Myocardial tracking, a new method to calculate ejection fraction with gated SPECT: validation with (201)Tl versus planar angiography.

Left ventricular ejection fraction (LVEF) and viability are essential variables for the prognosis of myocardial infarction and can be measured simultaneously by (201)Tl gated SPECT; however, most algorithms tend to underestimate LVEF. This study aimed to evaluate a new myocardial tracking algorithm, MyoTrack (MTK), for automatic LVEF calculation. METHODS: A rest/redistribution (20 min/4 h) (201)Tl gated SPECT protocol followed immediately by a (99m)Tc equilibrium radionuclide angiography (ERNA) was performed in 75 patients with history of myocardial infarction. Quality of myocardial uptake was evaluated from count statistics and automatic quantification of defect sizes and severities (CardioMatch). LVEFs were calculated both with Germano's quantitative gated SPECT (QGS) algorithm and with MTK. Briefly, the originality of this algorithm resides in the unique end-diastole segmentation, matching to a template and motion field tracking throughout the cardiac cycle. RESULTS: ERNA LVEF averaged 33% +/- 14%. QGS significantly underestimated this value at 20 min (30% +/- 13%, P < 0.001) and at 4 h (30% +/- 13%, P < 0.0001). By contrast, MTK did not miscalculate LVEF at 20 min (34% +/- 14%, probability value was not significant) though a similar underestimation occurred at 4 h (31% +/- 13%, P < 0.02). Individual differences between early and late gated SPECT values and differences between gated SPECT and ERNA values did not correlate with the extension of perfusion defects, count statistics, or heart rate. CONCLUSION: MTK algorithm accurately calculates LVEF on early/high-count images compared with ERNA [corrected], even in patients with severe perfusion defects, but tends to underestimate LVEF on delayed/low-contrast images, as other algorithms do.     

201Tl and 99mTc-MIBI gated SPECT in patients with large perfusion defects and left ventricular dysfunction: comparison with equilibrium radionuclide angiography.

Left ventricular ejection fraction (LVEF) is a major prognostic factor in coronary artery disease and may be computed by 99mTc-methoxyisobutyl isonitrile (MIBI) gated SPECT. However, 201Tl remains widely used for assessing myocardial perfusion and viability. Therefore, we evaluated the feasibility and accuracy of both 99mTc-MIBI and 201Tl gated SPECT in assessing LVEF in patients with myocardial infarction, large perfusion defects and left ventricular (LV) dysfunction. METHODS: Fifty consecutive patients (43 men, 7 women; mean age 61 +/- 17 y) with a history of myocardial infarction (anterior, 26; inferior, 18; lateral, 6) were studied. All patients underwent equilibnum radionuclide angiography (ERNA) and rest myocardial gated SPECT, either 1 h after the injection of 1110 MBq 99mTc-MIBI (n = 19, group 1) or 4 h after the injection of 185-203 MBq 201Tl (n = 31, group 2) using a 90 degrees dual-head camera. After filtered backprojection (Butterworth filter: order 5, cutoff 0.25 99mTc or 0.20 201Tl), LVEF was calculated from reconstructed gated SPECT with a previously validated semiautomatic commercially available software quantitative gated SPECT (QGS). Perfusion defects were expressed as a percentage of the whole myocardium planimetered by bull's-eye polar map of composite nongated SPECT. RESULTS: Gated SPECT image quality was considered suitable for LVEF measurement in all patients. Mean perfusion defects were 36% +/- 18% (group 1), 33% +/- 17% (group 2), 34% +/- 17% (group 1 + group 2). LVEF was underestimated using gated SPECT compared with ERNA (34% +/- 12% and 39% +/- 12%, respectively; P = 0.0001). Correlations were high (group 1, r= 0.88; group 2, r = 0.76; group 1 + group 2, r = 0.82), and Bland-Altman plots showed a fair agreement between gated SPECT and ERNA. The difference between the two methods did not vary as LVEF, perfusion defect size or seventy increased or when the mitral valve plane was involved in the defect. CONCLUSION: LVEF measurement is feasible using myocardial gated SPECT with the QGS method in patients with large perfusion defects and LV dysfunction. However, both 201Tl and 99mTc-MIBI gated SPECT similarly and significantly underestimated LVEF in patients with LV dysfunction and large perfusion defects.     

