Validation of left ventricular volume measurements by gated SPECT 99mTc-labeled sestamibi imaging

Assessment of four different cardiac softwares for evaluation of LVEF with CZT-SPECT vs CMR in 48 patients with recent STEMI

PURPOSE

To compare, vs CMR, four softwares: quantitative gated SPECT (QGS), myometrix (MX), corridor 4DM (4DM), and Emory toolbox (ECTb) to evaluate left ventricular ejection fraction (LVEF), end-systolic (ESV), and end-diastolic volumes (EDVs) by gated MPI CZT-SPECT.

METHODS

48 patients underwent MPI CZT-SPECT and CMR 6 weeks after STEMI, LV parameters were measured with four softwares at MPI CZT-SPECT vs CMR. We evaluated (i) concordance and correlation between MPI CZT-SPECT and CMR, (ii) concordance MPI CZT-SPECT/CMR for the categorical evaluation of the left ventricular dysfunction, and (iii) impacts of perfusion defects > 3 segments on concordance.

RESULTS

LVEF: LCC QGS/CMR = 0.81 [+ 2.2% (± 18%)], LCC MX/CMR = 0.83 [+ 1% (± 17.5%)], LCC 4DM/CMR = 0.73 [+ 3.9% (± 21%)], LCC ECTb/CMR = 0.69 [+ 6.6% (± 21.1%)]. ESV: LCC QGS/CMR = 0.90 [- 8 mL (± 40 mL)], LCC MX/CMR = 0.90 [- 9 mL (± 36 mL)], LCC 4DM/CMR = 0.89 [+ 4 mL (± 45 mL)], LCC ECTb/CMR = 0.87 [- 3 mL (± 45 mL)]. EDV: LCC QGS/CMR = 0.70 [- 16 mL (± 67 mL)], LCC MX/CMR = 0.68 [- 21 mL (± 63 mL], LCC 4DM/CMR = 0.72 [+ 9 mL (± 73 mL)], LCC ECTb/CMR = 0.69 [+ 10 mL (± 70 mL)].

CONCLUSION

QGS and MX were the two best-performing softwares to evaluate LVEF after recent STEMI.

Agreement between left ventricular ejection fraction assessed in patients with gated IQ-SPECT and conventional imaging

BACKGROUND

The aim of the study was to assess the agreement between the left ventricular ejection fraction (LVEF) values obtained with IQ-SPECT and those obtained with a conventional gamma camera equipped with low-energy high-resolution (LEHR), considered as the method of reference.

METHODS

Gated-stress MPI using 99mTc-tetrofosmin was performed in 55 consecutive patients. The patients underwent two sequential acquisitions (Method A and B) performed on Symbia-IQ SPECT with different acquisition times and one (Method C) on a Ecam SPECT equipped with LEHR collimators. The values of the different datasets were compared using the Bland-Altman analysis method: the bias and the limits of agreement (LA) were estimated in a head-to-head comparison of the three protocols.

RESULTS

In the (Method A-Method C) comparison for LVEF, the bias was 3.8% and the LAs ranged from - 9.3% to 16.8%. The agreement was still lower between Method B and C, whilst only slightly improved when Methods A and B were compared.

CONCLUSIONS

The wide amplitude in LA intervals of about 30% indicates that IQ and LEHR GSPECT are not interchangeable. The values obtained with IQ-SPECT should only be used with caution when evaluating the functional state of the heart.

The correlation between myocardial perfusion scintigraphy and three-dimensional echocardiography in ejection fraction and cardiac volumes for determination of the nearest filtering parameters

End-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) are cardiac volumes that have crucial roles in diagnosis of cardiovascular diseases (CVD) in patients. There are differences between these mentioned parameters in echocardiography (Echo) and myocardial perfusion scintigraphy (MPS) in clinical practice. In this study, we determined the nearest filtering parameters in the analysis of MPS data in comparison with three-dimensional echocardiography (3DE). All of patients were in this study, and 3DE and MPS were performed for all patients at rest phase in the same day. MPS images were analyzed through quantitative gated single photon emission computer tomography (SPECT) software with Butterworth filter which was a fixed order (order = 5) and variable cutoffs (COs) of 0.3, 0.35, 0.4, 0.45, and 0.5. The EDV, ESV, and EF values were measured by 3DE and MPS and compared. Based on the above different COs, the ESVs of MPS were 15.5 ± 18 mL, 18 ± 20 mL, 21 ± 22.5 mL, 22 ± 23 mL, and 22.5 ± 23.5 mL, respectively, while ESV of 3DE was 44.4 ± 23.5 mL. It was observed as a significant difference between MPS and 3DE for ESV. The EDVs of MPS were 61.3 ± 24.5 ml, 64 ± 26.5 ml, 68 ± 29.5 ml, 72 ± 31 ml, and 76 ± 32.2 ml, respectively, while EDV of 3DE was 105 ± 30 ml, which was significantly different between two methods. The EFs of MPS were 79% ± 14%, 76% ± 13%, 73.5% ± 12%, 73.5% ± 11%, and 74% ± 11%, respectively. The EF of 3DE was 58.4% ± 10% ml. It was statistically significant difference in values of EF between SPECT analysis parameters and 3DE. It was interesting when the COs increased from 0.3 to 0.5; the cardiac volumes increased while the EF decreased. The measured ESV and EDV values were lower in females than males while the EFs of females were higher than males. Finally, we demonstrate that the nearest Cos for measuring of EF and cardiac volumes for analysis of MPS data in comparison with 3DE are 0.45 and 0.5, respectively.

Optimal thallium-201 dose in cadmium-zinc-telluride SPECT myocardial perfusion imaging

BACKGROUND

We aimed to determine the optimal thallium 201 chloride (thallium-201) dose using a novel ultrafast cardiac gamma camera with cadmium-zinc-telluride (CZT) solid-state semiconductor detectors (D-SPECT).

METHODS AND RESULTS

The optimal thallium-201 dose for obtaining left ventricular (LV) myocardial counts was determined from a phantom study. Consecutive 292 patients underwent stress myocardial perfusion imaging with a thallium-201 injection. Stress test comprised exercise or pharmacological (adenosine) provocation. We calculated an optimal thallium-201 dose that resulted in better LV myocardial counts during 6 minutes of acquisition time. We corrected the respective values according to the patient's age, sex, body mass index (BMI), and type of stress test. The lowest thallium-201 dose for obtaining acceptable imaging was 1.2 million counts. Radiopharmaceutical doses showed a positive correlation with the patient's age (P < .001), sex (P = .012), BMI (P < .001), and type of stress test (P < .001). Multivariate analysis revealed that the patient's BMI and the type of stress test were statistically significant factors for determining the correct radiopharmaceutical dose (P < .001 for both).

CONCLUSIONS

For clinical use of the CZT SPECT system, the optimal individual thallium-201 doses can be determined based on the patient's BMI and type of stress test.

Comparison of conventional and cadmium-zinc-telluride single-photon emission computed tomography for analysis of thallium-201 myocardial perfusion imaging: an exploratory study in normal databases for different ethnicities

The aim of this study was to clarify the differences in thallium-201-chloride (thallium-201) myocardial perfusion imaging (MPI) scans evaluated by conventional anger-type single-photon emission computed tomography (conventional SPECT) versus cadmium-zinc-telluride SPECT (CZT SPECT) imaging in normal databases for different ethnic groups. MPI scans from 81 consecutive Japanese patients were examined using conventional SPECT and CZT SPECT and analyzed with the pre-installed quantitative perfusion SPECT (QPS) software. We compared the summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) for the two SPECT devices. For a normal MPI reference, we usually use Japanese databases for MPI created by the Japanese Society of Nuclear Medicine, which can be used with conventional SPECT but not with CZT SPECT. In this study, we used new Japanese normal databases constructed in our institution to compare conventional and CZT SPECT. Compared with conventional SPECT, CZT SPECT showed lower SSS (p < 0.001), SRS (p = 0.001), and SDS (p = 0.189) using the pre-installed SPECT database. In contrast, CZT SPECT showed no significant difference from conventional SPECT in QPS analysis using the normal databases from our institution. Myocardial perfusion analyses by CZT SPECT should be evaluated using normal databases based on the ethnic group being evaluated.

