaeochromocytoma, neuroblastoma, medullary thyroid cancer (MTC) and paraganglioma, but it suffers in some cases (especially in MTC) from a lack of sensitivity. Thallium is a well-known marker of cellularity with a great sensitivity and a lack of specificity. In order to determine whether the association of these two markers is able to improve the detection of neuroendocrine lesions, 137 scintigraphic examinations using MIBG and thallium were performed in 101 patients referred for suspicion or follow-up of neuroendocrine tumours. Thallium chloride was first injected (1 MBq/kg), images being acquired about 20 min after injection; 123I-MIBG (4 MBq/kg) was then injected and images acquired 5 and 24 h later. In patients with phaeochromocytoma or neuroblastoma, thallium scintigraphy appeared of little help since no tumoural site was discovered by thallium accumulation alone. In contrast, thallium examination seemed of interest in the detection of paraganglioma and MTC, the association of the two radiopharmaceuticals increasing the number of detected sites.

3-Iodobenzylguanidine↗
PubMed1986

Non-invasive investigation of lower limb revascularisation using resting thallium peripheral perfusion imaging.

Resting thallium thigh and calf imaging was performed in 11 patients with lower limb ischaemia before and after revascularisation. Eight patients had successful revascularisation but in the other three the procedure failed to improve the circulation. Despite symptomatic improvement and increases in ankle systolic pressures after successful revascularisation there was no change in thallium uptake. Thallium imaging was compared with radionuclide angiography and blood pool imaging in six patients. Radionuclide angiograms confirmed the presence of well developed collateral circulation in some patients with increased thallium uptake in the symptomatic limb and in all cases the angiograms were clinically useful. There was no correlation between thallium and blood pool images. Resting lower limb blood flow did not change after revascularisation and thallium peripheral perfusion imaging did not aid the assessment of the response to lower limb revascularisation.

Adult↗
PubMed1981

Movement of thallium (I) ions in vitro.

1. Movement of thallium (I) ions across the mucosal epithelium of descending rat colon, stripped of the muscularis externa in vitro was determined under voltage clamp conditions. 2. The unidirectional fluxes of thallium (I) ions from mucosal to serosal side (M leads to S) and in the opposite direction (S leads to M) were measured at 0 mV. A net flux of thallium (I) ions was observed from serosal to mucosal side (0.216 nmoles . cm-2 . h-1) in other words, the mucosal epithelium is apparently asymmetric for the movement of thallium (I) ions. 3. The investigations were carried out on the range of -30mV up to +30 mV from mucosal to serosal side. Thallium (I) ions move from mucosal to serosal side (M leads to S) by diffusion only (Pi = 0.119 cm.h-1), whereas into the opposite direction (S leads to M) thallium (I) ions in addition to a voltage-dependent component are transported against an electrical gradient.

Animals↗
PubMedDate not supplied

Lack of correlation after reperfusion between ventricular function and infarct size estimated by thallium single-photon emission computed tomography.

In 32 patients with acute myocardial infarction, who had undergone successful intracoronary thrombolysis, the results of regional wall motion measured from contrast cineangiograms 10 to 21 days after thrombolysis were related to the results of thallium single-photon emission computed tomography (SPECT) after intravenous dipyridamole. Wall motion was measured by means of the centerline method, and thallium defect size was estimated by comparing the patient's circumferential profile with that of 20 normals. No correlation was found between ejection fraction or regional wall motion and thallium defect size. The time from symptom onset to thrombolysis was inversely correlated with the degree of hypokinesis (r = -0.51) but not with thallium defect size. In patients treated within 3 hours, hypokinesis was significantly less than in patients treated later (-1.1 +/- 0.6 SD vs -2.2 +/- 0.8 SD, p less than 0.01) whereas thallium defect size was not significantly different in both groups. It is concluded that, in patients after thrombolysis, thallium defect size determined by SPECT does not reflect the degree of left ventricular dysfunction.

Adult↗
PubMed1996

Defect reversibility using thallium-201 reinjection. Comparison of stress-redistribution-reinjection with stress-immediate reinjection.