Accuracy of left ventricular ejection fraction determined by gated myocardial perfusion SPECT with Tl-201 and Tc-99m sestamibi: Comparison with first-pass radionuclide angiography

BACKGROUND: We compared estimates of left ventricular ejection fraction (LVEF) assessed by gated single photon emission computed tomography (SPECT), using both technetium-99m sestamibi and thallium-201, with those obtained by first-pass radionuclide angiography (FPRNA) in patients with a broad spectrum of LVEF and perfusion abnormalities. METHODS: Sixty-three patients were randomly selected to undergo a dual isotope gated SPECT study (rest Tl-201 followed by adenosine Tc-99m sestamibi scintigraphy). Studies were processed by use of the Cedars quantitative gated SPECT software. FPRNA was acquired during an intravenous bolus injection of Tc-99m sestamibi and processed with a commercially available software. RESULTS: The estimates of LVEF were similar (P = NS) with Tl-201 gated SPECT (54% +/- 15%), Tc-99m gated SPECT (54% +/- 16%), and FPRNA (54% +/- 12%). There was an excellent correlation between Tc-99m and Tl-201 gated SPECT (Pearson's r = 0.92, P < .0001). There were also good linear correlations between Tc-99m sestamibi gated SPECT and FPRNA (Pearson's r = 0.85, P < .0001), as well as between Tl-201 gated SPECT and FPRNA (Pearson's r = 0.84, P < .0001). In the 16 patients with LVEF < 50%, Tc-99m sestamibi gated SPECT and FPRNA (Pearson's r = 0.84, P < .0001) and Tl-201 gated SPECT and FPRNA (Pearson's r = 0.92, P < .0001) correlated well. CONCLUSION: LVEF can be accurately assessed by gated SPECT with either Tc-99m sestamibi or Tl-201 in properly selected patients with normal or depressed left ventricular function.     

Consideration of perfusion reserve in viability assessment by myocardial Tl-201 rest-redistribution SPECT: A quantitative study with dual-isotope SPECT

BACKGROUND: To optimize the use of thallium 201 rest-redistribution study in Tl-201/technetium 99m sestamibi dual-isotope single photon emission computed tomography (SPECT), the predictability of Tl-201 rest-redistribution for viable myocardium was examined according to the degree of perfusion reserve. METHODS AND RESULTS: Twenty patients with both unstable angina and left ventricular dysfunction were enrolled. Tl-201 rest-dipyridamole stress Tc-99m sestamibi gated SPECT/Tl-201 24-hour redistribution SPECT was performed before and 3 months after coronary artery bypass grafting. Through use of a 20-segment model, segmental stress perfusion, rest perfusion, and systolic thickening were quantified on gated SPECT by means of automatic quantitation software. Perfusion was expressed as the average percentage of maximal radioactivity uptake. To represent perfusion reserve, the perfusion difference score (PDS) was defined as rest perfusion minus stress perfusion. A low PDS indicated little or no inducible ischemia, and a high PDS indicated inducible ischemia. In dysfunctional myocardium, viability was defined by the improvement of thickening after coronary artery bypass grafting. The overall predictability of Tl-201 redistribution for viability was 0.709 of the area under the curve (AUC) in receiver operating characteristic analysis. With a cutoff of 7, predictability was significantly better in the low PDS group (AUC = 0.785) than in the high PDS group (AUC = 0.582). CONCLUSIONS: The predictability of Tl-201 rest-redistribution for viability differs according to perfusion reserve. It was more reliable for dysfunctional myocardium with persistent perfusion decrease. On the basis of the continuum hypothesis of chronic stunning and hibernation, we suggest that dysfunctional myocardium with persistent perfusion decrease should be assessed by Tl-201 redistribution SPECT.     

