Tl-201 Studies Research Articles

The prognosis of a normal Tl-201 stress-only SPECT MPI study

BackgroundStress-only Tc-99m SPECT myocardial perfusion imaging (MPI) decreases test time and patient radiation exposure with a proven benign prognosis of a normal study. The imaging sequence of Tl-201 MPI always starts with the stress portion; therefore, no pre-test decisions are needed regarding the imaging sequence. The recent intermittent Tc-99m shortage afforded the unique opportunity to study an unselected group of patients undergoing Tl-201 imaging. MethodsWe retrospectively reviewed all the patients who had SPECT MPI with Tc-99m or Tl-201 over a 1-year period. When Tc-99m was not available, patients received Tl-201. All stress Tl-201 images were routinely processed, and if normal, rest imaging was not done. When Tc-99m was used, patients with lower pre-test probability were selected for a stress-first protocol. We compared the all-cause mortality of patients with normal Tl-201 studies to those with normal stress-only and rest-stress Tc-99m studies using the Social Security Death Index. Unadjusted and risk-adjusted survival analysis was performed. Specific causes of death (cardiac or non-cardiac) were determined by medical record review and contact with treating physicians. ResultsA total of 3,658 patients underwent stress MPI during this time period. Of the 1,215 patients who had Tl-201 MPI, 716 (67%) had a normal stress-only study. Out of 2,443 patients who underwent Tc-99m MPI, 70% had normal perfusion with 1,098 normal stress-only studies and 493 normal rest-stress studies. The average follow-up was 23.3 ± 5.3 months. Unadjusted all-cause mortality at the end of follow-up was 7.1% in the Tl-201 stress-only group, 6.3% for Tc-99m stress-only patients, and 4.3% in the Tc-99m rest-stress cohort. After controlling for confounding variables, survival was similar in the three groups (HR 1.07, 95% CI 0.62-1.82, P = .82 for normal Tl-201 stress-only compared to normal Tc-99m rest-stress). The risk-adjusted 1-year survival was between 98.5 and 98.8% in the three groups. ConclusionsNormal stress-only Tl-201 SPECT MPI study has a similarly benign prognosis when compared to Tc-99m rest-stress and Tc-99m stress-only normal SPECT MPI studies. The stress-first design allowed for early triage of over 60% of patients and marked improvement in laboratory efficiency due to shortened test time.

Comparison of exercise-rest-reinjection Tl-201 imaging and rest sublingual isosorbide dinitrate Tc-99m MIBI imaging for the assessment of myocardial viability

Nitrate administration has been proposed to enhance the detection of myocardial viability when performing myocardial perfusion imaging. In this study, we aimed to compare Tl-201 exercise-rest-reinjection protocol with rest isosorbide dinitrate (ISDN)-Tc99m MIBI study in the same population examined for the myocardial viability. Twenty-six patients with coronary artery disease who had fixed segmental defects on exercise-rest-Tl-201 imaging were studied. All of them underwent Tl-201 reinjection study. Within 1 week of Tl-201 imaging, rest-Tc99m MIBI imaging was performed after sublingual 5 mg ISDN administration (2-day protocol). For each study, tomograms were divided into 20 segments based on three short-axis slices, one vertical long-axis representing the totality of the left ventricle and regional tracer uptake was quantitatively analyzed. Regional tracer uptake was evaluated in 20 myocardial segments for all patients. Viability was defined as presence of tracer uptake >/=50% of peak activity on each study. A total 520 myocardial segments were assessed by semi quantitative analysis. On the baseline rest Tl-201 studies, 211 segments of the 520 segments that were analyzed had <50% of peak activity. Of these segments, 42 (20%) showed reversibility after reinjection Tl-201 imaging and 55 segments (27%) described as viable on the rest ISDN-Tc99m MIBI imaging. There was 89% concordance between the ISDN-Tc99m MIBI study and Tl-201 reinjection study regarding viable myocardial segments. Of the 23 segments with discordant results, 18 were irreversible on Tl-201 reinjection study, but showed >/=50% uptake on ISDN-Tc99m MIBI. Observation of good agreement between Tl-201 reinjection and ISDN-Tc99m MIBI study studies led us to suggest the use of ISDN enhanced imaging in the evaluation of myocardial viability.