Electrocardiographic and scintigraphic evaluation of patients with subclinical hyperthyroidism during workout

Subclinical hyperthyroidism (sHT) was found to be associated with elevated heart rate, blood pressure and increased risk of extrasystoles. However, the full clinical relevance of morphological and functional implications of sHT on the cardiovascular system is still a matter of debate. The aim of the study was to prospectively assess the influence of endogenous sHT on exercise capacity and cardiac function during workout with the use of exercise electrocardiography (ExECG) and perfusion scintigraphy. The studied group consisted of 44 consecutively recruited patients diagnosed with sHT. In all patients, ExECG, followed by post-exercise myocardial perfusion imaging, was performed. Both ExECG and scintigraphy were performed twice-in the state of sHT and after euthyroidism was restored. An average time period of exercise test was significantly longer in the state of euthyroidism than in sHT. An average oxygen consumption during exercise test was also higher after euthyroidism was achieved when compared to sHT. The end-diastolic and end-systolic volume indexes, stroke volume index and cardiac index were significantly larger in patients with sHT if compared values achieved after euthyroidism restoration. Stroke volume index was negatively correlated with TSH, and positively with free thyroid hormones values in the state of sHT, before euthyroidism was achieved. Cardiac index was positively correlated with free thyroid hormones levels. The obtained results indicate worse physical capacity in subjects with sHT and improvement of several parameters assessed during ExECG and perfusion scintiscan after therapy. Observed changes might reflect the mechanism of the deleterious effect exerted by sHT on the heart.

Left ventricular remodeling after late revascularization correlates with baseline viability

The ideal management of stable patients who present late after acute ST-elevation myocardial infarction (STEMI) is still a matter of conjecture. We hypothesized that the extent of improvement in left ventricular function after successful revascularization in this subset was related to the magnitude of viability in the infarct-related artery territory. However, few studies correlate the improvement of left ventricular function with the magnitude of residual viability in patients who undergo percutaneous coronary intervention in this setting. In 68 patients who presented later than 24 hours after a confirmed first STEMI, we performed resting, nitroglycerin-enhanced, technetium-99m sestamibi single-photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) before percutaneous coronary intervention, and again 6 months afterwards. Patients whose baseline viable myocardium in the infarct-related artery territory was more than 50%, 20% to 50%, and less than 20% were divided into Groups 1, 2, and 3 (mildly, moderately, and severely reduced viability, respectively). At follow-up, there was significant improvement in end-diastolic volume, end-systolic volume, and left ventricular ejection fraction in Groups 1 and 2, but not in Group 3. We conclude that even late revascularization of the infarct-related artery yields significant improvement in left ventricular remodeling. In patients with more than 20% viable myocardium in the infarct-related artery territory, the extent of improvement in left ventricular function depends upon the amount of viable myocardium present. The SPECT-MPI can be used as a guide for choosing patients for revascularization.

Relevance of early poststress variation in left ventricular function studied by gated-SPECT: evaluation in different clinical settings and relationship with angiography results

BACKGROUND

Stress-induced ischemia may cause a decrease in left ventricular ejection fraction (EF). We evaluated the variation in early postexercise EF (S-EF) compared with rest EF (R-EF) in different clinical settings to detect ventricular dysfunction. We also correlated ventricular dysfunction with an angiographic score, the Syntax score, in a subgroup of ischemic patients.

MATERIALS AND METHODS

Gated-SPECT images were acquired 12 min after exercise stress and at rest in 1481 patients. Patients were classified as controls, negative for ischemia, mildly ischemic, moderately/severely ischemic, necrotic, and necrotic with ischemia. Mean end-diastolic volume, end-systolic volume, and EF were compared in each group. The ratio between stress to rest EF was indicated as the functional score. Angiography results were collected for 55% of moderately/severely ischemic patients. Sixty-one angiographies were also completed with Syntax score evaluation.

RESULTS

In negative, necrotic, and mildly ischemic patients no differences were found between S-EF and R-EF. An opposite trend was observed in moderately/severely ischemic patients with a decrement of S-EF compared with R-EF (54.80±11.33 vs. 57.79±11.14; P<0.0001). Coronary artery disease was confirmed by angiography in 93% of moderately/severely ischemic patients. In 61 patients who underwent Syntax score evaluation, significant correlation was observed with functional score. Significant decrease in functional score was found in patients with coronary artery bypass graft indication compared with patients with percutaneous coronary intervention or medical indication.

CONCLUSION

Early poststress gated-SPECT acquisition allows the detection of ventricular dysfunction in moderately/severely ischemic disease and provides additional information when directing patients to angiography and revascularization.

Gated F-18 FDG PET for assessment of left ventricular volumes and ejection fraction using QGS and 4D-MSPECT in patients with heart failure: a comparison with cardiac MRI

Purpose

Ventricular function is a powerful predictor of survival in patients with heart failure (HF). However, studies characterizing gated F-18 FDG PET for the assessment of the cardiac function are rare. The aim of this study was to prospectively compare gated F-18 FDG PET and cardiac MRI for the assessment of ventricular volume and ejection fraction (EF) in patients with HF.

Methods

Eighty-nine patients with diagnosed HF who underwent both gated F-18 FDG PET/CT and cardiac MRI within 3 days were included in the analysis. Left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV), and EF were obtained from gated F-18 FDG PET/CT using the Quantitative Gated SPECT (QGS) and 4D-MSPECT software.

Results

LV EDV and LV ESV measured by QGS were significantly lower than those measured by cardiac MRI (both P<0.0001). In contrast, the corresponding values for LV EDV for 4D-MSPECT were comparable, and LV ESV was underestimated with borderline significance compared with cardiac MRI (P = 0.047). LV EF measured by QGS and cardiac MRI showed no significant differences, whereas the corresponding values for 4D-MSPECT were lower than for cardiac MRI (P<0.0001). The correlations of LV EDV, LV ESV, and LV EF between gated F-18 FDG PET/CT and cardiac MRI were excellent for both QGS (r = 0.92, 0.92, and 0.76, respectively) and 4D-MSPECT (r = 0.93, 0.94, and 0.75, respectively). However, Bland-Altman analysis revealed a significant systemic error, where LV EDV (−27.9±37.0 mL) and ESV (−18.6±33.8 mL) were underestimated by QGS.

Conclusion

Despite the observation that gated F-18 FDG PET/CT were well correlated with cardiac MRI for assessing LV function, variation was observed between the two imaging modalities, and so these imaging techniques should not be used interchangeably.

Gated SPECT in assessment of regional and global left ventricular function: an update

Gated myocardial perfusion SPECT (GSPECT) is a major clinical tool, widely used for performing myocardial perfusion imaging procedures. In this review, we have presented the fundamentals of GSPECT and the ways in which the functional measurements it provides have contributed to the emergence of myocardial perfusion SPECT in its important role as a major tool of modern cardiac imaging. GSPECT imaging has shown unique capability to provide accurate, reproducible and operator-independent quantitative data regarding myocardial perfusion, global and regional systolic and diastolic function, stress-induced regional wall-motion abnormalities, ancillary markers of severe and extensive disease, left ventricular geometry and mass, as well as the presence and extent of myocardial scar and viability. Adding functional data to perfusion provides an effective means of increasing both diagnostic accuracy and reader's confidence in the interpretation of the results of perfusion scans. Assessment of global and regional LV function has improved the prognostic power of myocardial perfusion SPECT and has been shown in a large registry to add to the perfusion assessment in predicting benefit from revascularization.

