Tl-201 SPECT Images Research Articles

Reduction of contribution of scattered photons by optimization of energy window settings in 201Tl SPECT imaging: a simulation study

Introduction and Objectives: detection of Compton scattered photons is one of the effective factors in reducing the quality of SPECT images. The aim of this study is to reduce the contribution of scattered counts included in the main energy window for 201Tl SPECT imaging in two steps: first step, by determining the location and width of the optimal main energy window, and second step, by using the optimal correction methods.Materials and Methods: in this study, the Monte Carlo program is used to simulate the required phantoms (a cylindrical phantom consist of two small cylinders with different diameters and a simple cardiac phantom), and to produce the projections related to different energy windows.Results: according to the simulation results, among the 13 investigated energy windows, the 30%-wide window with the central energy of 75 keV is determined as the optimal main window for 201Tl SPECT imaging. Also, from the results of this study, two energy window settings are proposed as the most suitable settings for scatter correction of 201Tl SPECT images. In the first case, a second energy window (a 34%-wide window centered at 51 keV) with counts approximately equal to the scattered counts of the optimal main window, and in the second case, two narrow windows (a 8%-wide window centered at 56 keV and a 6%-wide window centered at 92 keV) on both sides of the optimal main window and at a certain distance from two sides of this window are determined as the most suitable energy window settings for these methods.Conclusion: using the optimal main window together with the optimal scatter correction settings proposed in this study leads to a significant improvement of the contrast of 201Tl SPECT images with an acceptable noise level.

Evaluation of Tl-201 SPECT imaging findings in prostate cancer

To compare with histopathological findings the findings of prostate cancer imaging by SPECT method using Tl-201 as a tumor seeking agent. The study comprised 59 patients (age range 51-79 years, mean age 65.3 ± 6.8 years) who were planned to have transrectal ultrasonography (TRUS)-guided biopsies due to suspicion of prostate cancer between April 2011 and September 2011. Early planar, late planar and SPECT images were obtained for all patients. Scintigraphic evaluation was made in relation to uptake presence and patterns in the visual assessment and to Tumor/Background (T/Bg) ratios for both planar and SPECT images in the quantitative assessment. Histopathological findings were compatible with benign etiology in 36 (61%) patients and malign etiology in 23 (39%) patients. Additionally, comparisons were made to evaluate the relationships between uptake patterns,total PSA values and Gleason scores. A statistically significant difference was found between the benign and malignant groups in terms of uptake in planar and SPECT images and T/Bg ratios and PSA values. No statistically significant difference was found between uptake patterns of planar and SPECT images and Gleason scores in the malignant group. SPECT images were superior to planar images in the comparative assessment. Tl-201 SPECT imaging can provide an additional contribution to clinical practice in the diagnosis of prostate cancer and it can be used in selected patients.

Abstract 19973: Dynamic Thallium-201 SPECT/CT Provides Quantitative Index of Myocardial Flow and Viability: Validation in Porcine Post-Myocardial Infarction Model

Introduction: Thallium-201 (Tl-201) SPECT imaging is routinely used to evaluate relative myocardial perfusion and/or viability. In this study, we have evaluated Tl-201 kinetics in a porcine model of myocardial infarction (MI) with dynamic imaging on a hybrid SPECT/CT system. Methods: Tl-201 SPECT and contrast CT imaging were performed on hybrid SPECT/64-slice CT (GE Discovery NM/CT 570c) in Yorkshire pigs (n=5) one week following a 90 min balloon occlusion of the LAD below the first diagonal branch. Tl-201 (83-158 MBq) was injected after the initiation of a 900s list-mode acquisition. The list-mode data was reconstructed with MLEM using 30 iterations creating 23 frames (12 x 10s; 6 x 30s; 5 x 120s). Reconstructed dynamic SPECT data was analyzed using FlowquantTM semi-automated analysis software with a 1-compartment model. K1 (index of flow) and k2 (index of viability) were assessed within a 17-segment model of the left ventricle. Four segments within the central infarcted LAD territory were compared to six segments of the contralateral inferolateral wall. The same segments were analyzed for wall thickening from ECG-gated contrast CT scans using centerline approach (GE AW Cardiac Function Xpress). Results: K1 was significantly decreased in the MI vs contralateral normal regions (0.52 ± 0.17 vs 0.61 ± 0.16 ml/min/g, p<0.02). K2 an index of tissue viability was significantly increased in the MI region (0.42 ± 0.19 vs 0.32 ± 0.12 /min, p<0.04), reflecting accelerated Tl-201 washout in MI. Wall thickening in the same MI region was significantly decreased (0.33 ± 1.5 mm vs 3.3 ± 1.9 mm, p<0.005). Conclusions: Dynamic Tl-201 SPECT/CT imaging provides a quantitative index of both myocardial flow and viability using a 1-compartment model. This preliminary pre-clinical demonstrates the potential for dynamic Tl-201 SPECT imaging to quantify myocardial viability early post-MI.