Immediate poststress thallium-201 reinjection followed by imaging one hour later has been proposed as an alternative reinjection protocol. This procedure is patient-convenient and time-saving as it shortens the investigation time to maximally 2.5 hours. The efficacy of the immediate thallium-201 reinjection protocol was assessed in 305 patients with stress perfusion defects in whom we compared the scintigraphic findings of 210 consecutive patients who underwent the standard thallium-201 stress/redistribution/reinjection protocol (Group I), with 95 consecutive patients who subsequently underwent the thallium-201 stress/immediate reinjection protocol (Group II). In all patients three-view planar images were visually and quantitatively analyzed. In Group I, defect reversibility was observed in 433 of 622 (70%) stress perfusion defects compared to 220 of 320 (69%) segments in Group II (p = NS). With respect to Q-wave related segments, defect reversibility was seen in 102 of 172 (59%) segments in Group I compared to 34 of 63 (54%) in Group II (p = NS). Based on defect reversibility, the diagnosis of myocardial ischemia was made in 184 of 210 (88%) patients Group I compared to 86 of 95 (91%) patients in Group II (p = NS). These findings indicate that immediate thallium-201 reinjection imaging provides at least similar data on defect reversibility as the standard thallium-201 stress/redistribution/reinjection approach. In practical terms, the stress/immediate reinjection approach seems advantageous as it reduces imaging time, enhances patient throughout and can be considered as one comprehensive imaging procedure.

Case-Control Studies↗
PubMedDate not supplied

Value of magnetic resonance imaging in patients with a recent myocardial infarction: comparison with planar thallium-201 scintigraphy.

The diagnostic accuracy of spin-echo Magnetic Resonance (MR) imaging in the detection and localization of a recent myocardial infarction (mean 4 days old) was compared to planar thallium-201 scintigraphy in 20 patients with a documented myocardial infarction. A control group of 10 subjects underwent a similar MR imaging procedure without thallium-201 scintigraphy. T1-weighted MR images (TE 30 msec) showed abnormal thinning of the infarcted left ventricular wall during systole (less than 50% of the opposite wall) in 11 patients (55%). On T2-weighted multi-echo MR images, (TE 30-60-90-120 msec) abnormally increased signal intensity was found in 17 patients and coincided with the location of the infarction. Thallium-201 scintigraphy detected the infarction in 18 patients. Comparison of T2-MR imaging and thallium-201 scintigraphy showed concordant findings in 82% of the left ventricular segments. In 9% of segments, thallium uptake was reduced with normal T2-MR and in 9% we found a normal thallium uptake with abnormal T2-MR findings. In all subjects of the control group, T1-MR images were normal, and only one subject showed increased signal intensity on T2-MR images. We conclude that the diagnostic accuracy of MR imaging in detecting a myocardial infarction is similar to that of T1-201 scintigraphy.

Female↗
PubMed2006

Removal of thallium by combining desferrioxamine and deferiprone chelators in rats.

The hypothesis that two known chelators deferiprone (1,2-dimethy1-3-hydroxypyrid-4-one, L1) and desferrioxamine (DFO) might be more efficient as combined treatment than as monotherapies in removing thallium from the body was tested in rats. Six-week-old male Wistar rats received chelators: L1 (p.o.), DFO (i.p.) or L1 + DFO as 110 or 220 mg/kg dose half an hour after a single i.p. administration of 8 mg Tl/kg body weight in the form of chloride. Serum thallium concentration, urinary thallium and iron excretions were determined by graphite furnace atomic absorption spectrometry. Both chelators were effective only at the higher dose level, while DFO was more effective than L1 in enhancing urinary thallium excretion, L1 was more effective than DFO in enhancing urinary iron excretion. In the combined treatment group, L1 did not increase the DFO effect on thallium and DFO did not increase the effect of L1 on iron elimination. Our results support the usefulness of this animal model for preliminary in vivo testing of thallium chelators. Urinary values were more useful because of the high variability of serum results. Result of combined chelators treatment should be confirmed in a different experimental model before extrapolation to other systems.

Animals↗
PubMed1981

Relationship of thallium-201 myocardial perfusion pattern to regional and global left ventricular function with exercise.

Thallium-201 redistribution pattern after exercise was related to rest and exercise left ventricular regional and global function, measured by radionuclide ventriculography, in 61 patients, 50 with coronary artery disease (CAD). Sixteen patients had exclusively transient thallium defects, suggesting ischemia: in this group, mean left ventricular ejection fraction (LVEF) was 65% at rest, falling to 58% during exercise (p less than 0.01). Eight patients had exclusively persistent thallium defects, suggesting scar: LVEF was unchanged during exercise, 58% to 59%. LVEF increased during exercise in the 17 patients without exercise thallium defects, seven with CAD: 66% to 73% (p less than 0.05). Individual LV wall segments which exhibited transient or persistent thallium defects contracted abnormally both at rest and during exercise; (2) both transient and persistent thallium defects can be associated with resting dyssynergy; and (3) in some CAD patients, apparent hypoperfusion does not necessarily predict left ventricular dysfunction during exercise.

Adult↗
PubMed1981

Thallium imaging in cardiac lymphoma.