Comparison of software programs for the assessment of left ventricular ejection fraction using 99mTc-tetrofosmin-gated SPECT/CT: correlation with equilibrium radionuclide ventriculography in the Indian population

OBJECTIVE

The goal of this study was to compare Emory Cardiac Toolbox (ECTb), quantitative gated SPECT (QGS), four-dimensional single photon emission computed tomography (4D-MSPECT) and Myometrix cardiac software programs for the assessment of left ventricular ejection fraction (LVEF) using 99mTc-tetrofosmin-gated SPECT/CT [myocardial perfusion SPECT (MPS)] and correlate them with the LVEF values derived from equilibrium radionuclide ventriculography (ERNV) in patients with known/suspected coronary artery disease (CAD).

MATERIALS AND METHODS

A total of 109 patients (80 men, 29 women) were recruited into the study. Fifty-five patients had known CAD and 54 were referred with suspicion of CAD. All the patients underwent ERNV and MPS as per the standard protocol. ERNV was processed using the vendor-provided 'EF analysis' and gated MPS was processed using individual software programs.

RESULTS

The mean LVEF on ERNV was 47.9 ± 15.5%. The mean LVEF values for ECTb, QGS, 4D-MSPECT and Myometrix were 51.5 ± 19.6, 51.0 ± 18.6, 57.1 ± 19.3 and 49.7 ± 19%, respectively. On correlation analysis, a very strong positive correlation was observed between LVEF values derived by ERNV and those derived by the MPS software programs: ECTb (r=0.842, P<0.0001), QGS (r=0.835, P<0.0001), 4D-MSPECT (r=0.830, P<0.0001) and Myometrix (r=0.875, P<0.0001). Significant correlation was also seen for LVEFs among the four software programs. Normal cutoff values for ejection fraction on ECTb, QGS, 4D-MSPECT and Myometrix were 56, 52, 54 and 51%, respectively, using a 50% or more cutoff value on ERNV.

CONCLUSION

A strong correlation was observed among ECTb, QGS, 4D-MSPECT and Myometrix software programs when compared with ERNV and also between them for assessment of LVEF. However, there are subtle differences in the objective values of ejection fraction generated by individual software, which must be taken into account for clinical studies.

Gated SPECT offers improved interobserver agreement compared with echocardiography

PURPOSE

Left ventricular ejection fraction (EF) is a powerful predictor of prognosis in coronary artery disease. The purpose of the present study was to measure interobserver differences for gated SPECT (GSPECT) software and echocardiography, and to compare these modalities regarding left ventricular volumes and EF.

MATERIALS AND METHODS

Eighty-four patients scheduled for nuclear imaging underwent a 1-day GSPECT with Tc-99m-tetrofosmin. Images were processed by 2 raters who calculated volumes and EF using Cedar-Sinai quantitative gated-SPECT (QGS), Emory Cardiac Toolbox (ECT), and 4D-MSPECT of the University of Michigan. Echocardiographic volumes were measured by 2 raters. Interobserver reliability was assessed by intraclass correlation coefficient (ICC). Differences in volumes and EF between echocardiography and GSPECT were compared with t-tests.

RESULTS

ICC was 0.61 for echocardiography, 0.94 for QGS, 0.88 for ECT, and 0.91 for 4D-MSPECT (P < 0.0001 compared with echocardiography). For small ventricles (ESV ≤30 mL), ICC was 0.58 for echocardiography and 0.90 for QGS (P = 0.008 compared with echocardiography); 0.77 and 0.73 for ECT and 4D-MSPECT, respectively (P = ns). End-diastolic and end-systolic volumes were significantly larger with GSPECT than with echocardiography, also echocardiographic ejection fraction was significantly different from GSPECT.

CONCLUSIONS

There is better interobserver reliability in GSPECT as compared with echocardiography, and QGS seems more robust in this study especially when it comes to small ventricles.

Myocardial perfusion imaging analysis in patients with regurgitant valvular heart disease

BACKGROUND/AIM

We noticed that there was decreased correlation of the findings from myocardial perfusion imaging (MPI) and cardiac catheterization (CATH) in patients with mitral regurgitation (MR) and aortic regurgitation (AR) compared to patients without valve disease.

METHODS

Through a systematic review of MPI records at the Harry S. Truman Memorial Veterans' Hospital between 1998 and 2008, we identified 58 patients with at least moderate MR or AR by echocardiogram who underwent cardiac catheterization within 6 months of the MPI study. A control group was formulated with 60 patients who did not have significant MR or AR on echocardiogram and who had both MPI and CATH. Correlation between MPI and CATH was graded as complete, partial, or absent.

RESULTS

Correlation between MPI and CATH was lower in the valve disease patients (study group) when compared to controls. Correlation was complete in 76% of study patients and 90% of controls, partial in 15% of study patients and 5% of controls, and absent in 9% of study patients and 5% of controls. Differences between the groups were significant (P < .05).

CONCLUSIONS

Patients with regurgitant valvular heart disease may have myocardial perfusion abnormalities that are not associated with angiographic critical coronary stenosis.

The Occluded Artery Trial (OAT) Viability Ancillary Study (OAT-NUC): influence of infarct zone viability on left ventricular remodeling after percutaneous coronary intervention versus optimal medical therapy alone

BACKGROUND

The Occluded Artery Trial (OAT) showed no difference in outcomes between percutaneous coronary intervention (PCI) versus optimal medical therapy (MED) in patients with persistent total occlusion of the infarct-related artery 3 to 28 days post-myocardial infarction. Whether PCI may benefit a subset of patients with preservation of infarct zone (IZ) viability is unknown.

METHODS AND RESULTS

The OAT nuclear ancillary study hypothesized that (1) IZ viability influences left ventricular (LV) remodeling and that (2) PCI as compared with MED attenuates adverse remodeling in post-myocardial infarction patients with preserved viability. Enrolled were 124 OAT patients who underwent resting nitroglycerin-enhanced technetium-99m sestamibi single-photon emission computed tomography (SPECT) before OAT randomization, with repeat imaging at 1 year. All images were quantitatively analyzed for infarct size, IZ viability, LV volumes, and function in a core laboratory. At baseline, mean infarct size was 26% ± 18 of the LV, mean IZ viability was 43% ± 8 of peak uptake, and most patients (70%) had at least moderately retained IZ viability. There were no significant differences in 1-year end-diastolic or end-systolic volume change between those with severely reduced versus moderately retained IZ viability, or when compared by treatment assignment PCI versus MED. In multivariable models, increasing baseline viability independently predicted improvement in ejection fraction (P = .005). There was no interaction between IZ viability and treatment assignment for any measure of LV remodeling.

CONCLUSIONS

In the contemporary era of MED, PCI of the infarct-related artery compared with MED alone does not impact LV remodeling irrespective of IZ viability.

Interassay reproducibility of myocardial perfusion gated SPECT in patients with atrial fibrillation

AIM

The aim of this study was to assess interassay reproducibility of myocardial perfusion gated-SPECT for calculation of end-diastolic volume (EDV), end-systolic volume (ESV), and left ventricular ejection fraction (LVEF) in patients with atrial fibrillation (AF).

METHODS

One hundred and fifteen consecutive patients with AF from three participating hospitals (mean age 68.9 years, 39 women) were included in the study. All patients underwent two image gated acquisitions at rest with a 30 minute interval between them. Quantitative data were obtained using the QGS and ECT software algorithms.

RESULTS

Heart rate was similar in both studies: 74.94 +/- 15.2 vs 73.03 +/- 15.57. QGS yielded an LVEF of 54.4%/53.8%, an EDV of 100 mL/101.5 mL, and an ESV of 51 mL/52.3 mL; and ECT showed an LVEF of 63.6%/62.9%, an EDV of 125.8 mL/127.4 mL and ESV of 54.1 mL/56.3 mL. Correlation between the two acquisitions was high (>0.948) for both methods for LVEF, EDV and ESV. Regression and Bland-Altman graphics showed a good agreement between all parameters. Interassay variation coefficients for each method (QGS/ECT) were 5.29% vs 4.83% for LVEF, 4.94% vs 5.17% for EDV, and 9.94% vs 12.78% for ESV.

CONCLUSIONS

Interassay reproducibility of LVEF and EDV with gated-SPECT in patients with AF is good, whereas for ESV it is suboptimal, particularly when ESV is small.