Left ventricular ejection fraction and volumes from gated single photon emission tomographic myocardial perfusion images: Comparison between two algorithms working in three-dimensional space

Objective. Two different algorithms operating in three-dimensional space, one dependent on surface detection developed at Cedars-Sinai Medical Center (CS) and another dependent on statistical parameters and developed at Stanford University Medical School (SU), were compared in the same patients to assess the left ventricular volumes and the left ventricular ejection fractions (LVEFs) from gated single-photon emission tomography (SPECT) myocardial perfusion images.Methods. Perfusion SPECT images gated in eight time bins were recorded in 40 patients with coronary artery disease 60 minutes after the injection of 925 MBq^99mTc-labeled tetrofosmin at rest. The LVEF values were validated against planar gated ^99mTc-labeled blood pool studies (ERNA).Results. The software success rates were 95% (38/40 patients) for CS and 100% for SU. Agreement between LVEFs measured with CS and SU and agreement between both methods and ERNA were excellent (LVEF_CS = 0.89LVEF_SU + 6.21, r = 0.93; LVEF_SU = 0.92LVEF_ERNA + 0.99, r = 0.94; and LVEF_CS = 0.88LVEF_ERNA + 4.58, r = 0.93). Bland-Altman plots showed that differences between LVEFs from SU and CS and from ERNA were similar across a wide range (20% to 80%) of LVEF values. No relationship between these differences and the severity of perfusion defects was observed. For left ventricular volumes, linear regression analysis showed an excellent correlation between both methods (end-diastolic volume R = 0.97 end-systolic volume R = 0.98), but systematically higher values were obtained with SU (p = 0.013).Conclusion. Measurements of LVEF obtained with CS and SU correspond well with those from the standard, ERNA, even in patients with severe perfusion defects. A close relationship is observed between SU and CS when left ventricular volumes are considered. Measurements of LVEF (and left ventricular volumes) should be considered as an integral part of myocardial perfusion studies whenever possible.     

Comparative performance of gated perfusion SPECT wall thickening, delayed thallium uptake, and F-18 fluorodeoxyglucose SPECT in detecting myocardial viability

To evaluate the comparative abilities of gated single photon emission computed tomography (SPECT) wall thickening, delayed thallium-201 (Tl-201) SPECT, and F-18 fluorodeoxyglucose (FDG) SPECT in detecting myocardial viability, 23 patients with previous myocardial infarction and clinically suspected viability were studied. Each patient had at least 1 extensive fixed perfusion defect on rest/stress technetium-99m sestamibi SPECT. A total of 41 major vascular territories had fixed defects. The mean (+/- 1 SD) left ventricular ejection fraction determined from gated perfusion SPECT was 26% +/- 11%. Wall thickening was assessed in a semiquantitative fashion by the regional increase in myocardial intensity during systole and was considered normal when a > or = 20% increase was observed. Tl-201 SPECT was acquired 4 hours after resting tracer injection was administered. Viability was considered present when regional defect Tl-201 count density, determined by quantitative analysis, was > 20% greater than that on the resting sestamibi scan. FDG SPECT was performed independently with a 10 mCi F-18 FDG dose after oral glucose loading was performed. A camera equipped with ultrahigh energy collimation was used. Quantitative criteria for viability were the same as for Tl-201. In the 23 patients viability within the fixed sestamibi defects was manifest by preserved wall thickening in 8 patients, delayed Tl-201 uptake in 10 patients, and FDG uptake in 18 patients. Nine major vascular territories with fixed defects were judged viable by wall thickening, 11 by Tl-201 SPECT, and 24 by FDG SPECT (P = .0009). We conclude that FDG SPECT demonstrates more evidence of myocardial viability than either gated sestamibi wall thickening or delayed Tl-201 SPECT.     

Comparison of contemporaneous left ventricular ejection fraction (LVEF) obtained from planar gated cardiac blood pool scans (GCBPS) and Tl-201 gated myocardial perfusion scans (MPS) using a novel solid state dedicated cardiac camera

Background

There is limited data on the concordance of left ventricular ejection fraction (LVEF) obtained via solid state dedicated cardiac cameras (SSD) and gated cardiac blood pool scans (GCBPS). This study aimed to examine the agreement of LVEF measured during GCBPS and Tl-201 myocardial perfusion scans (MPS) using SSD.

Methods

Seventy six patients were enrolled. Following stress MPS with 0.8 Mbq/kg (0.022 mCi/kg) Tl-201 and 8-frame gated rest studies after additional 15 Mbq (0.41 mCi) Tl-201, LVEFs were obtained using ECToolbox (ECT) and quantitative gated SPECT (QGS) software. Same day 16-frame planar GCBPS were performed. Interobserver variability was compared and LVEF results were compared using paired t tests, Pearson’s correlation and the differences of the LVEF were plotted against GCBPS values.