Comparison of an adaptive neuro-fuzzy inference system and an artificial neural network in the cross-talk correction of simultaneous 99m Tc / 201Tl SPECT imaging using a GATE Monte-Carlo simulation

The aim of this study is to compare the adaptive neuro-fuzzy inference system (ANFIS) and the artificial neural network (ANN) to estimate the cross-talk contamination of 99mTc / 201Tl image acquisition in the 201Tl energy window (77 ± 15% keV). GATE (Geant4 Application in Emission and Tomography) is employed due to its ability to simulate multiple radioactive sources concurrently. Two kinds of phantoms, including two digital and one physical phantom, are used. In the real and the simulation studies, data acquisition is carried out using eight energy windows. The ANN and the ANFIS are prepared in MATLAB, and the GATE results are used as a training data set. Three indications are evaluated and compared. The ANFIS method yields better outcomes for two indications (Spearman’s rank correlation coefficient and contrast) and the two phantom results in each category. The maximum image biasing, which is the third indication, is found to be 6% more than that for the ANN.

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.

FDG-PET versus Thallium-201 SPECT in the evaluation of putative CNS lymphoma in AIDS patients

1537 Background: The evaluation of CNS lesions in AIDS patients is challenging as both CNS lymphoma and non-neoplastic lesions can have similar clinical presentations and imaging findings. Both Tl-201 SPECT and FDG PET imaging have been used to differentiate malignancy from infection. This study investigates the accuracy of FDG PET compared to Tl-201 SPECT in the diagnosis of CNS lymphoma in patients with AIDS-associated CNS lesions. Methods: Nine patients with AIDS who were found to have rim enhancing brain lesions on MRI underwent both Tl-201 SPECT and FDG PET imaging prior to diagnosis. Diagnosis was made by stereotactic brain biopsy in 6 pts and clinical follow-up in the remaining 3. FDG PET of the brain was performed using a dedicated PET/CT instrument (GE Discovery) 1 hour after 444 MBq FDG. Brain SPECT was performed on a dual head gamma camera (GE Hawkeye) with 185 MBq Tl-201. Images were reviewed along with MRI for anatomic correlation by 2 experienced nuclear medicine physicians blinded to the diagnosis. Results: 43 MRI lesions in 9 patients were evaluated. Clinically, 5 pts (18 lesions) were diagnosed with lymphoma (4 biopsy proven, 1 with known history of lymphoma), and 4 pts (25 lesions) were diagnosed with toxoplasmosis (2 with negative biopsies for malignancy, 2 with clinical course consistent with toxoplasmosis). FDG PET had true positive results for lymphoma in 5 of 5 pts, while Tl-201 SPECT was true positive in only 2 of 5. FDG PET had true negative results in 4 of 4 pts with toxoplasmosis, while Tl-201 had false positive results in 2 of 4. FDG PET had positive and negative predictive values of 100%, while Tl-201 SPECT had PPV 50% and NPV 40%. On a lesion basis, PET showed increased uptake of FDG in 8 of 18 brain lesions in patients with lymphoma, while SPECT showed increased uptake of Tl-201 in 4 of 18 lesions. Tl-201 was positive in 2 lesions in patients diagnosed with toxoplasmosis, while FDG had no false positive lesions. Conclusion: In this limited study, FDG PET proved to be superior to Tl-201 SPECT in the differentiation of CNS lymphoma from toxoplasmosis (overall accuracy 100% vs 44%, respectively). With the increasing availability of FDG PET, this test should probably supplant Tl-201 SPECT as the study of choice following conventional imaging (CT, MRI) of CNS lesions in AIDS patients. No significant financial relationships to disclose.