A clinicopathologic correlation was made of thallium-201 myocardial perfusion imaging in two patients with massive myocardial invasion by malignant lymphoma. Despite extensive tumor involvement, the thallium scintigram was normal in one patient, while the other had only a modest-sized region of reduced tracer uptake. The discrepancy between the results of thallium scans and postmortem observations in these patients is probably related to uptake of thallium by tumor cells. The ability of any cellular and well-perfused tissue to absorb potassium, and potassium analogs such as thallium, suggest that thallium-201 scintigraphy may not be a useful method to screen for cardiac involvement in patients with known malignant neoplasms.

Adult↗
PubMed1984

Thallium scintigraphy during dobutamine infusion: nonexercise-dependent screening test for coronary disease.

Exercise thallium scintigraphy has proven to be a sensitive method for detecting coronary artery disease (CAD). However, early redistribution of thallium and inadequate exercise can reduce its sensitivity. In this study, dobutamine was infused in incremental doses (5, 10, 15, and 20 micrograms/kg/min) in 24 patients being evaluated for chest pain. Thallium scintigraphy was completed during the maximum dose of dobutamine tolerated and repeated 4 hours later. Significant CAD was present in 16 patients; the remaining eight had normal coronaries. Exercise ECG was obtained in 23 patients. During dobutamine thallium scintigraphy, reversible perfusion defects occurred in 15 of 16 CAD and in one of eight non-CAD patients, resulting in a sensitivity of 94% and a specificity of 87%. Exercise ECG had a sensitivity of 60% and a specificity of 63%. We conclude that: (1) dobutamine thallium scintigraphy appears to be a sensitive method for detecting significant CAD and provided a more sensitive screening test than exercise ECG; (2) dobutamine thallium scintigraphy is especially useful in patients who cannot exercise; and (3) because imaging occurs during dobutamine infusion, the problem of early redistribution may be mitigated.

Catecholamines↗
PubMed1989

Dipyridamole thallium-201 imaging pre- and post-coronary angioplasty for assessment of regional myocardial ischemia in humans.

To examine the effect of coronary angioplasty on myocardial perfusion and to examine anatomic correlates of dipyridamole-thallium images, we performed dipyridamole thallium scanning before and after 24 angioplasty procedures in 23 patients with clinical ischemia. Dipyridamole thallium tomography was performed 1 to 4 (mean +/- S.D. 1.5 +/- 0.9) days before and 1 to 25 (6.3 +/- 6.9) days after angioplasty. Coronary angioplasty was anatomically successful (less than 50% residual stenosis) in 23 of 24 patients. Before angioplasty, 3 of 24 scans were interpreted as normal, with no change in these patients following angioplasty. Prior to angioplasty, 19 scans showed redistribution. After successful coronary angioplasty in 18 of 19, 17 showed improvement in dipyridamole thallium scanning; one did not show improvement and later required repeat coronary dilatation. In one patient with failed angioplasty, images before and after angioplasty were unchanged. Nine scans showed "fixed" defects before angioplasty, with improvement in three of nine following angioplasty. Quantitative analysis of the dipyridamole thallium scans revealed significant improvement in uptake in the myocardial regions supplied by the successfully dilated artery (involved regions), but not in the remote (uninvolved) regions. We conclude that myocardial perfusion, as judged by dipyridamole thallium scanning, almost always improves following anatomically successful coronary angioplasty. "Fixed" defects may improve following angioplasty and presumably represent ischemia with incomplete redistribution, rather than infarction.

Adult↗
PubMed1991

Submaximal exercise thallium-201 SPECT for assessment of interventional therapy in patients with acute myocardial infarction.

Submaximal thallium-201 stress testing has been shown to provide important diagnostic and prognostic information in patients with acute myocardial infarction. The purpose of this investigation was to evaluate the diagnostic value of early submaximal stress testing and thallium-201 single photon emission computed tomography (SPECT) after interventional therapy. Scintigraphic results from 56 patients with infarctions, who underwent acute thrombolytic therapy, angioplasty, or both, were compared with late (6 weeks) functional outcome as assessed by radionuclide ventriculography and with results of discharge coronary angiography. A linear correlation was found between the extent of thallium-201 SPECT perfusion defect and late ventricular function (r = 0.74, p less than 0.01). Forty-two percent of patients with large SPECT perfusion defects had normal left ventricular ejection fractions, suggesting an overestimation of infarct size by early imaging. Sensitivity and specificity of thallium-201 SPECT for detection of coronary artery stenosis in noninfarct territories was 57% and 46%, respectively, indicating limited diagnostic definition of extent of underlying coronary artery disease. Results of follow-up coronary angiography showed a significant relationship between the size of the initial perfusion defect and early restenosis or reocclusion of the infarct artery. Thus the extent of early thallium-201 perfusion defects correlates with late functional outcome but appears to overestimate the degree of injury. Submaximal thallium-201 stress testing allows only limited characterization of underlying coronary artery disease. Early assessment of infarct size may identify a patient population at high risk for reocclusion of the infarct artery.

Adult↗