Results

For GCBPS, ECT and QGS, the mean (±SD) LVEF was 52% ± 14%, 61% ± 18% and 48% ± 19%, respectively. When compared to GCBPS, ECT and QGS, LVEFs had similar R values of 0.85 and 0.83, respectively, and mean differences [95% limits of agreement (LA)] of ?8.6% (?27.4% to +10.2%, P < .001) and 4.2% (?17.2% to +25.6%, P = .001), respectively.

Conclusion

While the LVEF obtained by ECT or QGS demonstrates a statistically significant correlation with GCBPS, they are significantly different and the wide 95% LA suggest that Tl-201 MPS LVEFs derived from either software package are not interchangeable with GCBPS results.     

Worsening of left ventricular ejection fraction induced by dipyridamole on Tl-201 gated myocardial perfusion imaging predicts significant coronary artery disease

BACKGROUND: Vasodilator stress on myocardial perfusion imaging has been found to induce ischemic stunning, which may present as transient worsening of left ventricular ejection fraction (LVEF) or regional wall motion abnormality. This study aimed to evaluate the significance of stress-induced worsening of LVEF in the diagnosis of coronary artery disease (CAD) on dipyridamole thallium 201 gated single photon emission computed tomography (SPECT). METHODS AND RESULTS: The study included 126 patients who underwent dipyridamole Tl-201 gated SPECT and coronary angiography within 3 months. Poststress and 4-hour rest images were obtained, and LVEF was calculated by use of automated software (QGS 3.0). A decrease in LVEF of 6% or greater from rest to poststress was considered significant, and this threshold was determined by the serial reproducibility assessment of Tl-201 gated SPECT. If worsening of LVEF was used as the criterion for detecting significant CAD (> or = 70% coronary stenoses in > or = 1 vessel), the sensitivity, specificity, positive predictive value, and negative predictive value were 35%, 93%, 90%, and 44%, respectively. CONCLUSION: Dipyridamole-induced worsening of LVEF, as shown by Tl-201 gated SPECT, is a valuable nonperfusion marker of significant CAD. Although the sensitivity of LVEF worsening in detecting significant CAD is only 35%, the specificity is as high as 93%.     

Detection and quantification of recent myocardial infarction: diagnostic value of multiecho multislice spin echo imaging

Thirty-four patients with documented transmural MI were studied with gated three echo, multislice MR imaging. In 12 patients MRI MI size was compared with CK release measurement, Tl-201 SPECT defect, and with Tc-99m LVEF. Infarct was visualised in 29/34 patients on 3rd echo images (18/34 on 2nd and 6/34 on 1st echo images). Mean MR infarct size (planimetered from 3rd echo images): 33.1 +/- 9% overestimated the SPECT defect (mean value of 23.8 +/- 15%). However, the overall correlation between MRI and Tl-201 sizing was significant: r = 0.82; p less than 0.001; SEE = 5.5%. The correlation with LVEF also appeared significant: r = -0.61; p less than 0.038.     

Assessment of left ventricular function by 201Tl SPECT using left ventricular cavity-to-myocardium count ratio

Equilibrium radionuclide angiography (ERNA) is the 'gold standard' for assessing left ventricular ejection fraction (LVEF). The aim of the study was to determine whether the left ventricular cavity-to-myocardium count ratio (LVCMR) from 201Tl myocardial single photon emission computed tomography (SPECT) correlated with LVEF assessed by ERNA. The study group included 159 consecutive patients (117 male, 42 female), aged 59+/-12 years, who underwent both 201Tl SPECT and ERNA at rest on the same day. The LVCMR was calculated from a mid-ventricular short axis slice on redistribution studies, using two regions of interest (ROIs). One ROI was placed in the centre of the left ventricular cavity (C) and the other was placed in the myocardium with maximum uptake (Mmax): LVCMR= (C/Mmax) x 100. The correlation between LVCMR and LVEF was r = 0.85 (y = 0.943x+5.002; P < 0.0001). The mean calculated values +/- 1 SD were LVCMR=54+/-16% and LVEF=52+/-15%. In conclusion, LVCMR from 201Tl SPECT studies was closely correlated with LVEF from ERNA studies and can be used to easily and rapidly estimate left ventricular function.     