Fixed Defect on Rest/Stress Tc-99m Sestamibi Study Underestimates Myocardial Ischemia: Comparison With 24-Hour Thallium-201 Study for Short- and Intermediate-term Follow-up

We assessed whether a same day rest/stress gated Tc-99m sestamibi (MIBI) SPECT myocardial study underestimates reversible ischemia in patients with fixed perfusion defects compared with a 24-hour thallium-201 (Tl-201) study. The short- and intermediate-term outcome with or without Tl-201 reversibility was assessed. Forty-nine consecutive patients with fixed MIBI defects received an additional Tl-201 study and were evaluated. Tl-201 was given to patients with a high clinical suspicion of underestimation of reversibility. Images were interpreted semiquantitatively by 3 nuclear medicine physicians using a 17-segment, 5-point model. A summed stress score (SSS) from stress MIBI images, a summed rest score (SRS) from Tl images, and a summed difference (SDS = SSS - SRS) score were calculated. SDS >3 indicated significant Tl-201 redistribution. Composite end points included acute myocardial infarction, unstable angina needing admission, cardiac death, or revascularization within 3 and 6 months. Fifteen of 49 patients showed no Tl-201 redistribution. Thirty-four of 49 (69%) patients had significant Tl-201 redistribution, and these patients had significantly higher cardiac events (CE) at 3 months (29% vs. 7%; P = 0.039), and higher at 6 months (32% vs. 7%; P = 0.027). These patients with CE had a larger amount of Tl-201 redistribution, mean SDS 8.6 vs. 5.3 (P = 0.047). Patients with significant Tl-201 redistribution had a lower left ventricular ejection fraction (mean 37%; P = 0.001). With short- and intermediate-term follow-up, our study shows a significant association towards fixed defects on the rest/stress MIBI study underestimating CE risk when compared with a delayed Tl-201 study, especially in patients with a large amount of Tl-201 redistribution. Hence, the addition of a Tl-201 study may be useful in the management of patients with large fixed MIBI defects, especially with a depressed left ventricular ejection fraction.

A comparative evaluation of Tl-201 and Tc-99m sestamibi myocardial perfusion spect imaging in diabetic patients

Myocardial perfusion scintigraphy (MPS) is an effective tool for early diagnosis of coronary artery disease (CAD) in type II diabetes mellitus (DM). The purpose of this study was to review the comparative findings of Tc-99m MIBI and Tl-201 MPS in defining normal and abnormal myocardial segments, type and extent of the perfusion defects with reference to coronary angiography findings in diabetic patients. Thirty patients with type II DM who had abnormal Tc-99m MIBI MPS findings and underwent coronary angiography were included this study (20 male, 10 female; mean age was 64 +/- 11 years). Those patients were also investigated with Tl-201 MPS thereafter. All scintigraphic images were evaluated semiquantitatively using a 20-segments myocardial model. The perfusion of myocardial segments, reversibility and severity of defects based on defect score were compared using the MIBI and Tl-201 images in relation to coronary angiography. Diffuse slow-washout of Tl-201 was also noted. A total of 600 myocardial segments were comparatively analyzed. Diagnostic concordance between both tracers in defining normal and abnormal perfusion on a segmental basis was 88% (kappa = 0.71). The percentage of normal, reversible and non-reversible segments in the Tc-99m MIBI and Tl-201 study were 67-61%, 11-20% and 22-19% respectively. While the number of irreversible defects were similar for both tracers, more number of reversible defects were identified by Tl-201 MPS than Tc-99m MIBI (65 vs. 123, p = 0.001). No significant difference between the defect scores of both tracers was found. MPS using both tracers offered agreement in defining or excluding perfusion abnormalities in a major part of the data. However, Tl-201 MPS yielded better detection rate of myocardial ischemia than Tc-99m MIBI MPS in diabetic patients.

A normal variant on Tl-201 and Tc-99m MIBI whole-body imaging: the superior right atrial wall (auricle) and superoanterior right ventricular wall are often seen as mediastinal lesions.

