Dual-isotope Single-photon Emission Tomography Research Articles

Myocardial viability estimation during the recovery phase of stress echocardiography after acute beta‐blocker administration

Myocardial viability assessment in severely dysfunctional segments by dobutamine stress echocardiography (DSE) is less sensitive than nuclear scanning. To assess the additional value of using the recovery phase of DSE after acute beta-blocker administration for identifying viable myocardium. The study included 49 consecutive patients with ejection fraction (LVEF)<or=35%. All patients underwent DSE evaluation at low-high dose and during recovery phase, and dual-isotope single photon emission tomography (DISA-SPECT) evaluation for viability of severely dysfunctional segments. Patients with >or=4 viable segments were considered viable. Coronary revascularization followed within 3 months in all patients. Radionuclide evaluation of LVEF was performed before and 12 months after revascularization. Viability with DISA-SPECT was detected in 463 (59%) segments, while 154 (19.7%) segments presented as scar. The number of viable segments increased from 415 (53%) at DSE to 463 (59%) at DSE and recovery, and the number of viable patients increased from 43 to 49 respectively. LVEF improved by >or=5% in 27 patients. Multivariate regression analysis showed that, DSE with recovery phase was the only independent predictor of >or=5% LVEF improvement after revascularization (OR 14.6, CI 1.4-133.7). In this study, we demonstrate that the recovery phase of DSE has an increased sensitivity for viability estimation compared to low-high dose DSE.

Contractile Reserve, Thallium-201 Reverse Redistribution and Mismatch Between Perfusion and Metabolism in Reperfused Infarct-related Myocardium With Delayed and Incomplete Functional Recovery

We investigated simultaneously the correlations between dobutamine-induced contractile reserve (CC), thallium-201 reverse redistribution (RR) and a mismatch between perfusion and metabolism (MM) to the magnitude of functional recovery. In 32 patients with coronary angioplasty early after infarction, echocardiography was performed at low-dose dobutamine stress within 1 week and at resting state at 1 month. Thallium-201/iodine-123 beta-methyl-iodophenyl pentadecanoic acid (BMIPP) dual-isotope single photon emission tomography was performed at 1 month. Wall motion and the uptake of each tracer were scored as 0 to 2 in the infarct-related segments, and CC, RR, and MM were evaluated in the infarct-related segments. In 71 akinetic or dyskinetic segments before reperfusion, the initial thallium-201 uptake and initial BMIPP uptake scores and the 4 hour redistribution thallium-201 uptake scores were less severe in the group with complete functional recovery (group A), followed by the group with incomplete recovery (group B) and then the group with no recovery (group C) (each P < 0.0001). CC was the greatest in group A, followed by group B, and then group C (76.2% in 16/21, 60% in 15/25, 36% in 9/25, P = 0.0212). RR and MM were greater in group B (52% in 13 and 64% in 16) than in groups A and C (19% in 4 and 8% in 2, 33.3% in 7 and 24% in 6, P = 0.0013 and P = 0.0113). The intensity of functional damage reflects perfusion and metabolism, but the delayed and incomplete functional recovery after reperfusion may be closely related to RR, MM, and CC.

Severity of exercise-induced ischemia with chest pain and recovery from ischemia after the disappearance of chest pain.

The severity of exercise-induced painful ischemia and its recovery after the disappearance of pain are unknown. The aim of this study was to investigate the difference in severity of ischemia at both exercise and postexercise between painful ischemia and painless ischemia. After injections of technetium-99m tetrofosmin at peak ergometer exercise and thallium-201 at 3 minutes postexercise, dual-isotope single photon emission tomography was performed in 78 patients with angiographically proven ischemic heart disease. The extent of ischemic areas (the number of areas), the depth of ischemia in the ischemic area (the severity score of ischemia) and the extension of ischemia toward long axis of the left ventricle (the number of left ventricular levels with ischemic areas in apical, middle, and basal levels) at both exercise and postexercise were compared on the basis of the presence of pain and a history of diabetes mellitus (DM). The symptoms improved within 3 minutes postexercise in all painful ischemia patients. Of 59 patients with reversible ischemia, except for 4 painful ischemia patients with DM, the extent and depth of ischemia at postexercise were more severe in 14 painful ischemia patients without DM and 13 painless ischemia patients with DM than 28 painless ischemia patients without DM (extent; 2.9 +/- 1.7 areas, 3.5 +/- 2.8 areas versus 1.4 +/- 1.8 areas, P = 0.005, depth; 3.8 +/- 3.1 scores, 5.8 +/- 5.4 scores versus 1.9 +/- 3.0 scores, P = 0.0084, respectively) despite a comparable severity of ischemia at peak exercise (extent; 5.4 +/- 2.6 areas, 6.0 +/- 2.4 areas versus 4.3 +/- 3.3 areas, depth; 9.3 +/- 5.7 scores, 10.7 +/- 7.3 scores and 7.5 +/- 8.1 scores, all NS). The extension of ischemia toward long-axis of the left ventricle at both peak exercise and postexercise was more severe in the former 2 groups than the latter group (peak exercise; 2.4 +/- 0.6 levels, 2.5 +/- 0.7 levels versus 1.9 +/- 0.8 levels, P = 0.0263, postexercise: 1.8 +/- 0.7 levels, 1.5 +/- 0.9 levels versus 0.8 +/- 0.8 levels, P = 0.0014, respectively). The presence of chest pain is related to the extension of ischemia toward long-axis of the left ventricle, and the disappearance of pain was not related to the recovery of ischemia.