Myocardial perfusion, function, and dyssynchrony in patients with heart failure: baseline results from the single-photon emission computed tomography imaging ancillary study of the Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing (HF-ACTION) Trial

BACKGROUND

There are currently limited data on the relationships between resting perfusion abnormalities, left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) functional class, and exercise capacity as defined by peak VO(2) and 6-minute walk test in patients with heart failure (HF) and reduced LVEF. Furthermore, the association between resting perfusion abnormalities and left ventricular dyssynchrony is currently unknown. This article addresses the Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing (HF-ACTION) gated SPECT imaging (gSPECT) substudy baseline results.

METHODS

HF-ACTION was a multicenter, randomized controlled trial of aerobic exercise training versus usual care in 2,331 stable patients with LVEF of < or = 35% and NYHA class II to IV HF symptoms treated with optimal medical therapy. Subjects enrolled in the HF-ACTION substudy underwent resting Tc-99m tetrofosmin gSPECT at baseline (n = 240). Images were evaluated for extent and severity of perfusion abnormalities using a 17-segment and a 5-degree gradation severity score (summed rest score [SRS]). Left ventricular function and dyssynchrony were assessed using validated available commercial software.

RESULTS

The average age of patients enrolled was 59, 69% were male, 63% were white, and 33% were African American. Of the 240 participants, 129 (54%) were ischemic and 111 (46%) were nonischemic in etiology. The median LVEF by gSPECT for the entire cohort was 26%. Among the nuclear variables, there was a modest correlation between LVEF and SRS (r = -0.31, P < .0001) and there were stronger correlations between phase SD and SRS (r = 0.66, P < .0001) as well as phase SD and LVEF (r = -0.50, P < .0001). Patients with NYHA class III symptoms had more severe and significant degrees of dyssynchrony (median phase SD 54 degrees ) than those with NYHA class II symptoms (median phase SD 39 degrees, P = .001). Patients with an ischemic etiology had a higher SRS (P < .0001) and significantly more dyssynchrony (P < .0001) than those who were nonischemic. However, there was no difference in LVEF or objective measures of exercise capacity between these groups. With respect to peak VO(2), there was a weak correlation with LVEF (r = 0.18, P = .006) and no correlation with SRS (r = -0.04, P = 0.59) or with dyssynchrony (r = -0.13, P = .09). A weak but statistically significant correlation between SRS and 6-minute walk was observed (r = -0.15, P = .047).

CONCLUSIONS

Gated SPECT imaging can provide important information in patients with HF due to severe LV dysfunction including quantitative measures of global systolic function, perfusion, and dyssynchrony. These measurements are modestly but significantly related to symptom severity and objective measures of exercise capacity.

[Quantification of left ventricular function and mass in dual-source CT (DSCT).]

OBJECTIVES

To evaluate the interobserver agreement in quantifying left ventricular function and mass and to assess the accuracy of conventional manual contour tracing compared to semiautomatic segmentation analysis software.

MATERIAL AND METHODS

Twenty consecutive subjects who underwent cardiac DSCT with retrospective ECG-gating were included. Two different multiphase image reconstructions were done in 5% steps throughout the entire cardiac cycle (0-95% of the R-R interval) with effective slice thickness of 1mm in the axial plane and 8mm in the short-axis orientation. Left ventricular function and mass were calculated by two independent observers, tracing endocardial and epicardial borders manually and using a semiautomatic software tool (Circulation II, Siemens). Ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), cardiac output (CO), and myocardial mass were evaluated by two independent observers blind to each other's assessments. The interobserver agreement and the reliability of the different segmentation methods were calculated. The time required for manual contouring and semiautomatic contour tracing was also registered.

RESULTS

We found an excellent correlation (r>0.94; p<0.05) between the two independent observers for the quantification of left ventricular function and mass. Left ventricular functional parameters derived from semiautomatic contour software and conventional manual tracing method were not significantly different (p>0.05). The semiautomatic contour detection algorithm overestimated LV mass significantly compared with the manual contouring method (mean difference 29.45+/-1.64g; p<0.05). The time needed to calculate these parameters with the semiautomatic tool was significantly lower (248.85+/-99.8s) than with manual contouring (452.7+/-73.92s) (p<0.05).

CONCLUSIONS

Interobserver agreement for quantifying left ventricular function and mass using DSCT is excellent. Despite overestimating left ventricular mass, the semiautomatic software tool allows cardíac parameters to be quantified with the same reliability as the conventional manual method in half the time.

Assessment of cardiac parameters using gated myocardial perfusion and echocardiography in children

Echocardiographic and radionuclide techniques are the most common techniques currently used to assess ventricular function. The aim of our study was to assess the performance of two well-known methods for analysis of gated myocardial perfusion with comparison to echocardiography in children. We analyzed the data from 64 children referred for myocardial perfusion scintigraphy. All underwent echocardiography and stress gated myocardial perfusion scintigraphy, except 5 who had only rest scintigraphy. We calculated the left ventricular volumes and ejection fractions. The parametric information from the echocardiographic reports was compared to the data obtained using gated myocardial perfusion. The reliability between the quantitative gated scintigraphy, the Emory cardiac toolbox, and echocardiography for end-diastolic and end-systolic volumes and ejection fractions in studies performed at rest were calculated at 0.85, 0.86 and 0.97, respectively using Cronbach's alpha coefficient. The values in stress studies were 0.83, 0.86 and 0.90, respectively. There was a high correlation, with r more than 0.88, between quantitative gated scintigraphy and the Emory cardiac toolbox for ejection fractions, and end-diastolic and end-systolic volumes, in studies performed both under stress and at rest. Weak correlation was observed between quantitative gated scintigraphy and the Emory cardiac toolbox compared to echocardiography, especially when considering ventricular volumes in stress studies. Although high correlation was observed between quantitative gated scintigraphy and the Emory cardiac toolbox, comparison with echocardiography showed poor agreement for both, meaning that scintigraphy is less suitable for assessing left ventricular volumes, and less reliable in assessment of ejection fractions. Echocardiography seems to remain the most widely used and reliable technique for this part of the diagnostic work up.

Quantification of left ventricular volumes and ejection fraction from gated 99mTc-MIBI SPECT: MRI validation of the EXINI heart software package

The aim of the study was to validate the accuracy of the EXINI heart software (EXINI) package in assessing left ventricular end-diastolic/systolic volumes (EDV, ESV) and ejection fraction (LVEF) from gated (99m)Tc-MIBI single-photon emission tomography (SPECT). Cardiac magnetic resonance imaging (cMRI) was used as reference. Furthermore, effects of perfusion defects and image quality in SPECT on correlation between gated SPECT and magnetic resonance imaging were investigated.

METHODS

Seventy patients were examined using gated SPECT (rest study, eight gates per cardiac cycle). EDV, ESV and LVEF were calculated from gated SPECT using EXINI. Directly before or after SPECT, cMRI (20 gates cardiac per cycle) was performed. EDV, ESV and LVEF were calculated using Simpson's rule. Perfusion defects were quantified using the summed-rest-score (SRS). Total number of myocardial counts were used to rate image quality.

RESULTS

Correlation between results of gated SPECT and cMRI was high for EDV (R = 0.89) and ESV (R = 0.94) and good for LVEF (R = 0.78). ESV (EXINI 54 +/- 31 ml versus cMRI 57 +/- 34 ml) and LVEF (EXINI 62.9 +/- 11.7% versus cMRI 60.6 +/- 13.9%) did not differ significantly whereas EXINI overestimated EDV significantly compared with cMRI (EXINI 144 +/- 41 ml versus cMRI 137 +/- 36 ml; P<0.005). No correlation was found between absolute differences of the results given by gated SPECT and cMRI and SRS or total myocardial counts (R < 0.18).

CONCLUSION

End-diastolic volume, ESV and LVEF calculated from gated SPECT using EXINI agree with cMRI over a wide range of values. Correlation between both the methods was good for EDV and ESV, and acceptable for LVEF. No relevant influence of image quality or SRS on the accuracy of EXINI results was found.