The authors have often observed on Tl-201 and Tc-99m sestamibi (MIBI) scans in patients with thyroid cancer a small focus of increased uptake in the right midparasternal region (focus A) or sometimes in the lower mid chest at the level of the lower sternum (focus B) just inferomedial to focus A. The objective of this study was to assess the frequency of this finding on Tl-201 MIBI studies, to assess the incidence of true pathologic lesions corresponding to these foci, and to identify their nature. One hundred ten whole body Tl-201 studies using 4 mCi (148 MBq) and 84 MIBI studies using 20 mCi (740 MBq: first-pass, planar, and SPECT images) were reviewed. The appearance of either focus A or focus B on three orthogonal SPECT images was correlated with an atlas of cross-sectional anatomy and computed tomography. If focus A was seen on the immediate static image (obtained at the end of the first-pass acquisition without moving the patient), this image was coregistered with a selected image from the first-pass study showing the superior vena cava and also with another selected image showing the ascending aorta. Focus A was seen in 40% of Tl-201 scans and in 49% of MIBI scans, whereas focus B was seen in 20% of Tl-201 scans and 39% of MIBI scans. On correlation of the SPECT images with a cross-sectional anatomy atlas, focus A and focus B invariably corresponded to the superior portion of the right auricle and basal superoanterior right ventricular wall, respectively. These myocardial regions are prominent and sometimes appear as discrete foci because they are considerably thicker than other parts of the right atrial and right ventricular muscle, respectively, and because they are seen partly end-on in the anterior projection. The superior portion of the right auricle and basal superoanterior right ventricular myocardium often appear as isolated foci on whole-body Tl-201 and MIBl scans. Neither focus should be interpreted as a metastatic lesion in patients with possible cancer or as an ectopic parathyroid adenoma in patients with hyperparathyroid disease.

Prognostic Value of Exercise Thallium-201 Imaging Performed Within 2 Years of Coronary Artery Bypass Graft Surgery

Objectives. We sought to determine the prognostic capabilities of exercise thallium (Tl)-201 tomographic imaging performed relatively early (within 2 years) after coronary artery bypass graft surgery (CABG).Background. Exercise testing is commonly performed after CABG, but few data exist demonstrating its prognostic value in this setting.Methods. Four hundred eleven patients were followed up for a median duration of 5.8 years. Eleven prospectively chosen clinical, exercise and Tl-201 variables were tested for their associations with outcome end points by means of proportional hazards regression models.Results. During follow-up there were 60 deaths from any cause, 53 initial cardiac deaths or nonfatal myocardial infarctions (MIs) and 22 late (>3 months after the Tl-201 study) revascularization procedures. The number of abnormal Tl-201 segments on the postexercise image was the only variable in the multivariate analyses to show a significant association with all three outcome end points: chi-square 7.3, p = 0.007 for overall mortality; chi-square 8.1, p = 0.004 for cardiac death or MI; chi-square 7.8, p = 0.005 for any cardiac event. Other independent predictors of outcome were exercise duration (chi-square 10.7, p = 0.001) and age (chi-square 3.9, p = 0.049) for overall mortality and exercise angina score (chi-square 8.7, p = 0.003) for cardiac death or MI. The 5-year survival rate free of cardiac death or MI was 93% for patients without angina and a normal image or small postexercise perfusion defect versus 71% for patients with angina and a medium or large defect.Conclusions. Exercise Tl-201 imaging performed within 2 years of CABG can stratify patients into low and high risk subgroups.

Identification of Hibernating Myocardium: Comparative Accuracy of Myocardial Contrast Echocardiography, Rest-Redistribution Thallium-201 Tomography and Dobutamine Echocardiography

Objectives. We sought to evaluate the comparative accuracy of myocardial contrast echocardiography (MCE), quantitative rest-redistribution thallium-201 (Tl-201) tomography and low and high dose (up to 40 μg/kg body weight per min) dobutamine echocardiography (DE) in identifying myocardial hibernation.Background. Myocardial contrast echocardiography can assess myocardial perfusion and may therefore be useful in predicting myocardial hibernation. However, its accuracy in comparison to myocardial perfusion scintigraphy and to that of high dose DE remains to be investigated.Methods. Eighteen patients (aged [±SD] 57 ± 10 years) with stable coronary artery disease and ventricular dysfunction underwent the above three modalities before coronary revascularization. Myocardial contrast echocardiography was achieved with intracoronary Albunex. Rest echocardiographic and Tl-201 studies were repeated ≥6 weeks after revascularization.Results. Of 109 revascularized segments with severe dysfunction, 46 (42%) improved. Left ventricular ejection fraction increased from 38 ± 14% to 45 ± 13% at follow-up (p = 0.003). Rest Tl-201 uptake and the ratio of peak contrast intensity of dysfunctional to normal segments with MCE were higher (p < 0.01) in segments that recovered function compared with those that did not. Myocardial contrast echocardiography, thallium scintigraphy and any contractile reserve during DE had a similar sensitivity (89% to 91%) with a lower specificity (43% to 66%) for recovery of function. A biphasic response during DE was the most specific (83%) and the least sensitive (68%) (p < 0.01). The best concordance with MCE was Tl-201 (80%, kappa 0.57). Changes in ejection fraction after revascularization related significantly to the number of viable dysfunctional segments by all modalities (r = 0.54 to 0.65).Conclusions. In myocardial hibernation, methods evaluating rest perfusion (MCE, Tl-201) or any contractile reserve have a similar high sensitivity but a low specificity for predicting recovery of function. A limited contractile reserve (biphasic response) increases the specificity of DE. Importantly, the three techniques identified all patients who had significant improvement in global ventricular function.(J Am Coll Cardiol 1997;29:985–93)© 1997 by the American College of Cardiology

