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

Low-dose dobutamine stress gated blood pool SPECT assessment of left ventricular contractile reserve in ischemic cardiomyopathy: a feasibility study

PURPOSE

The purpose of the present study was to evaluate the feasibility of gated blood pool single-photon emission computed tomography (GBPS) with low-dose dobutamine (LDD) stress test, performed on a single-photon emission computed tomography (SPECT) camera equipped with cadmium-zinc-telluride (CZT) solid-state detectors, in assessing of left ventricle (LV) contractile reserve in patients with ischemic cardiomyopathy (ICM).

METHODS

A total of 52 patients (age 59 ± 7.2 years, 47 men and 5 women) with ICM and a control group of 10 patients without obstructive coronary artery lesion underwent GBPS and transthoracic echocardiography (TTE) at rest and during LDD stress test (5, 10, 15 µg/kg/min). The duration of each GBPS step was 5 min. Stress-induced changes in LV ejection fraction (ΔLVEF), peak ejection rate, LV volumes, and mechanical dyssynchrony (phase histogram standard deviation, phase histogram bandwidth and entropy) obtained with GBPS were estimated.

RESULTS

All GBPS indices except end-diastolic volume showed significant dynamics during stress test in both groups. The majority of parameters in ICM patients showed significant changes at a dobutamine dose of 10 µg/kg/min as compared to the rest study. Seventeen percent of ICM patients, but none from the control group, showed a decrease in LVEF during stress, accompanied by a significant increase in entropy. The intra- and inter-observer reproducibility was excellent for both rest and stress studies. There was a moderate correlation (r = 0.5, p = 0.01) between GBPS and TTE, with a mean difference value of - 1.7 (95% confidence interval - 9.8; 6.4; p = 0.06) in ΔLVEF.

CONCLUSION

Low-dose dobutamine stress GBPS performed with high-efficiency CZT-SPECT cameras can be performed for evaluating stress-induced changes in LV contractility and dyssynchrony with lower acquisition time. A dobutamine dose of 10 µg/kg/min can potentially suffice to detect stress-induced changes in patients with ICM during GBPS.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04508608 (August 7, 2020).

Development of a new Python-based cardiac phantom for myocardial SPECT imaging

PURPOSE

The aim of this work was to develop a digital dynamic cardiac phantom able to mimic gated myocardial perfusion single photon emission computed tomography (SPECT) images.

METHODS

A software code package was written to construct a cardiac digital phantom based on mathematical ellipsoidal model utilizing powerful numerical and mathematic libraries of python programing language. An ellipsoidal mathematical model was adopted to create the left ventricle geometrical volume including myocardial boundaries, left ventricular cavity, with incorporation of myocardial wall thickening and motion. Realistic myocardial count density from true patient studies was used to simulate statistical intensity variation during myocardial contraction. A combination of different levels of defect extent and severity were precisely modeled taking into consideration defect size variation during cardiac contraction. Wall thickening was also modeled taking into account the effect of partial volume.

RESULTS

It has been successful to build a python-based software code that is able to model gated myocardial perfusion SPECT images with variable left ventricular volumes and ejection fraction. The recent flexibility of python programming enabled us to manipulate the shape and control the functional parameters in addition to creating variable sized-defects, extents and severities in different locations. Furthermore, the phantom code also provides different levels of image filtration mimicking those filters used in image reconstruction and their influence on image quality. Defect extent and severity were found to impact functional parameter estimation in consistence to clinical examinations.

CONCLUSION

A python-based gated myocardial perfusion SPECT phantom has been successfully developed. The phantom proved to be reliable to assess cardiac software analysis tools in terms of perfusion and functional parameters. The software code is under further development and refinement so that more functionalities and features can be added.

The impact of frame numbers on cardiac ECG-gated SPECT images with interpolated extra frames using echocardiography

Background: Cardiac echocardiography and cardiac ECG-gated single-photon emission computed tomography (SPECT) are the most common modalities for left ventricle (LV) volumes and function assessment. The temporal resolution of SPECT images is limited and an ECG provides better temporal resolution. This study investigates the impact of frame numbers on images in terms of qualitative and quantitative assessments.

Methods: In this study, 5 patients underwent echocardiography and cardiac ECG-gated SPECT imaging, and 5 standard views of the LV were recorded to determine LV walls boundaries and volumes. Also, 2 original images with 8 frames and 16 frames per cardiac cycle were recorded simultaneously in a single gantry orbit. Using the data extracted from the LV model, 8 extra new frames were created with interpolation between existing frames of the original 8-frame image. Three series of images (8 and 16 original and 16 interpolated) were reconstructed separately. LV volumes and ejection fraction (EF) were calculated using Quantitative Gated SPECT (QGS) software.

Results: Compared to the original 8-frame gating, original 16-frame gated images resulted in larger end-diastole volume (EDV) (mean ± SD: 68.6 ± 27.11 mL vs 66.2±25.41 mL, p<0.001), smaller end-systole volume (ESV) (mean ± SD: 24.6±8.7 mL vs 26±7.3 mL, p<0.001), and higher EF (64% vs 60.2%, p<0.001). The results for the interpolated series were also different from the original images (closer to the original 16-frame series rather than 8-frame).