Evaluating the Prevalence of Silent Coronary Artery Disease in Asymptomatic Patients With Spinal Cord Injury

To evaluate the prevalence of coronary artery disease (CAD) in patients with spinal cord injury (SCI), 47 clinically asymptomatic SCI patients received thallium-201 myocardial perfusion single photon emission computed tomography (Tl-201 SPECT) after dipyridamole administration for the diagnosis of CAD. There were 4 groups as follows; group 1: 13 patients with quadriplegia and complete SCI, group 2: 11 patients with quadriplegia and incomplete SCI, group 3: 11 patients with paraplegia and complete SCI, and group 4: 12 patients with paraplegia and incomplete SCI. There were no significant differences in sex distribution, ages, SCI duration, or CAD risk factors among the SCI patients in the 4 groups. All Tl-201 SPECT images were interpreted by the agreement of 2 experienced nuclear medicine physicians without prior knowledge of the patients' histories. A total of 30 of 47 (63.8%) SCI patients had abnormal Tl-201 SPECT findings. Among the 4 groups of SCI patients, those in groups 1 and 4 had the significantly highest and lowest prevalences of abnormal Tl-201 SPECT findings, respectively. We concluded that combined quadriplegia and complete SCI is an important CAD risk factor in SCI patients based on the objective evidence of intravenous dipyridamole cardiac stress testing with Tl-201 SPECT.

Exercise electrocardiography is a poor predictor of thallium-201 SPECT-defined myocardial ischemia following coronary artery bypass graft surgery

Background: While the exercise-ECG is commonly used to assess patients following coronary artery bypass grafting (CABG), the predictive value of exercise-induced ST-segment shifts (STΔ) for the detection of myocardial ischemia in this population has not been fully validated. We used the surrogate marker of reversible myocardial perfusion defects on 201Tl SPECT imaging, and compared this to exercise induced STΔ. We hypothesized that post-CABG (PCABG) the diagnostic utility of STΔ may differ from that in the general population. Methods: 850 PCABG subjects (761 M, 89 F) with unequivocally ECG negative (N=410) or positive (N=440) treadmill exercise studies (GXT) had their GXT and simultaneous exercise-redistribution 201Tl SPECT compared to a control group of 882 subjects with known or suspected CAD. Patients were matched for their clinical and SPECT characteristics. Exercise induced ischemia was defined as reversibility on 201Tl SPECT imaging. Results: Correlation and agreement between STΔ and reversibility was worse PCABG than in the control group (Pearson's R =0.264 vs 0.344 p < 0.001; kappa = 0.253 vs 0.341 p < 0.001). This trend persisted even when patients with resting ST-T wave abnormalities or Q-waves were excluded (Pearson's R = 0.305 vs 0.363 p < 0.001; kappa = 0.298 vs 0.361 p < 0.001). The specificity of ST? to predict ischemia as defined by reversibility was almost identical PCABG and in the control group (67% vs 68%), but sensitivity was significantly reduced in the PCABG (61% vs 67%). In males, there were no significant differences between the positive predictive value (PPV) in the PCABG and in the control group (78% in both). The negative predictive value was much lower PCABG (46% vs 59%). In women, the PPV was higher PCABG (72% vs 65%), whereas the NPV was much lower (45% vs 69%). Conclusion: Following CABG, correlation and agreement between significant exercise-induced ST-segment shift and myocardial ischemia as defined by 201Tl-SPECT are worse than in the general population. In both genders, after CABG there is an increase of false negative exercise-ECG tests.

The usefulness of dipyridamole thallium-201 single photon emission computed tomography for predicting perioperative cardiac events in patients undergoing non-cardiac vascular surgery.