Comparison of Tc-99m sestamibi and Tl-201 gated perfusion SPECT

BACKGROUND: To determine the interpretability of gated thallium-201 perfusion SPECT compared with that performed by use of technetium-99m sestamibi (MIBI), 33 patients with prior myocardial infarction were studied. Patients received 22 to 30 mCi (814 to 1110 MBq) MIBI at peak stress, and a 15-minute gated SPECT acquisition was begun 30 to 40 minutes thereafter. On a subsequent day gated Tl-201 SPECT was acquired for 15 minutes, 4 hours after a resting 3.5 mCi (130 MBq) injection. SPECT was performed over a 180-degree arc by use of a 90-degree angled 2-detector camera. RESULTS: Gated studies were interpreted independently by 4 experienced physicians. Study quality was graded (0 = uninterpretable to 4 = excellent). Wall motion (0 = normal to 2 = akinetic/dyskinetic) and wall thickening (0 = normal to 2 = absent) were graded for each of 10 segments viewed in orthogonal planes. Left ventricular ejection fraction (LVEF) was calculated by use of software thus far validated only for MIBI. The average count density of mid-ventricular end-diastolic short axis tomograms with sestamibi was 3.47 times greater than with thallium. Mean study quality was 3.4 for MIBI and 1.8 for thallium (P < 10(-6)). No gated MIBI SPECTs, but 2 gated thallium studies (6%) were judged uninterpretable. Among interpretable scans, interobserver agreement (Kendall statistic) in assessing wall motion was 0.73 for MIBI and 0.66 for thallium (P = .01). For assessing wall thickening, the Kendall statistic was 0.73 for MIBI and 0.69 for thallium (P = .05). Correlation (r) of LVEFs was 0.91, SEE = 6.4. CONCLUSIONS: We conclude that gated thallium SPECT is inferior to MIBI because of much poorer image quality and somewhat poorer interobserver agreement among experienced physicians. However, LVEF can be determined reliably from gated thallium SPECT.     

201Tl gated single photon emission computed tomographic myocardial perfusion imaging in the assessment of global and regional left ventricular function. Would it be favoured over equilibrium radionuclide angiography?

BACKGROUND: This study investigates the clinical performance of routine 201Tl gated single photon emission computed tomographic (201Tl GSPECT) myocardial perfusion imaging. Equilibrium radionuclide angiography (ERNA) was used as the standard for comparison. METHODS AND RESULTS: One hundred and seventy-two consecutive patients were submitted to both myocardial 201Tl GSPECT imaging, at stress and in redistribution, and ERNA. Left ventricular ejection fractions (LVEF) and regional wall motion were assessed from both stress and redistribution 201Tl GSPECT datasets, and from ERNA. Linear regression analysis showed a good correlation between LVEF calculated by ERNA and 201Tl GSPECT (r=0.73 at stress, r=0.75 in redistribution, P<0.0001). However, the 95% prediction intervals of 201Tl GSPECT LVEF from ERNA LVEF were wide (minimum 35.4% at stress and 33.2% in redistribution). Moreover, a difference in LVEF > or =10% between ERNA and 201Tl GSPECT was found in 26.4% of cases at stress and 28.6% of cases in redistribution. A fair agreement between ERNA and 201Tl GSPECT was found in regional wall motion assessment in segments with normal or mildly reduced tracer uptake (kappa=0.32 at stress and kappa=0.33 in redistribution). In segments with moderately to severely reduced tracer uptake, a moderate agreement was found in regional wall motion assessment between ERNA and 201Tl GSPECT (kappa=0.44 at stress and kappa=0.42 in redistribution). CONCLUSIONS: Left ventricular function may be misinterpreted in a significant proportion of patients if the calculation of LVEF is based on 201Tl GSPECT. Moreover, the evaluation of regional wall motion by 201Tl GSPECT appears unsatisfactory.     

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

PURPOSE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.     