EANM/ESC guidelines for radionuclide imaging of cardiac function

Radionuclide imaging of cardiac function represents a number of well-validated techniques for accurate determination of right (RV) and left ventricular (LV) ejection fraction (EF) and LV volumes. These first European guidelines give recommendations for how and when to use first-pass and equilibrium radionuclide ventriculography, gated myocardial perfusion scintigraphy, gated PET, and studies with non-imaging devices for the evaluation of cardiac function. The items covered are presented in 11 sections: clinical indications, radiopharmaceuticals and dosimetry, study acquisition, RV EF, LV EF, LV volumes, LV regional function, LV diastolic function, reports and image display and reference values from the literature of RVEF, LVEF and LV volumes. If specific recommendations given cannot be based on evidence from original, scientific studies, referral is given to "prevailing or general consensus". The guidelines are designed to assist in the practice of referral to, performance, interpretation and reporting of nuclear cardiology studies for the evaluation of cardiac performance.

Quantitation in gated perfusion SPECT imaging: the Cedars-Sinai approach

Cedars-Sinai's approach to the automation of gated perfusion single photon emission computed tomography (SPECT) imaging is based on the identification of key procedural steps (processing, quantitation, reporting), each of which is then implemented, in completely automated fashion, by use of mathematic algorithms and logical rules combined into expert systems. Our current suite of software applications has been designed to be platform- and operating system-independent, and every algorithm is based on the same 3-dimensional sampling scheme for the myocardium. The widespread acceptance of quantitative software by the nuclear cardiology community (QGS alone is used at over 20,000 locations) has provided the opportunity for extensive validation of quantitative measurements of myocardial perfusion and function, in our opinion, helping to make nuclear cardiology the most accurate and reproducible modality available for the assessment of the human heart.

CMR of Ventricular Function

Cardiovascular magnetic resonance (CMR) is the reference standard for the assessment of ventricular dimensions, function, and mass in terms of accuracy and reproducibility. It has been thoroughly validated both ex vivo and against other imaging techniques. Measurements are highly accurate and no geometrical assumptions need to be made about the ventricle. A routine ventricular dataset of images can be acquired in less than 5 minutes and analyzed in about the same time. The field is rapidly advancing with increasing automation and simplification in both image acquisition and analysis. Using parallel and real time imaging techniques, good quality data can be obtained even in patients who are unable to hold their breath. While providing useful information in all patients with suspected heart failure, CMR should particularly be considered in those with poor echo windows, where it can also be combined with myocardial stress. Tagging techniques can provide highly detailed information about myocardial torsion and strain for individual myocardial segments. In a research environment, the very high degree of interscan reproducibility can dramatically reduce the number of patients needed to perform clinical trials.

Quantification of left ventricular volumes and ejection fraction from gated 99mTc-MIBI SPECT: validation of an elastic surface model approach in comparison to cardiac magnetic resonance imaging, 4D-MSPECT and QGS

PURPOSE

The segmentation algorithm ESM based on an elastic surface model was validated for the assessment of left ventricular volumes and ejection fraction from ECG-gated myocardial perfusion SPECT. Additionally, it was compared with the commercially available quantification packages 4D-MSPECT and QGS. Cardiac MRI was used as the reference method.

METHODS

SPECT and MRI were performed on 70 consecutive patients with suspected or proven coronary artery disease. End-diastolic (EDV) and end-systolic (ESV) volumes and left ventricular ejection fraction (LVEF) were derived from SPECT studies by using the segmentation algorithms ESM, 4D-MSPECT and QGS and from cardiac MRI.

RESULTS

ESM-derived values for EDV and ESV correlated well with those from cardiac MRI (correlation coefficients R=0.90 and R=0.95, respectively), as did the measurements for LVEF (R=0.86). Both EDV and ESV were slightly overestimated for larger ventricles but not for smaller ventricles; LVEF was slightly overestimated irrespective of ventricle size. The above correlation coefficients are comparable to those for the 4D-MSPECT and QGS segmentation algorithms. However, results obtained with the three segmentation algorithms are not interchangeable.

CONCLUSION

The ESM algorithm can be used to assess EDV, ESV and LVEF from gated perfusion SPECT images. Overall, the performance was similar to that of 4D-MSPECT and QGS when compared with cardiac MRI. Results obtained with the three tested segmentation methods are not interchangeable, so that the same algorithm should be used for follow-up studies and control subjects.

Differences in left ventricular ejection fraction and volumes measured at rest and poststress by gated sestamibi SPECT

BACKGROUND

Some studies suggested that the poststress left ventricle ejection fraction (LV EF) is lower than rest LV EF in patients with stress-induced ischemia.

METHODS AND RESULTS

By using a 2-day protocol and 30 mCi Tc-99m sestamibi, LV EF, end-systolic volume (ESV), and end-diastolic volume (EDV) were measured with gated SPECT. Of 99 eligible patients, 91 had technically adequate studies. Poststress LV EF minus rest LV EF was defined as DeltaLV EF. DeltaEDV and DeltaESV were similarly defined. Rest and poststress LV EF (r = 0.89), EDV (r = 0.78), and ESV (r = 0.93) were highly correlated (P <.001). Rest LV EF, EDV, and ESV were not significantly different between patients with and without stress-induced ischemia. DeltaLV EF was significantly lower in patients with stress-induced ischemia (-3.5% +/- 4.5% vs -1.1% +/- 4.7%, P = .02). Mean LV EF poststress in ischemic patients was 55.0% +/- 10.5% vs 61.2% +/- 10.0% in nonischemic patients (P = .008). However, only 1 patient (3%) with ischemia had DeltaLV EF that exceeded the 95% confidence limit of DeltaLV EF for normal patients. Ischemia was significantly associated with increased DeltaEDV and DeltaESV (P < .01).

CONCLUSIONS

Stress-induced ischemia is associated with poststress reduction in LV EF and increased poststress EDV and ESV. However, the effect of ischemia on the difference between poststress and rest EF measurements is modest and rarely exceeds the confidence limits in normal patients undergoing 2-day protocols. In most patients, poststress LV EF is an accurate reflection of rest LV EF.

Development of quantification software using model-based segmentation of left ventricular myocardium in gated myocardial SPECT

Gated myocardial single photon emission computed tomography (SPECT) is being used for the diagnosis of coronary artery diseases. In this study, we developed new software for the quantification of volumes and ejection fraction (EF) on the gated myocardial SPECT data using a cylindrical model. Volumes and EF by developed software were validated by comparing with those quantified by quantitative gated SPECT (QGS) software. Cylinder model for left ventricular myocardium was used to eliminate background activity and count profiles across the myocardium were fitted to the Gaussian curve to determine the endocardial and epicardial boundary. End-diastolic volume (EDV), end-systolic volume (ESV) and EF were calculated using this boundary information. Gated myocardial SPECT was performed in 83 patients. EDV, ESV and EF values estimated using present method were compared to those obtained using the commercialized software QGS, and reproducibility in the parameter estimation was assessed. EF, EDV and ESV obtained using two methods were correlated well (correlation coefficients = 0.96, 0.96 and 0.98). The correlation between the parameters repetitively estimated from the same data set by an operator was very high (correlation coefficients = 0.96, 0.99 and 0.99 for EF, EDV and ESV). On the repeated acquisition, reproducibility was also high with correlation coefficients of 0.89, 0.97 and 0.98. The present software will be useful for the development of new parameters for describing the perfusion and function of the LV.

Cardiovascular magnetic resonance in the quantitative assessment of left ventricular mass, volumes and contractile function

Cardiovascular magnetic resonance is a well validated, highly accurate and reproducible technique for the assessment of ventricular volumes, function and mass. State of the art cardiovascular magnetic resonance practice is capable of a ventricular assessment that includes not only systolic but also diastolic function. Thus, it provides an insight into the complex changes in ventricular morphology, physiology and function in cardiovascular disease. This has produced great interest not only in its clinical utilization but also as an important research tool. As refinement of the technique continues to incorporate hardware and software developments, the technique becomes quicker, more accurate and easier to analyse. Here, we review recent developments and current practice.