The aim of this study was to evaluate the usefulness of dipyridamole Tl-201 myocardium single photon emission computed tomography (201Tl-SPECT) for predicting perioperative cardiac events in patients with arteriosclerosis obliterans (ASO) and abdominal aortic aneurysm (AAA) undergoing non-cardiac vascular surgery. Preoperative dipyridamole 201Tl-SPECT imaging in association with clinical risk assessment was performed in 224 consecutive patients (97 ASO and 127 AAA). The patients were classified into three groups, including low-risk (n = 173, 77%), intermediate-risk (n = 39, 18%), and high-risk (n = 12, 5%) groups according to the clinical risk stratification. The prevalence of reversible Tl-201 defect was significantly higher in the high-risk group than that in the low-risk group (83% vs. 14%, p < 0.001). In 180 patients who underwent vascular surgery, 9 patients (5.0%) had perioperative cardiac events, including heart failure (n = 1), unstable angina (n = 2), and other cardiac events such as arrhythmias (n = 6). The clinical variables including the clinical risk stratification did not significantly correlate with the perioperative cardiac events. In contrast, the reversible defect on 201Tl-SPECT was the only variable to predict perioperative cardiac events by a stepwise logistic regression analysis (odds ratio 7.0, 95% confidence interval 1.7-28.0, p = 0.007). It was also a significant predictor of perioperative cardiac events in a subgroup of low risk patients (odds ratio 11.6, 95% confidence interval 2.3-57.4, p = 0.004). The sensitivity and specificity of the reversible defect for predicting perioperative cardiac events were 55.6% and 84.8% in all operated patients, and 57.1% and 89.7% in low risk patients, respectively. The preoperative dipyridamole 201Tl-SPECT was useful for predicting perioperative cardiac events in patients with vascular diseases, even in patients identified as having a low risk based on the clinical risk assessment.

Use of 201Tl SPECT imaging to assess the response to therapy in patients with high grade gliomas.

To assess the potential role of 201Tl single photon emission tomography (201-Thallium SPECT) when compared to other imaging modalities in the evaluation of the response to therapy in high grade gliomas. Twenty patients with histologically proved high grade glioma have been included: 15 with glioblastoma (GBM), 3 with anaplastic astrocytoma (AA) and 2 with anaplastic oligoastrocytoma (AOA). Patients were assessed by 201Tl SPECT, computed tomography (CT) and magnetic resonance imaging (MRI) at (a) either at the moment of maximum response to first line chemotherapy, or after the completion of radiotherapy and chemotherapy if post-surgical residual disease was present, and (b) after the completion of second line chemotherapy if disease persisted, or either a relapse or disease progression was confirmed. Final response was evaluated according to the McDonald criteria, and by comparing SPECT, CT and MRI results. According to the McDonald criteria, clinical response after first line chemotherapy was 5 partial response, 7 stable disease and 8 progressive disease. Evaluation by 201Tl SPECT was in agreement with such criteria in nearly all patients (90%). MRI findings closely agreed with the clinical follow-up. CT findings clearly differed from those observed by SPECT and MRI. After second line therapy, 10 patients progressed, 3 had stable disease and 7 had partial response. 201Tl SPECT agreed with the clinical status in 89% cases, whereas MRI and, specially CT, fared significantly lower. Compared to conventional neuroimaging, 201Tl SPECT added valuable information in the assessment of the response to therapy in our patient population; whenever findings were not conclusive and in the case of disagreement between CT and MRI findings.

Long-term prognostic value of stress-redistribution-reinjection Tl-201 imaging in patients with severe left ventricular dysfunction and coronary artery bypass surgery.

This study sought to evaluate the long-term prognostic significance of stress-redistribution-reinjection Tl-201 imaging in patients with severe left ventricular (LV) dysfunction and coronary artery bypass surgery. Preoperative stress-redistribution-reinjection Tl-201 imaging detects viable but asynergic segments which show functional improvement postoperatively and is considered as a valuable noninvasive method in selection of patients with severe LV dysfunction for revascularization. The long-term prognostic value of the reinjection technique remains unclear. Fifty-two patients with severe LV dysfunction (mean ejection fraction (EF) 0.32+/-0.03) who underwent coronary artery bypass surgery in 1993-1994 were included in the study. Patients had follow-up 49+/-12 months. LV function was assessed by two-dimensional echocardiography. Perfusion was assessed by Tl-201 SPECT imaging and was graded on a four-point scale (0 = normal, 3 = absent uptake) using the 20 segment model. Perfusion index was derived by adding the score of all segments and dividing these by 20. Patients were divided into two groups. Group A comprised patients with seven and more dysfunctional viable myocardial segments. Group B included patients with less than seven dysfunctional but viable segments. Mean EF increased from 0.32+/-0.03 to 0.46+/-0.04. Mean perfusion index did not show a significant difference as a whole during follow-up compared to the early postoperative values (0.9+/-0.4 and 1.1+/-0.4, p = NS). When adequacy of revascularization was considered, the predictive value of a positive preoperative viability test for functional improvement was 82%. Nineteen cardiac events occurred in group B patients and six in group A patients: six deaths (four from cardiac and two from noncardiac causes), 13 myocardial infarctions (MI). Multivariate Cox survival analysis identified the number of viable segments detected preoperatively (chi2 = 7.2, p = 0.002), postoperative improvement in Tl-uptake (chi2 = 6.6, p = 0.01) and functional improvement (chi2 = 5.3, p = 0.03) postoperatively as independent predictors of cardiac events. Preoperative EF and functional capacity were not associated with cardiac events in long-term prognosis. These data suggest that preoperative stress-redistribution-reinjection Tl-201 imaging, specifically the number of viable segments detected preoperatively and postoperative improvement in Tl-201 uptake provide important long-term prognostic information in patients with severe LV dysfunction who had coronary artery bypass surgery.