Comparison of Tc-99m MIBI and Tl-201 Uptake in Musculoskeletal Lesions

The aim of this study was to make a comparison between the uptake of Tc-99m MIBI and Tl-201 in evaluation of musculoskeletal lesions. Fourteen cases were studied. Each study consisted of a Tl-201 study followed by a Tc-99m MIBI scan. In addition, a whole-body bone scan was performed in each patient to visualize bone metastases. Tl-201 and Tc-99m MIBI uptakes were evaluated by visual assessment and by using lesion-to-background (L/B) ratio. The authors found increased Tl-201 uptake with a mean L/B ratio of 2.81 and less Tc-99m MIBI uptake with a mean L/B ratio of 2.18 in malignant lesions. Both agents showed lower uptake with mean L/B ratios of 1.6 and 1.2 in benign lesions, but there was no statistical difference between the uptakes of either Tl-201 or Tc-99m MIBI in those with malignant and those with benign lesions. In addition, false-positive imaging was observed with both Tl-201 and Tc-99m MIBI. The results demonstrated that Tl-201 and Tc-99m MIBI accumulations in musculoskeletal lesions are not specific for malignancy.

Use of Tc-99m sestamibi infusion for detection of hibernating myocardium. A preliminary report.

To evaluate whether a prolonged infusion of Tc-99m sestamibi allows for visualization of viable myocardium in areas of hypoperfused myocardium, 25 patients were prospectively studied. Each patient was imaged four times in two consecutive days in the following manner: day 1:1) immediately after injection of Tl-201 at rest, 2) 1 hour after a bolus injection of Tc-99m sestamibi at rest; and day 2: 1) imaging in the Tl-201 window for 24 hour redistribution, 2) imaging after a 1-hour infusion of Tc-99m sestamibi. The two Tc-99m sestamibi and two Tl-201 studies were evaluated for presence of redistribution. This was present both on the Tl-201 and Tc-99m sestamibi studies (concordant) in 13 cases, and absent on both the Tl-201 and Tc-99m sestamibi studies (concordant) in 9 cases. In two cases redistribution was seen on the Tl-201 images only, and in one case it was seen on the Tc-99m sestamibi images only (discordant). Tc-99m sestamibi infusion may provide information about the presence of viable myocardium which is similar to that provided by Tl-201 24-hour imaging.

Evaluation of hypoperfusion at lateral wall in hypertensive patients with TL201 and Tc99m sestamibi studies

Evaluation of hypoperfusion at lateral wall in hypertensive patients with TL201 and Tc99m sestamibi studies

Resting Tl-201 scintigraphy in the evaluation of coronary artery disease in children with Hurler syndrome.

Severe coronary artery disease may occur early in the course of mucopolysaccharidosis. The authors present radiologic, scintigraphic, and pathologic findings in five patients with Hurler syndrome. Thallium-201 myocardial scintigraphy and selective coronary angiography obtained within 2 days to 6 months were correlated in five patients. Postmortem examination of the coronary arteries was obtained in one patient within hours of angiography. Interobserver agreement on grading of scintigraphic abnormalities was poor. Nonspecific findings on Tl-201 studies included septal abnormalities in all five patients. Scintigraphic findings were corroborated by angiography and postmortem results in only 3 of 5 patients. Our findings suggest that resting Tl-201 scintigraphy has limited value in the detection of coronary artery disease in patients with Hurler syndrome.

Improved interpretation of exercise Tl-201 myocardial perfusion scintigraphy in women: characterization of breast attenuation artifacts.