Incremental prognostic value of combined perfusion and function assessment during myocardial gated SPECT in patients aged 75 years or older

BACKGROUND

Perfusion and functional data obtained during gated single photon emission computed tomography (SPECT) have proven prognostic value in the middle-aged patient population. The aim of this study was to investigate whether perfusion and functional cardiac gated SPECT data have prognostic value in patients aged 75 years or older.

METHODS AND RESULTS

We studied clinical and gated SPECT predictors of cardiac and all-cause death in 294 patients aged 75 years or older with known or suspected coronary artery disease who were referred for tetrofosmin cardiac gated SPECT imaging. Summed perfusion scores were calculated in a 17-segment model by use of commercially available software (4D-MSPECT). Left ventricular functional data were calculated by use of QGS gated SPECT software. The median age of the study population was 78 years (range, 75-91 years). There were 160 men (54%) and 134 women (46%). During a median follow-up of 25.9 months (range, 1.8-36 months), 47 patients (16%) died (27 cardiac deaths). In a multivariate Cox proportional hazards regression analysis, the summed rest score (chi2 gain = 8.0, P = .009), transient ischemic dilatation index (chi2 gain = 6.3, P = .012), and resting left ventricular ejection fraction (chi2 gain = 7.0, P = .030) were independent predictors of all-cause death. The summed rest score (chi2 gain = 8.2, P = .004) and resting end-systolic volume (chi2 gain = 13.7, P = .005) were independent predictors of cardiac death.

CONCLUSIONS

This study showed that gated SPECT left ventricular functional data assessed during myocardial gated SPECT provide independent and incremental information above clinical and perfusion SPECT data for the prediction of cardiac and all-cause death in patients aged 75 years or older referred for myocardial SPECT imaging.

Evaluation of the Quantitative Gated SPECT (QGS) software program in the presence of large perfusion defects

OBJECTIVES

To evaluate the reproducibility and operator dependence for the quantitative regional left ventricular functional parameters (LVFP) assessed by Cedars-Sinai's Quantitative automated gated SPECT (QGS) software.

METHODS

The QGS algorithm was reviewed in detail and potential operator dependencies were defined. Series of prototypes were selected, consisting of (a) normal perfusion, (b) perfusion defects in all perfusion regions, (c) perfusion studies of patients with angiographic confirmed normal coronary arteries, proximal (>or=70% stenoses) single and multiple vessel disease, and (d) spurious activity in close proximity. While defining and re-orienting the volume containing the left ventricle, the operator adjusted 8 variables/degrees of freedom (DF). The software was used without further operator interventions. Results were expressed as a coefficient of variation (COV). Separate COV were calculated per distinct DF. A segment was considered not robust when the COV did exceed 20% in a single DF, 15% in at least 2 DF, or 10% in at least 3 DF.

RESULTS

Regional left ventricular EF and volumes showed excellent reproducibility. Normal perfusion and the vessel disease prototypes showed an excellent COV (for all re-orientation steps [33/prototype]) mostly below 5% for LVFP. However, regional wall motion and thickening became less reliable in the presence of large perfusion defects or artifacts.

CONCLUSIONS

Quantitative estimates for regional left ventricular functional data show excellent reproducibility using automated gated SPECT. However, there may be substantial operator dependency in the presence of large defects or spurious activity in close proximity.

Inter-institution preference-based variability of ejection fraction and volumes using quantitative gated SPECT with 99mTc-tetrofosmin: a multicentre study involving 106 hospitals

PURPOSE

Inter-institution reproducibility of gated SPECT quantification based on institutional preferences was evaluated. This sort of variability is crucial for a multicentre study when many hospitals are involved.

METHODS

A total of 106 institutes participated in this study and were grouped according to their use of five workstation types. Fifteen sets of 99mTc-tetrofosmin gated projection images with normal ejection fraction (EF) (approximately 70%, group A, n = 5), borderline low EF (approximately 50%, group B, n = 5) and low EF with large perfusion defects (approximately 30%, group C, n = 5) were prepared. The projection images were processed by QGS software in each institute based on its own routine settings. Based on 318 QGS results, the reproducibility of EF and volumes was analysed for each group and workstation.

RESULTS

The reproducibility of EF was good in 14 of 15 cases, showing a standard deviation (SD) of <3.6%, and the coefficient of variance of the end-diastolic volume (EDV) was <9.3% in all cases. When the deviation from the average value was analysed, the difference between EF at each institute and the average EF of the workstation (dEF) showed an SD of 2.2-3.7% for each group. The ratio of the EDV divided by the average EDV (rEDV) showed an SD of 0.061-0.069 for each group. One case in group C that had a large anterior defect with low EF showed bimodal EF distribution in one of the five workstations. The SD of EF was workstation dependent, owing to the SPECT reconstruction conditions.

CONCLUSION

The reproducibility in EF and volumes within a workstation was good, even though the gated SPECT preferences varied. This reproducibility study supports the use of gated SPECT as a standard of ventricular function in multicentre studies.

Performance of Thallium-201 Electrocardiography-gated Myocardial Perfusion Single Photon Emission Computed Tomography to Assess Left Ventricular Function

This study evaluated the performance of gated single photon emission computed tomography (SPECT) with thallium-201 (201Tl) in assessing left ventricular ejection fraction (LVEF), end-diastolic volume (EDV), and end-systolic volume (ESV) in Taiwanese by determining repeatability and correlation with two-dimensional (2D) echocardiography. A total of 18 patients underwent two sequential gated SPECT acquisitions within 30 minutes in the resting state to assess repeatability. Another 28 patients who underwent gated SPECT and 2D echocardiography within 7 days were included for comparison. The two sequential measurements were well correlated with respect to LVEF, EDV, and ESV (r = 0.97, 0.95, and 0.97, respectively, all p < 0.0001). Bland-Altman analysis revealed that two standard deviations of the absolute difference between the two sequential measurements for LVEF, EDV, and ESV were 6.4%, 16.8 mL, and 8.6 mL, respectively. For LVEF, EDV, and ESV, correlations between redistribution 201Tl-gated SPECT and echocardiography were also excellent (all r = 0.83, p < 0.0001). LVEF was similar with 201Tl-gated SPECT and echocardiography, but EDV and ESV were significantly higher with echocardiography (p < 0.05). Our study revealed that 201Tl-gated SPECT has high repeatability and excellent correlation with echocardiography for the assessment of LVEF and volumes in Taiwanese. These results support the clinical application of gated SPECT in routine 201Tl myocardial perfusion imaging in Taiwanese.

Clinical usefulness of ECG-gated 18F-FDG PET combined with 99mTC-MIBI gated SPECT for evaluating myocardial viability and function

OBJECTIVES

This study sought to evaluate an imaging approach using gated 99mTc-MIBI (MIBI) SPECT and gated 18F-FDG (FDG) PET for assessment of myocardial viability and cardiac function.

METHODS

Forty-eight patients (38 men, mean age 68.1 +/- 9.6 years) underwent ECG-gated FDG PET and MIBI SPECT within a week. The baseline diagnoses were coronary artery disease (31), mitral regurgitation (1), paroxysmal arrhythmia (10), and dilated cardiomyopathy (6). The gated FDG PET data were analyzed using pFAST software, and the gated MIBI SPECT data were analyzed using QGS software. Fifteen patients were diagnosed with myocardial infarction, and follow-up study was performed to assess the functional outcome four months later. An improvement in LVEF of >5% was defined as significant. The LV myocardium was divided into 17 segments, and regional defect scores were visually assessed using a 4-point scale for each segment (0 = normal, 1 = mildly reduced, 2 = moderately reduced, 3 = absent). A segment with a greater defect score on MIBI SPECT than on FDG PET was defined as a mismatch. The patients were divided into two groups: those with at least two mismatched segments (MM-group), and those with none or one (M-group).