Usefulness of BMIPP SPECT to evaluate myocardial viability, contractile reserve and coronary stenotic progression after reperfusion in acute myocardial infarction.

Using combined 123I-BMIPP (BMIPP), 201Tl (Tl) and 99mTc-PYP (PYP) myocardial SPECT imaging, risk areas of acute myocardial infarction were documented in the acute stage, and then these images were evaluated for how well they reflected muscle viability, contractile reserve and coronary stenotic progression subsequent to reperfusion therapy. Patients who only experienced a first attack of myocardial infarction were enrolled. In total, 36 cases who had had the occluded artery successfully reperfused were examined during the past year. They had no significant vessel disease except for the culprit single artery. The patients were comprised of 32 men and 4 women. The mean age was 59.5 years. All patients underwent coronary angiography and left ventricular (LV) angiography in the emergency room. BMIPP/Tl and PYP myocardial SPECT were conducted in the acute stage and chronic stage. In the chronic stage LV angiography was repeated to assess the improvement of LV wall motion. The response to postextrasystolic potentiation (PESP) testing was performed to estimate myocardial contractile reserve. The risk area of acute myocardial infarction (AMI) was documented by reduced BMIPP accumulation. The size of reduced BMIPP accumulation was larger than that of PYP accumulation. A BMIPP/Tl discrepancy and PYP accumulation were documented to assess myocardial viability. Both improvement in LV wall motion and augmentation of PESP response were more closely related to a BMIPP/Tl discrepancy in the presence or absence of PYP accumulation. Therefore, it would be possible to evaluate myocardial viability and contractile reserve by the BMIPP/Tl discrepancy. In patients with good viability, it is important to predict whether there is coronary stenotic progression or not. In this study, we demonstrated that most patients with improved BMIPP images had no significant progression at the site of intervention. Serial observation of BMIPP images from the acute stage to the chronic stage might enable us to predict the progression of coronary stenosis.

Comparación entre la eco-dobutamina y talio-201 SPECT reposo-redistribución en la valoración de la viabilidad miocárdica considerando el PET como patrón oro

To compare Tl-201 SPECT and dobutamine stress echocardiography for the detection of myocardial viability in patients with severe left ventricular dysfunction using metabolic imaging by positron emission tomography as the standard reference. We studied 25 consecutive patients with severe coronary artery disease and left ventricular dysfunction that underwent two different diagnostic modalities for evaluating myocardial viability: stress echocardiography with incremental doses of dobutamine from 5 up to 40 g/kg/min in 3 min stages, and 201 Tl SPECT using a rest-redistribution protocol with delayed images obtained at 4 hours. Fluorodeoxyglucose uptake by PET was used as the gold standard. Viability criteria were as follows, for 201Tl SPECT imaging: normal uptake at rest and presence of redistribution in the delayed images, for dobutamine stress echocardiography: sustained improvement and biphasic response. Sensitivity of thallium redistribution was 46%, for normal uptake, plus redistribution 82%, 34% for dobutamine biphasic response and 58% for sustained improvement plus biphasic response. Specificity of biphasic response was 82% and that of redistribution 67%. Stepwise logistic regression indicated that biphasic wall motion response during dobutamine stress echocardiography (2.01 CI 95%; 1.10 to 3.99) and the presence of redistribution plus normal uptake at rest with thallium imaging (2.68 CI 95%; 1.42 to 5.13) were the best predictors of viability. These results were the same when both techniques were analyzed together. Biphasic wall motion response during dobutamine stress echocardiography and the normal uptake plus presence of redistribution with thallium imaging were the best pre

Contributions of nuclear cardiology to diagnosis and prognosis of patients with coronary artery disease.