Significance of ST-segment morphology noted on electrocardiography during the recovery phase after exercise in patients with ischemic heart disease as analyzed with simultaneous dual-isotope single photon emission tomography

Background The significance of differences in electrocardiographic morphology that occur during the recovery phase after exercise has not been clarified. We investigated the relationship between postexercise electrocardiographic morphology and the pattern of residual ischemia measured at that time. Methods Exercise dual-isotope single photon emission computed tomography was performed on 171 consecutive patients with chest pain syndrome. After injection of technetium-99m tetrofosmin at peak exercise and thallium-201 at 3 minutes after exercise, dual-isotope single photon emission computed tomographic images were obtained simultaneously. After cross-talk compensation, the extent of ischemia and its localization were measured at both peak exercise and after exercise. Results When 64 patients with angiographically and scintigraphically proven ischemic heart disease were grouped by morphology of ST-segment depressions at 3 minutes after exercise, 38 patients with the downsloping type had ischemia localized mainly to the middle and basal levels as compared with the more rapid resolution of ischemia in 12 patients with horizontal type and 14 patients with no ischemic electrocardiographic response (apical level 18.4% [7/38], 8.3% [1/12], and 0% [0/14], P = not significant, middle level 47.4% [18/38], 16.7% [2/12], and 7.1% [1/14], P <.01, basal level 57.9% [22/38], 33.3% [4/12], and 14.3% [2/14], P <.02, respectively) independent of the extent or localization of any ischemia noted during exercise (all levels, P = not significant). Conclusion Electrocardiographic morphology during the recovery phase of exercise reflects the extent and localization of residual ischemia at that time independent of ischemic changes noted during exercise. (Am Heart J 2002;144:335-42.)

A novel quantitative dual-isotope method for simultaneous ventilation and perfusion lung SPET.

A quantitative dual-isotope single-photon emission tomography (SPET) technique for the assessment of lung ventilation (V) and perfusion (Q) using, respectively, technetium-99m labelled Technegas (140 keV) and indium-113m labelled macro-aggregated albumin (392 keV), is presented, validated and clinically tested in a healthy volunteer. In order to assess V, Q and V/Q distributions in quantitative terms, algorithms which correct for down scattering, photon scattering and attenuation, as well as an organ outline algorithm, were implemented. Scatter and down-scatter correction were made in the spatial domain by pixel-wise image subtraction of projection-dependent global scattering factors obtained from the energy domain. The attenuation correction was based on an iterative projection/back-projection method. All studies were made on a three-headed SPET system (Trionix) with medium-energy parallel-hole collimators. The set of input data for quantification was based on SPET acquisition of emission data in four separate energy windows, the associated cumulative energy spectra and transmission data. The attenuation correction routine as well as the edge detection algorithm utilized data from (99m)Tc transmission tomography. Attenuation data for (113m)In were obtained by linear scaling of the (99m)Tc attenuation maps. The correction algorithms were experimentally validated with a stack phantom system and applied on a healthy volunteer. The mean difference between the corrected SPET data of the dense stack lung phantom and those obtained from the corresponding scatter- and attenuation-"free" version was only 1.9% for (99m)Tc and 0.9% for (113m)In. The estimated fractional V/Q distribution in the 3-D lung phantom volume had its peak at V/Q=1, with a width (FWHM) of 0.31 due to noise, particularly in the (113m)In images, and to partial volume effects. For a healthy volunteer, the corresponding values were 0.9 and 0.35, respectively. This method allows accurate assessment of radionuclide distribution on a regional basis. For basic lung physiology and clinical practice, the method allows assessment of the global frequency functions of the V, Q and V/Q distributions.