Thallium-201 myocardial perfusion scintigraphy is reported to be a less accurate diagnostic test for coronary artery disease in women than in men. We retrospectively analyzed 34 Tl-201 studies obtained in 28 symptomatic women and compared them with those obtained in 32 men during the same interval. Three criteria were tested: criterion 1 was defined as abnormal scans showing any defect; criterion 2, scans showing only transient (reversible) defects; and criterion 3, scans showing either transient or "significant" (i.e., not due to breast attenuation) fixed defects. The sensitivity in women was 1.00, 0.73, and 0.93, respectively; the specificity, 0.26, 0.84, and 0.85. The best values in men were a sensitivity of 1.00 and a specificity of 0.86. The three criteria were then prospectively tested in 33 scans of 29 additional women. The sensitivity was 0.90, 0.65, and 0.80, respectively, and the specificity, 0.18, 1.00, and 0.92. Defects (usually fixed) due to breast attenuation artifact were seen frequently (30%). Criterion 3 best differentiates such defects from those resulting from coronary artery disease, making Tl-201 myocardial perfusion scintigraphy as accurate in women as in men.

Positive exercise thallium-201 test responses in patients with less than 50% maximal coronary stenosis: Angiographic and clinical predictors

The incidence and causes of abnormal thallium-201 (Tl-201) myocardial perfusion studies in the absence of significant coronary artery disease were examined. The study group consisted of 100 consecutive patients undergoing exercise Tl-201 testing and coronary angiography who were found to have maximal coronary artery diameter narrowing of less than 50%. Maximal coronary stenosis ranged from 0 to 40%. The independent and relative influences of patient clinical, exercise and angiographic data were assessed by logistic regression analysis. Significant predictors of a positive stress Tl-201 test result were: (1) percent maximal coronary stenosis (p < 0.0005), (2) propranolol use (p < 0.01), (3) interaction of propranolol use and percent maximal stenosis (p < 0.005), and (4) stress-induced chest pain (p = 0.05). No other patient variable had a significant influence. Positive Tl-201 test results were more common in patients with 21 to 40% maximal stenosis (59%) than in patients with 0 to 20% maximal stenosis (27%) (p < 0.01). Among patients with 21 to 40% stenosis, a positive test response was more common when 85 % of maximal predicted heart rate was achieved (75%) than when it was not (40%) (p < 0.05). Of 16 nonapical perfusion defects seen in patients with 21 to 40% maximal stenosis, 14 were in the territory that corresponded with such a coronary stenosis. Patients taking propranolol were more likely to have a positive Tl-201 test result (45%) than patients not taking propranolol (22%) (p < 0.05). Although patients with stress-induced chest pain more often had a positive Tl-201 test result than those without chest pain, this difference did not reach statistical significance. However, Tl-201 perfusion defects were more frequently seen when typical angina pectoris was elicited than when atypical chest pain developed (p < 0.05). The high frequency of Tl-201 defects associated with 21 to 40% stenoses and the close correlation of such defects with myocardial territory supplied by these stenoses suggests that such coronary lesions may have true hemodynamic impact, especially at high levels of stress. In addition, the high incidence of positive Tl-201 studies in patients taking propranolol suggests that an attempt be made to wean patients off β-blocker treatment before Tl-201 exercise testing.

Abnormal thallium-201 scans in patients with chest pain and angiographically normal coronary arteries

We reviewed the exercise thallium-201 (Tl-201) scans arid clinical data of 41 patients with chest pain and normal coronary arteries to identify clinical factors associated with “false-positive” studies. Exercise Tl-201 studies were performed before angiography and often precipitated referral. Sex, beta-blocker therapy, anginal pattern, and results of exercise electrocardiography were evaluated and compared with Tl-201 imaging. A negative Tl-201 study was the most common finding (p < 0.005). Of the 41 patients, 11 (27%) had abnormal exercise Tl-201 scans. No clinical factor was significantly associated with a false-positive Tl-201 scans. Of the 11 patients with abnormal scans, 9 had ≥1 cardiac abnormality: right bundle branch block in 2, mitral Valve prolapse in 3, paroxysmal atrial fibrillation in 2, abnormal left ventricular diastolic pressure in 3, and left bundle branch block in 1. Thus, (1) when results of exercise Tl-201 imaging are used to refer patients for angiography, “false-positive” Tl-201 studies are common; (2) sex, beta blockade, anginal pattern, and results of exercise electrocardiogram are not useful predictors of a false-positive Tl-201 study; and (3) patients with chest pain, normal coronary arteries, and abnormal Tl-201 scans frequently have other cardiac abnormalities.