In the past decade, significant advances have been made in the ability to image the heart with radionuclide tracers under stress and resting conditions in patients with suspected or known coronary artery disease (CAD) for the detection of ischemia, determination of prognosis, assessment of myocardial viability, preoperative risk assessment for patients undergoing noncardiac surgery, and evaluation of the efficacy of revascularization in patients undergoing coronary artery bypass surgery or an interventional procedure.1 For many years, planar imaging and SPECT with 201Tl constituted the only scintigraphic techniques available for detecting CAD and assessing prognosis in patients undergoing stress perfusion imaging. The major limitation of 201Tl scintigraphy is the high false-positive rate observed in many laboratories, which is attributed predominantly to image attenuation artifacts and variants of normal that are interpreted as defects consequent to a significant coronary artery stenosis. Although quantification of 201Tl images improves specificity, the false-positive rate remains problematic, particularly in women and in obese patients. Breast attenuation artifacts in women are sometimes difficult to distinguish from perfusion abnormalities secondary to inducible ischemia or myocardial scar. In recent years, new 99mTc-labeled perfusion agents have been introduced into clinical practice to enhance the specificity of SPECT and to provide additional information regarding regional and global left ventricular systolic function via ECG gating of images. It was immediately apparent that the quality of images obtained with these new 99mTc-labeled radionuclides was superior to that of images obtained with 201Tl because of the more favorable physical characteristics of 99mTc imaging with a gamma camera. With 99mTc, doses of ≈10 to 20 times higher than those that are feasible with 201Tl can be administered, yielding images with higher count density. 99mTc demonstrates less scatter and attenuation than 201Tl, which is associated …

Evaluation of myocardial infarct size in rat heart by pinhole SPECT

Background. High-resolution single photon emission computed tomography (SPECT) with a pinhole collimator is a new method for evaluating the regional properties of radiopharmaceuticals in small laboratory animals in vivo. Although several reports of normal images of rat taken by this new technique are available, there are as yet few reports on its use in disease models, such as myocardial infarction. In this study, we clearly visualized myocardial flow in the rat heart with myocardial infarction using this system, and evaluated the relationship between SPECT images and histologic analysis. Methods and Results. For visualization of myocardial flow in rat heart, 201Tl images were taken just before and 24 days after left coronary artery ligation. The images were taken using a 4-head SPECT scanner with pinhole collimators. The percent infarct size on 201Tl-SPECT imaging (%SI) and the defect score were then assessed and compared with the percent infarct size on histologic analysis (%HI). Both the %SI and defect score correlated well with %HI ( r= 0.97 and 0.74, respectively). Conclusion. Serial SPECT imaging using pinhole collimators permits estimates of myocardial flow even in small laboratory animals noninvasively in vivo.

Thallium-201-chloride and technetium-99m-MIBI SPECT of primary and metastatic lung carcinoma.

We compared technetium-99m-MIBI (Tc-99m MIBI) with thallium-201-chloride (Tl-201) SPECT imaging in patients with lung carcinoma. In addition, we compared the imaging characteristics of Tl-201 and Tc-99m MIBI after radiation therapy. Thirty-seven patients with primary lung carcinoma were evaluated with SPECT imaging for metastasis to the mediastinal lymph nodes and brain. Patients were imaged with Tl-201 chloride images 10 and 180 min after injection. Patients were also imaged 10 min after injection of Tc-99m MIBI. The sensitivity of Tl-201 SPECT for the primary lesion and brain metastasis was 97.1% and 70.0% respectively at 10 min and 97.1% and 60.0% at 180 min. The sensitivity of Tc-99m MIBI SPECT was 97.1% (for the identification of the primary lesion) and 50.0% (for the detection of brain metastasis) at 10 min. The uptake ratios (count in tumor/count in normal lung or brain) at 10 min on the Tl-201 SPECT and on the Tc-99m MIBI SPECT were not significantly different for the primary tumor or for brain metastasis. The uptake ratios were better for Tc-99m MIBI than for Tl-201 [2.82 vs. 1.99 (p<0.05)] for mediastinal lymph nodes. Decreasing uptake ratios and retention index with both agents after radiation therapy are concordant to the follow-up clinical course. Tc-99m MIBI SPECT is more sensitive in the detection of metastasis to mediastinal lymph nodes than Tl-201 SPECT.