RESULTS

LVEF, EDV and ESV measured by gated FDG PET were highly correlated with those obtained by gated MIBI SPECT (r = 0.848, 0.855 and 0.911, p < 0.0001, respectively). The mean values of LVEF did not differ significantly, but EDV and ESV obtained by gated FDG PET were significantly grater than those obtained by gated MIBI SPECT (p < 0.0001). In 15 patients diagnosed with myocardial infarction, a significant association (p < 0.05) was found between the relative uptake of FDG PET and MIBI SPECT and the functional outcome 4 months later. Global LV function improved in 6 of the 8 patients showing mismatch but in only 1 of the 7 patients with matched defects, resulting in a sensitivity of 86% and specificity of 75%. The overall accuracy to predict global functional outcome was high (80%).

CONCLUSION

This imaging approach allows accurate evaluation of myocardial viability. Furthermore, the high correlations of gated FDG PET and gated MIBI SPECT measurements hold promise for the assessment of left ventricular function using gated FDG PET.

Myocardial Viability: Nuclear Assessment

There are an estimated 5 million patients with congestive heart failure (CHF) in the United States. The long-term outcome in these patients is poor with a 5-year mortality of 70%. There is evidence suggesting that revascularization in patients with viable myocardium can result in reduced event rate in these patients. The presence of viable myocardium best identifies patients who will improve with revascularization. Noninvasive imaging with radionuclide tracers has been used extensively to identify the presence and extent of viable myocardium. We have summarized the role of radionuclide myocardial perfusion and function evaluation in assessment of viable myocardium in this review.

Clinical relevance of left ventricular volumes and function assessed by gated SPECT in paediatric patients

Left ventricular (LV) end-diastolic and end-systolic volumes (EDV, ESV) and ejection fraction (EF) can be measured by echocardiography and gated single photon emission computed tomography (G-SPECT). The literature is rich in works on G-SPECT in adults, but lacks data for children. This work evaluates the accuracy of G-SPECT in children, compared to echocardiography.

PATIENTS AND METHODS

The study comprised 60 children. Eighteen with history of sickle cell disease, 5 dilated cardiomyopathy, 12 valvular heart disease and one with hyperlipidaemia. Other 24 children free from cardiac problems were included. All patients were given 185-370 MBq (5-10 mCi) of 99mTc-MIBI or 99mTc-Myoview. Resting G-SPECT was acquired 45-60 min after injection. LV volumes and EF were measured by G-SPECT and echocardiography.

RESULTS

In all 60 cases, the correlation coefficients between both methods were 0.66 for EDV, 0.73 for ESV and 0.42 for EF. The 36 diseased children yielded fair to weak correlations for EDV, ESV and EF (r = 0.69, 0.74 and 0.41 respectively). The EDV was larger by echocardiography than G-SPECT (81.95 +/- 28.87 vs. 65.91 +/- 31.59 ml, p < 0.01). The ESV was also larger by echocardiography (39.13 +/- 15.96 vs. 23.44 +/- 18.04 ml, p < 0.01). The EF by G-SPECT (67.32 +/- 11.63%) was higher than by echocardiography (52.65 +/- 11.77%), (p < 0.01). The 24 normal subjects yielded almost the same level of weak correlation between both methods for EDV, ESV and EF (r = 0.59, 0.69, and 0.44 respectively).

CONCLUSION

LV volumes and EF computed by G-SPECT correlated poorly with echocardiography in small ventricles. Consequently, G-SPECT has a limited clinical usefulness in paediatrics.

Assessment of ventricular function and mass by cardiac magnetic resonance imaging

Cardiac magnetic resonance imaging is currently the technique of choice for precise measurements of ventricular volumes, function and left ventricular (LV) mass. The technique is 3D and hence independent of geometrical assumptions; this, along with its excellent definition of endocardial and epicardial borders, makes it highly accurate and reproducible. Cardiac magnetic resonance (CMR) is particularly useful in research, as it is highly sensitive to small changes in ejection fraction and mass, and only a small number of subjects are required for a study. The excellent reproducibility makes temporal follow-up of any individual patient in the clinical setting a realistic possibility. This review examines the merits of CMR and describes the techniques used.

Comparison of 16-frame and 8-frame gated SPET imaging for determination of left ventricular volumes and ejection fraction

Electrocardiographic (ECG) gated single-photon emission tomography (SPET) allows for simultaneous assessment of myocardial perfusion and left ventricular (LV) function. Presently 8-frame per cardiac cycle ECG gating of SPET images is standard. The aim of this study was to compare the effect of 8-frame and 16-frame gated SPET on measurements of LV volumes and to evaluate the effects of the presence of myocardial perfusion defects and of radiotracer dose administered on the calculation of LV volumes. A total of 86 patients underwent technetium-99m SPET myocardial perfusion imaging using 16-frame per cardiac cycle acquisition. Eight-frame gated SPET images were generated by summation of contiguous frames. Left ventricular end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were calculated from the 16-frame and 8-frame data sets. The patients were divided into groups according to the administered dose of the radiotracer and the size of the perfusion defect. Results. Sixteen frame per cardiac cycle acquisition resulted in significantly larger EDV (122+/-72 ml vs 115+/-68 ml, P<0.0001), smaller ESV (64+/-58.6 ml vs 67.6+/-59.5 ml, P<0.0001), and higher LVEF (55.3%+/-18% vs 49%+/-17.4%, P<0.0001) as compared to 8-frame SPET imaging. This effect was seen regardless of whether a high or a low dose was administered and whether or not significant perfusion defects were present. This study shows that EDV, ESV and LVEF determined by 16-frame gated SPET are significantly different from those determined by 8-frame gated SPET. The radiotracer dose and perfusion defects do not affect estimation of LV parameters by 16-frame gated SPET.

Measurement of left ventricular volumes and ejection fraction by quantitative gated SPET, contrast ventriculography and magnetic resonance imaging: a meta-analysis

All previous validation studies of quantitative gated single-photon emission tomography (QGS) have examined relatively few patients, and the accuracy of QGS thus remains uncertain. We performed a meta-analysis of data from 301 participants in ten studies that compared QGS using technetium-99m-labelled tracers with contrast left ventriculography (LVG), and from 112 participants in six studies that compared QGS with magnetic resonance imaging (MRI). Linear regression and Bland-Altman analyses were used to evaluate pooled data from individuals across the studies. The correlation between QGS and LVG for end-diastolic volume (EDV) (r=0.81, SEE=27 ml), end-systolic volume (ESV) (r=0.83, SEE=18 ml) and ejection fraction (EF) (r=0.79, SEE=8.3%) was good, as was that between QGS and MRI for EDV (r=0.87, SEE=34 ml), ESV (r=0.89, SEE=27 ml) and EF (r=0.88, SEE=7.2%). However, Bland-Altman plots indicated that LVG minus QGS differences for EDV generated a systematic and random error of 32+/-58 ml (mean+/-2SD), and that MRI minus QGS generated an error of 13+/-73 ml. In the subgroup of patients in whom ECG gating was set at eight intervals, QGS significantly underestimated EF by 7.6%+/-17.4% (mean+/-2SD) compared with LVG and by 6.3%+/-14.6% compared with MRI; no such underestimation was observed in the subgroup in whom ECG gating was set at 16 intervals. We conclude that in patients with ECG gating set at eight intervals, QGS systematically underestimates LV volumes and EF compared with both LVG and MRI. Since QGS also shows considerable variations around the systematic deviations, there remains uncertainty over whether an individual value determined with QGS approximates the true LV volumes and EF.

Left ventricular mass measured by myocardial perfusion gated SPECT. Relation to three-dimensional echocardiography

PURPOSE

The purpose of this investigation was to determine whether left ventricular mass (LVM) assessed from myocardial perfusion gated SPECT (GSPECT) data corresponds with echocardiographic estimates, and whether mass accuracy decreases as relative myocardial wall thickness increases.