Accuracy of the automated assessment of left ventricular function with gated perfusion SPECT in the presence of perfusion defects and left ventricular dysfunction: Correlation with equilibrium radionuclide ventriculography and echocardiography

BACKGROUND: Gated single photon emission computed tomography (SPECT) with automated methods allows the quantitative assessment of left ventricular function and perfusion; however, its accuracy must be defined for patients with large earlier infarctions and severe rest perfusion defects, in whom the estimation of endocardial and epicardial borders might be more difficult, even with automated edge-detection techniques. METHODS AND RESULTS: We prospectively compared the automated measurements of left ventricular ejection fraction (LVEF) and volumes from rest-injected gated Technetium 99m (Tc99m) perfusion SPECT with equilibrium radionuclide angiocardiography (ERNA) in 62 patients and the assessment of regional function with echocardiography in 22 patients. Forty-six patients had an earlier myocardial infarction (mean defect size, 34% of left ventricle; SD, 12.7%; range, 8% to 56%); 27 patients had large defects (> or = 20% of left ventricle; LVEF range, 8% to 75%). LVEF, as determined with Cedars-Sinai software (quantitative gated SPECT), correlated well with ERNA (r = 0.941; y = 1.003x + 1.15; P<.0001; SE of the estimate = 6.3%; mean difference -1.3% for LVEF) in the entire study population and in the subgroups of patients with an earlier infarction, severe defects, and large infarctions (> or = 20% of the left ventricle). A correlation existed between gated SPECT and ERNA volumes (r = 0.882, y = 1.040x - 14.7, P<.0001 for end-diastolic volume; r = 0.954, y = 1.147x - 13.9, P<.0001 for end-systolic volumes with the count-ratio technique), but with wider limits of agreement. The exact segmental score agreement between gated SPECT and echocardiography for regional function was 79.8% (281 of 352, kappa = 0.682). CONCLUSIONS: Automated gated SPECT provides an accurate assessment of ejection fraction and regional function, even in the presence of an earlier myocardial infarction with large perfusion defects and significant left ventricular dysfunction.     

Evaluation of viral myocarditis in children by radionuclide method

Evaluation of viral myocarditis is essential for the clinician to assess the prognosis. In this study, Tl-201 myocardial scintigraphy and Tc-99m gated cardiac blood pool scan were performed in 16 patients with myocarditis diagnosed by clinical symptoms and laboratory findings and these nuclear medicine techniques were followed up for 5 years. Exercise Tl-201 scintigraphy using a bicycle ergometer was performed in 8 patients by SPECT imaging. There were mild to severe persistent defects found in all cases (100%), but pressure rate products showed normal response. The Tl-201 defect ratio improved gradually, but did not change significantly. In the resting Tl-201 image one of 16 patients showed severe multifocal defects. LVEF increased significantly from 1 year to 5 years after onset, while RVEF measured by gated blood pool scans showed slight increases 3 years to 5 years after diagnosis. It was concluded that myocardial perfusion improved only incompletely. Cardiac function (LVEF and RVEF) improved gradually, and pressure rate products were normal. Myocarditis should therefore be followed up in order to assess the prognosis; moreover, the relationship of myocarditis to dilated cardiomyopathy needs to be further studied.     

Thallium-gated SPECT in patients with major myocardial infarction: effect of filtering and zooming in comparison with equilibrium radionuclide imaging and left ventriculography.

The effect of filtering and zooming on 201TI-gated SPECT was evaluated in patients with major myocardial infarction. METHODS: Rest thallium (TI)-gated SPECT was performed with a 90 degrees dual-head camera, 4 h after injection of 185 MBq 201TI in 32 patients (mean age 61 +/- 11 y) with large myocardial infarction (33% +/- 17% defect on bull's eye). End diastolic volume (EDV), end systolic volume (ESV) and left ventricular ejection fraction (LVEF) were calculated using a commercially available semiautomatic validated software. First, images were reconstructed using a 2.5 zoom, a Butterworth filter (order = 5) and six Nyquist cutoff frequencies: 0.13 (B5.13), 0.15 (B5.15), 0.20 (B5.20), 0.25 (B5.25), 0.30 (B5.30) and 0.35 (B5.35). Second, images were reconstructed using a zoom of 1 and a Butterworth filter (order = 5) (cutoff frequency 0.20 [B5.20Z1]) (total = 32 x 7 = 224 reconstructions). LVEF was calculated in all patients using equilibrium radionuclide angiocardiography (ERNA). EDV, ESV and LVEF were measured with contrast left ventriculography (LVG). RESULTS: LVEF was 39% +/- 2% (mean +/- SEM) for ERNA and 40% +/- 13% for LVG (P = 0.51). Gated SPECT with B5.20Z2.5 simultaneously offered a mean LVEF value (39% +/- 2%) similar to ERNA (39% +/- 2%) and LVG (40% +/- 3%), optimal correlations with both ERNA (r = 0.83) and LVG (r = 0.70) and minimal differences with both ERNA (-0.9% +/- 7.5% [mean +/- SD]) and LVG (1.1% +/- 10.5%). As a function of filter and zoom choice, correlation coefficients between ERNA or LVG LVEF, and gated SPECT ranged from 0.26 to 0.88; and correlation coefficients between LVG and gated SPECT volumes ranged from 0.87 to 0.94. There was a significant effect of filtering and zooming on EDV, ESV and LVEF (P < 0.0001). Low cutoff frequency (B5.13) overestimated LVEF (P < 0.0001 versus ERNA and LVG). Gated SPECT with 2.5 zoom and high cutoff frequencies (B5.15, B5.20, B5.25, B5.30 and B5.35) overestimated EDV and ESV (P < 0.04) compared with LVG. This volume overestimation with TI-gated SPECT in patients with large myocardial infarction was correlated to the infarct size. A zoom of 1 underestimated EDV, ESV and LVEF compared with a 2.5 zoom (P < 0.02). CONCLUSION: Accurate LVEF measurement is possible with TI-gated SPECT in patients with major myocardial infarction. However, filtering and zooming greatly influence EDV, ESV and LVEF measurements, and TI-gated SPECT overestimates left ventricular volumes, particularly when the infarct size increases.     