Clinical value of triple-energy window scatter correction in simultaneous dual-isotope single-photon emission tomography with 123 I-BMIPP and 201 Tl

Clinical value of triple-energy window scatter correction in simultaneous dual-isotope single-photon emission tomography with 123 I-BMIPP and 201 Tl

Clinical value of triple-energy window scatter correction in simultaneous dual-isotope single-photon emission tomography with 123I-BMIPP and 201Tl.

To improve the image quality in simultaneous dual-isotope single-photon emission tomography (SPET) with iodine-123 labelled 15-(p-iodophenyl)-3-methylpentadecanoic acid (BMIPP) and thallium-201, we applied the triple-energy window method (TEW) for correction of the cross-talk and scatter artifact. Seventy-one patients with coronary artery disease were included. 201Tl cross-talk into the 123I acquisition window (group 1, n = 30) and 123I cross-talk into the 201Tl window (group 2, n = 41) were studied. In group 1, 123I images were first obtained (single-isotope images), followed by 201Tl injection and SPET acquisition using dual-isotope windows (dual-isotope images). In group 2, the order was reversed. The dual-isotope SPET images with and without TEW were compared with the single-isotope images. Qualitative evaluation was performed by scoring the segmental defect pattern. Detectability of the mismatched fatty acid metabolism on dual-isotope SPET was evaluated by receiver operating characteristic (ROC) curve analysis. Segmental defect pattern agreement between dual and corrected single images was significantly improved by TEW correction (P<0.01). The agreement was particularly improved in segments with absence of uptake. There was no significant difference between TEW-corrected dual-isotope SPET and corresponding single-isotope SPET with regard to either % defect count or background activity. Mismatched fatty acid metabolism depicted by dual-isotope SPET predicted abnormal wall motion more accurately with TEW than without TEW. With TEW, a practical method for scatter and cross-talk correction in clinical settings, simultaneous dual 123I-BMIPP/201Tl SPET is feasible for the assessment of myocardial perfusion/metabolism mismatch.

Simultaneous gallium-67 citrate and technetium-99m sestamibi SPET in a case of myocardial lymphoma: comparison with echocardiography before and after chemotherapy

A patient with diffuse large cell lymphoma involving the interventricular septum and the inferior ventricular wall was imaged with a simultaneous dual-isotope single-photon emission tomography (SPET) acquisition technique, using the radiotracers technetium-99m hexakis 2-methoxyisobutylisonitrile (sestamibi) and gallium-67 citrate, in conjunction with echocardiography, prior to and following the first course of chemotherapy. Simultaneous acquisition--with the advantage of displaying corresponding sets of SPET slices without any need for position correction--, supplemented by echocardiography, increased the accuracy of evaluation of the extent of disease and response to treatment.

Thallium and indium antimyosin dual-isotope single-photon emission tomography in acute myocardial infarction to identify patients at further ischaemic risk

Dual-isotope single-photon emission tomography (SPET) with indium-111 antimyosin and thallium-201 chloride was performed in 54 patients with acute myocardial infarction (AMI) to detect the location and extent of myocardial necrosis (antimyosin) and viable myocardium (201Tl). All patients underwent intravenous thrombolytic therapy with either streptokinase (1.5 million units/90 min) or tissue plasminogen activator (80 mg/90 min). Sensitivity in detecting MI was 91% (49/54 patients). With regard to dual-isotope SPET patterns, patients were divided into three groups: match, i.e. antimyosin uptake in segments with thallium defect (n = 8); mismatch, i.e. no uptake of either of the nuclides in corresponding segments (presence of perfusion abnormalities in the absence of antimyosin uptake) (n = 5); and overlap, i.e. thallium uptake in segments with uptake of antimyosin (n = 41). Coronary angiography and thallium exercise tests were performed in 40 and 45 patients, respectively, 5-14 days after MI. Exercise-induced ischaemia occurred in 66% of patients with overlap, 14% with match and 0% with mismatch (P < 0.05 for overlap vs other groups). If, however, major in-hospital complications (sudden cardiac death, severe arrhythmias; five overlap, three overlap in addition to match/mismatch, two match, two mismatch) were included in the statistical analysis, there was no significant difference between the three groups (P = NS). Thus, although the dual-isotope pattern "overlap" identifies a subgroup of patients with a substantial amount of residual viable tissue after MI and a high probability of exercise-induced ischaemia, this criterion is of limited value in assessing short-term prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)