Dipyridamole Tl-201 SPECT in Hypertrophic Cardiomyopathy with Asymmetric Septal Hypertrophy:Characteristics of Perfusion Abnormality and Correlation with Clinical Parameters

Background and Objectives:Exercise myocardial perfusion scans in patients with hypertrophic cardiomyo- pathy have shown reversible perfusion abnormalities with unknown clinical significance. We performed this study to characterize dipyridamole Tl-201 SPECT imaging and correlate with clinical findings in patients with hypertrophic cardiomyopathy. Methods:Tl-201 SPECT was performed in 25 patients of hypertrophic cardiomyopathy with asymmetric septal hypertrophy and 20 normal controls after dipyridamole infusion (0.56 mg/kg. Myocardial wall was divided into 8 segments. Tl-201 uptake and relative washout rate were calculated. Results:Tl-201 SPECT showed significantly lower Tl-201 uptake in basal septal (81.3±3.4% vs 78.2±6.4%, p<0.05 and apical septal wall on stress (88.2±4.7% vs 83.9±6.5%, p<0.05 and higher apical septal (86.6±5.2% vs 89.2±3.1%, p<0.05 and apical anterior wall uptake (88.7%±4.0% vs 91.4±4.9%, p<0.05 on redistribution images in patients with hypertrophic cardiomyopathy. Basal lateral wall uptake of hypertrophic cardiomyopathy was significantly lower than normal control on both stress (84.7±3.5% vs 81.2 ±7.3%, p<0.05 and redistribution images (85.0±5.8% vs 76.8±7.2%, p<0.0001. The septum/lateral uptake ratio of patients on rest image was significantly higher than that of normal controls (0.98±0.07 vs 1.07±0.10, p<0.001. There was no difference in age, sex, symptom, cardiac medication and the parameters of 2D-echo including left ventricular outflow obstruction between subgroups of normal vs abnormal washout in patients with hypertrophic cardiomyopathy. Conclusion:Dipyridamole Tl-201 myocardial SPECT shows reduced

Abnormal thallium-201 chloride myocardial SPECT findings with noncritical coronary angiography in a patient after coronary artery bypass graft

We report on a patient with a previous CABG and symptoms similar to syndrome X who had normal angiography and significant abnormal 201Tl perfusion. The discrepancy of the two imaging modalities could have occurred because, fundamentally, SPECT is a physiologic measurement that reflects perfusion of the myocardium, while coronary angiography reflects only anatomy, and it is known that anatomy may not predict perfusion well. Coronary angiography may underestimate the severity of coronary disease, atheromatosis involving coronary vascular wall, and its related perfusion. Another possibility is that coronary blood supply was diverted/stolen by 1 proximal branch of the left internal mammary artery during the exercise. Lastly, during stress there was an inability to increase flow reserve, resulting in decreased perfusion pressure to the collateral supply of the septal perforators from the saphenous venous graft to the distal right coronary artery. Stress and delayed 201Tl SPECT imaging provide insight into regional flow, cellular integrity, and viability, providing a valuable technique of assessing the presence of resting and provokable ischemia.

MR and TL-201 Spect Imaging with Pathologic Correlation for the Assessment of CNS Lymphoma vs. Toxoplasmosis in AIDS Patients

Analyze the value of TL-201 (Tl) brain single-photon emission computed tomography (SPECT), to differentiate CNS lymphoma from toxoplasmosis in AIDS patients. Twenty-four AIDS patients with MR enhancing lesion(s), underwent a brain Tl SPECT. Final diagnosis was established by pathology and clinical/MR follow-up. Nine patients had CNS tumor, 9 toxoplasmosis and 6 other non-tumorous lesions. The sensitivity of T1 to diagnose CNS tumor was 77% and the specificity 93%. Two false negative studies correspond to tumors with significant necrosis. T1 proved useful for differentiating brain neoplasm from toxoplasmosis. Tumors with significant necrosis, did not show the expected increase in T1 uptake. Determination of T1 uptake ratios help detect tumor with faint tracer uptake.

What is the prevalence and prognostic significance of ischemia detected by Tl-201 SPECT imaging proximal to bypass graft insertion in patients who have undergone coronary artery bypass grafting (CABG)?

What is the prevalence and prognostic significance of ischemia detected by Tl-201 SPECT imaging proximal to bypass graft insertion in patients who have undergone coronary artery bypass grafting (CABG)?