Assessment of left ventricular diastolic function with electrocardiography-gated myocardial perfusion SPECT: Comparison with multigated equilibrium radionuclide angiography

BACKGROUND: Technetium-labeled myocardial perfusion tracers allow the simultaneous assessment of myocardial perfusion and left ventricular function by electrocardiography (ECG)-gated myocardial perfusion single photon emission computed tomography (SPECT). This study evaluates left ventricular systolic and diastolic function by ECG-gated SPECT with the use of higher framing (32 frames per cardiac cycle) data acquisition. METHODS AND RESULTS: After receiving an injection of technetium 99m tetrofosmin, 48 patients with cardiac diseases were examined by ECG-gated myocardial perfusion SPECT with a 3-headed gamma camera. During gated data collection, 32 frames per cardiac cycle were acquired over 360 degrees in 60 steps, each of which consisted of 60 beats. Immediately thereafter, the 32 frames taken at each projection angle were combined into 16-frame and 8-frame data sets. Left ventricular end-diastolic volume (LVEDV, in milliliters), left ventricular end-systolic volume (LVESV, in milliliters), and left ventricular ejection fraction (LVEF, percentage) were automatically calculated from the 32-frame, 16-frame, and 8-frame gated data sets. Left ventricular time-volume curves from the 3 data sets were generated by Fourier curve fitting analysis with the use of 3 harmonics, and then peak filling rate (PFR, per second) was measured. Twenty-nine patients also underwent multigated equilibrium radionuclide angiography (ERNA) to determine the LVEF and PFR. Combining the 32-frame data into 16-frame and 8-frame data sets from the 48 patients generated a smaller LVEDV and a larger LVESV, and LVEF was significantly lower in accordance with the decreasing number of frames. Compared with ERNA studies (n = 29), the Bland-Altman method showed underestimated LVEFs and larger 95% limits of agreement in lower framing gated SPECT. CONCLUSIONS: Left ventricular functional parameters obtained from 32-frame gated SPECT correlated closely with those determined by ERNA studies. ECG-gated SPECT with 32-frame data can provide comprehensive information with which to evaluate many types of cardiac diseases.     

A comparison of Tl-201 stress-reinjection-prone SPECT and Tc-99m-sestamibi gated SPECT in the differentiation of inferior wall defects from artifacts