MATERIALS AND METHODS

Myocardial perfusion tomograms were selected retrospectively for 37 patients, of whom 18 had Tl-201 and 19 had Tc-99m sestamibi GSPECT poststress data collections, which were subsequently processed using quantitative gated SPECT software (Cedars Sinai Medical Center, Los Angeles, CA). These patients also had clinically indicated echocardiograms for assessment of wall thickness and possible valvular involvement. In addition, LV internal diameter and posterior wall thickness were measured at end-diastole by two-dimensional guided M-mode echocardiography to assess relative myocardial wall thickness, and LVM was measured by three-dimensional echocardiography using an acoustic spatial locator device.

RESULTS

LVM values were not significantly different between GSPECT and three-dimensional echocardiography (153 +/- 39 g versus 146 +/- 35 g, respectively; P = NS). GSPECT correlated significantly (r = 0.63, P < 0.0001) with three-dimensional echocardiography, with a mean difference of 7 +/- 32 g but a substantial root mean squared error of 31 g. Results were similar for similar mass ranges when subgrouped by isotope and by the presence of significant myocardial perfusion defects. Results were independent of relative myocardial wall thickness determined by two-dimensional echocardiography. The two methods yielded similar results in the highest mass range of 400 to 500 g.

CONCLUSIONS

GSPECT and three-dimensional echo LVM correlated significantly, but given the large spread of statistical errors, these two techniques should not be considered interchangeable. Because gamma camera resolution is limited, GSPECT LVM should be viewed as an approximation.

Factors affecting left ventricular ejection fraction using automated quantitative gated SPECT

BACKGROUND

Factors affecting the accuracy of left ventricular ejection fraction (LVEF) quantification using automated quantitative gated SPECT have not been adequately investigated in patients in the clinical setting. Therefore, the authors studied the effect of defect size and Tc-99m tetrofosmin dose on the accuracy of LVEF calculation using the automated QGS program.

MATERIALS AND METHODS

Thirty-two consecutive patients underwent gated rest and stress myocardial perfusion SPECT after administration of 8 and 27 mCi Tc-99m tetrofosmin, respectively. The LVEF was obtained for both the rest and stress studies using the QGS program and compared with the LVEF obtained using quantitative echocardiography performed within 2 weeks. Myocardial perfusion defects were recorded as scarring, ischemia, or mixed scarring and ischemia in 12 left ventricular segments. The defect size was evaluated by adding the number of affected segments.

RESULTS

The mean LVEF calculated using high-dose stress QGS, low-dose rest QGS, and echocardiography was 49.2% +/- 15%, 46.2% +/- 17% and 48.7% +/- 16.9% respectively, with no statistically significant differences. The LVEF obtained using high-dose stress QGS correlated better with echocardiography than did that obtained using low-dose rest QGS (r = 0.86 versus 0.76). In addition, when the high-dose stress LVEF in the 14 patients with normal myocardial perfusion was compared with that in 11 patients who had one- or two-segment perfusion defects, and 7 patients who had perfusion defects in > or = three segments, there was good correlation with echocardiography in the three patient groups (r = 0.85, 0.88, and 0.91, respectively).

CONCLUSIONS

Myocardial perfusion defects do not affect the accuracy of LVEF calculation using automated QGS. High-dose gated myocardial SPECT demonstrated better correlation with quantitative echocardiography LVEF results.

Validation of an evaluation routine for left ventricular volumes, ejection fraction and wall motion from gated cardiac FDG PET: a comparison with cardiac magnetic resonance imaging

The aim of this study was to validate the estimation of left ventricular end-diastolic and end-systolic volumes (EDV, ESV) and ejection fraction (LVEF) as well as wall motion analysis from gated fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in patients with severe coronary artery disease (CAD) using software originally designed for gated single-photon emission tomography (SPET). Thirty patients with severe CAD referred for myocardial viability diagnostics were investigated using a standard FDG PET protocol enhanced with gated acquisition (8 gates per cardiac cycle). EDV, ESV and LVEF were calculated using standard software designed for gated SPET (QGS). Wall motion was analysed using a visual four-point wall motion score on a 17-segment model. As a reference, all patients were also examined within a median of 3 days with cardiovascular cine magnetic resonance imaging (cMRI) (20 gates per cardiac cycle). Furthermore, all gated FDG PET data sets were reoriented in a second run with deliberately misaligned axes to test the quantification procedure for robustness. Correlation between the results of gated FDG PET and cMRI was very high for EDV and ESV ( R=0.96 and R=0.97) and for LVEF ( R=0.95). With gated FDG PET, there was a non-significant tendency to underestimate EDV (174+/-61 ml vs 179+/-59 ml, P=0.21) and to overestimate ESV (124+/-58 ml vs 122+/-60 ml, P=0.65), resulting in underestimated LVEF values (31.5%+/-9.4% vs 34.2%+/-12.4%, P<0.003). The results of reorientations 1 and 2 showed very high correlations (for all R>/=0.99). Segmental wall motion analysis revealed good agreement between gated FDG PET data and cMRI (kappa =0.62+/-0.03). In conclusion, despite small systematic differences which contributed mainly to the lower temporal resolution of gated FDG PET, agreement between gated FDG PET and cMRI was good across a wide range of volumes and LVEF values as well as for wall motion analysis. Therefore, gated FDG PET provides clinically relevant information on function and volumes, using the commercially available software package QGS.

Rapid freehand scanning three-dimensional echocardiography: accurate measurement of left ventricular volumes and ejection fraction compared with quantitative gated scintigraphy

This study was performed to assess clinical feasibility of rapid freehand scanning 3-dimensional echocardiography (3DE) for measuring left ventricular (LV) end-diastolic and -systolic volumes and ejection fraction using quantitative gated myocardial perfusion single photon emission computed tomography as the reference standard. We performed transthoracic 2-dimensional echocardiography and magnetic freehand 3DE using a harmonic imaging system in 15 patients. Data sets (3DE) were collected by slowly tilting the probe (fan-like scanning) in the apical position. The 3DE data were recorded in 10 to 20 seconds, and the analysis was performed within 2 minutes after transferring the raw digital ultrasound data from the scanner. For LV end-diastolic and -systolic volume measurements, there was a high correlation and good agreement (LV end-diastolic volume, r = 0.94, P <.0001, standard error of the estimates = 21.6 mL, bias = 6.7 mL; LV end-systolic volume, r = 0.96, P <.0001, standard error of the estimates = 14.8 mL, bias = 3.9 mL) between gated single photon emission computed tomography and 3DE. There was an overall underestimation of volumes with greater limits of agreement by 2-dimensional echocardiography. For LV ejection fraction, regression and agreement analysis also demonstrated high precision and accuracy (y = 0.82x + 5.1, r = 0.93, P <.001, standard error of the estimates = 7.6%, bias = 4.0%) by 3DE compared with 2-dimensional echocardiography. Rapid 3DE using a magnetic-field system provides precise and accurate measurements of LV volumes and ejection fraction in human beings

Can the estimation of ejection fraction during gated single photon emission computed tomography at rest add information to the cardiac perfusion study?

Left ventricular function is an important prognostic indicator in patients with coronary artery disease. The electrocardiogram gated, myocardial, single photon emission tomography (SPECT) program is coming into wide use. This program permits measurement of end diastolic volume, end systolic volume, and ejection fraction. This study was designed to show whether the measurement of ejection fraction by using (99c)Tc tetrofosmin gated SPECT at rest could give additional information to the interpretation of perfusion. Exercise 99mTc tetrofosmin SPECT and gated (99c)Tc tetrofosmin SPECT at rest were performed in 33 patients with or suspected of having coronary artery disease. Left ventricular ejection fraction was calculated from reconstructed gated SPECT at rest with a software quantitative gated SPECT. The results showed a poor correlation between segmental ejection fraction and segmental perfusion in stress and rest. There was an increasing probability of reversibility as the ejection fraction increased, while there was a greater chance of a fixed defect as the ejection fraction decreased. It is concluded that gated SPECT using (99c)Tc tetrofosmin provides clinically satisfactory functional data that, in combination with the perfusion information, will improve diagnostic and prognostic accuracy without an increase in cost or radiation dose to patients.