The frequency of false positive results obtained from the inferior myocardial region using single photon emission computed tomography (SPECT) myocardial perfusion scintigraphy is significantly higher than that obtained from other regions. Several methods, such as prone-position imaging, have been proposed to overcome this diagnostic problem. The aim of the present study was to compare the results of Tc-99m-sestamibi gated SPECT and Tl-201 prone SPECT in the differentiation of inferior wall artifacts from true defects. For this purpose, 38 subjects, whose coronary anatomies were documented on angiography, underwent same-day stress-rest Tc-99m-sestamibi gated SPECT and Tl-201 stress-reinjection-prone (whose standard supine images demonstrated fixed defects on the inferior wall) SPECT. Gated SPECT was performed by 8 frames per cycle acquisition over a 180 degree rotation on 30 projections. Four gated SPECT slices were obtained on mid-ventricular vertical long axis, horizontal long axis and apical and basal short axis planes, and displayed in cine-format. Both Tl-201 prone imaging and Tc-99m-sestamibi gated analysis increased the specificity of inferior wall disease detection remarkably from 54% to 85% and 46% to 82%, respectively (P<0.05). The difference between diagnostic accuracies was not significant (80% and 82%, respectively) (P > 0.05). The positive predictive values for true defects were 96% for Tl-201 prone imaging and 94% for Tc-99m-sestamibi gated imaging. Based on segmental analysis, the two modalities showed fair agreement (kappa = 0.44 for standard supine protocols, kappa = 0.46 for Tl-201 prone and Tc-99m-sestamibi gated SPECT). It can be concluded that Tc-99m-sestamibi gated SPECT, requiring only two-step acquisition, may potentially increase the test specificity for coronary artery disease (CAD) of the inferior wall as well as does Tl-201 stress-reinjection-prone SPECT. By giving functional information, it seems the most practical method in daily use for supplying the most extensive information about patients with suspected or known CAD.     

Intravenous dipyridamole thallium-201 SPECT imaging in patients with left bundle branch block

Tl-201 exercise imaging in patients with left bundle branch block (LBBB) has proven to be indeterminate for significant left anterior descending (LAD) coronary artery stenosis because of the presence of immediate septal perfusion defects with redistribution on delayed images in almost all cases. Tl-201 redistribution occurs regardless of the presence or absence of LAD stenosis. Nineteen patients having LBBB were evaluated with dipyridamole Tl-201 SPECT. Fourteen of these subjects had normal dipyridamole Tl-201 SPECT imaging. Three patients had normal coronary angiograms. None of the remaining 11 patients with normal dipyridamole Tl-201 SPECT images was found to have clinical coronary artery disease in a 5-11 month follow-up period. Five patients had abnormal septal perfusion. Four underwent coronary angiography. One had a significant LAD stenosis. The single patient with septal redistribution who refused to undergo coronary angiography died shortly thereafter of clinical coronary artery disease. This preliminary work suggests that dipyridamole Tl-201 SPECT may be more useful for excluding LAD stenosis in patients with LBBB than Tl-201 exercise imaging.     

Left ventricular ejection fraction from gated SPET myocardial perfusion studies: a method based on the radial distribution of count rate density across the myocardial wall

Left ventricular ejection fraction (LVEF) can be derived from gated single-photon emission tomographic (SPET) myocardial perfusion studies using either manual or edge detection techniques. In the presence of severe perfusion defects, however, difficulties may be encountered. In this article a method based on the assumption that the average position of the myocardial wall can be localized by means of statistical analysis of the distribution count density, and not on edge detection, is used to measure LVEF. SPET myocardial perfusion images, gated in eight time bins, were recorded in 50 patients 60 min after the injection of 925 MBq technetium-99m tetrofosmin. Masking of non-myocardial structures and thresholding resulted in images in which only myocardial walls had significant non-zero values. The distance of the wall relative to the centre of the cavity was calculated in the three-dimentional space as the first moment of the count rate distribution along radii originating in the centre of the cavity. LVEF was calculated using, for each time bin, the sum of the cube of all distances as an estimate of the cavity volume. The method required minimal operator interventions and was successful in all patients, including those with severe perfusion defects. Intraobserver and interobserver variability was excellent, with regression coefficients of 0.97 and standard deviations of 4.5% and 4.7%, respectively. For 30 patients, the measurements were validated against planar equilibrium radionuclide angiography (ERNA) that was obtained within an interval of 1 week. LVEF ranged from 12% to 88%. Agreement between the two methods was excellent (LVEFE_ERNA=1.05+0.92 LVEF_GSPET,r=0.93,P=0.023, SEE=7.06). The Bland-Altman analysis did not show any apparent trend in the differences between ERNA and gated SPET over a wide range of ejection fractions. The standard deviation of the differences was 3.1%. In addition no relationship was found between the two methods and the severity of perfusion defects. In conclusion, accurate measurements of LVEF are obtained from gated SPET perfusion images using a method based on statistical analysis of the count rate density. This method did not deteriorate even in the presence of severe perfusion defects and could therefore be used in following patients after myocardial infarction.