Conclusion: Changing the frame number from 8 to 16 in cardiac ECG-gated SPECT images caused a significant change in LV volumes and EF. Frame interpolation with sophisticated algorithms can be used to improve the temporal resolution of SPECT images.

Assessment of Left Ventricular Ejection Fraction by Thallium-201 Myocardial SPECT-CT in Patients with Angina Pectoris: Comparison with 2D Echocardiography

Purpose

Left ventricular (LV) ejection fraction (EF) is an important parameter for assessing cardiac systolic function and predicting prognosis in patients with cardiovascular disease. The aim of this study was to evaluate the feasibility of assessing LVEF by Tl-201 hybrid myocardial single-photon emission computed tomography (SPECT)/CT using two attenuation correction methods in patients with angina pectoris.

Methods

A total of 339 patients with angina pectoris (62.8 ± 12.9 years, male:female = 206:133) were analyzed. All patients underwent Tl-201 myocardial SPECT/CT and transthoracic two-dimensional (2D) echocardiograph. We compared LVEF assessed by SPECT/CT using two attenuation correction methods: CT-based attenuation correction (CTAC) and non-attenuation correction (non-AC) methods and 2D echocardiography.

Results

LVEF assessed by either of the two attenuation correction techniques and 2D echocardiography showed moderate correlation in all patients with angina pectoris (r = 0.487 for CTAC and r = 0.473 for non-AC, p < 0.001). Results were similar in the subgroup of patients with perfusion abnormalities on myocardial SPECT/CT images. Overall diagnostic performances were similar for the CTAC and non-AC methods for evaluating normal and decreased LVEF by myocardial SPECT/CT.

Conclusion

LVEF measured by the CTAC method of Tl-201-gated myocardial SPECT/CT was comparable with the conventional non-AC method in patients with angina pectoris and in the subgroup of patients with perfusion abnormality. Tl-201-gated myocardial hybrid SPECT/CT can be a reliable tool in the assessment of LVEF in clinic.

The prognostic value of non-perfusion variables obtained during vasodilator stress myocardial perfusion imaging

Myocardial perfusion imaging (MPI) is an established diagnostic test that provides useful prognostic data in patients with known or suspected coronary artery disease. In more than half of the patients referred for stress testing, vasodilator stress is used in lieu of exercise. Unlike exercise, vasodilator stress does not provide information on exercise and functional capacity, heart rate recovery, and chronotropy, and ECG changes are less frequent. These non-perfusion data provide important prognostic and patient management information. Further, event rates in patients undergoing vasodilator MPI are higher than in those undergoing exercise MPI and even in those with normal images probably due to higher pretest risk. However, there are a number of non-perfusion variables that are obtained during vasodilator stress testing, which have prognostic relevance but their use has not been well emphasized. The purpose of this review is to summarize the prognostic values of these non-perfusion data obtained during vasodilator MPI.

Automated Quantitative Nuclear Cardiology Methods

Quantitative analysis of SPECT and PET has become a major part of nuclear cardiology practice. Current software tools can automatically segment the left ventricle, quantify function, establish myocardial perfusion maps, and estimate global and local measures of stress/rest perfusion, all with minimal user input. State-of-the-art automated techniques have been shown to offer high diagnostic accuracy for detecting coronary artery disease, as well as predict prognostic outcomes. This article briefly reviews these techniques, highlights several challenges, and discusses the latest developments.

The impacts of severe perfusion defects, akinetic/dyskinetic segments, and viable myocardium on the accuracy of volumes and LVEF measured by gated ⁹⁹mTc-MIBI SPECT and gated ¹⁸F-FDG PET in patients with left ventricular aneurysm: cardiac magnetic resonance imaging as the reference

BACKGROUND

To compare the accuracy of end-diastolic and end-systolic volumes (EDV, ESV) and LV ejection fraction (LVEF) measured by both GSPECT and GPET, using cardiac magnetic resonance imaging (CMR) as a reference. Furthermore, the impacts of severe perfusion defects, akinetic/dyskinetic segments, and residual viable myocardium on the accuracy of LV functional parameters were investigated.

METHODS

Ninety-six consecutive patients with LV aneurysm and LV dysfunction (LVEF 32 ± 9%) diagnosed by CMR were studied with GSPECT and GPET. EDV, ESV, and LVEF were calculated using QGS software.

RESULTS

Correlations of volumes were excellent (r 0.81-0.86) and correlation of LVEF was moderate (r 0.65-0.76) between GSPECT vs CMR and between GPET vs CMR. Compared with CMR, ESV was overestimated by GSPECT (P < .01) and underestimated by GPET (P < .0001); EDV was underestimated by GPET (P < .001); LVEF was underestimated by GSPECT but overestimated by GPET (both P < .001). Multivariate regression analysis revealed that the number of segments with severe perfusion defects (P < .001) was the only independent factor which was correlated to the EDV difference between GSPECT and CMR, the number of akinetic/dyskinetic segments with absent wall thickening (WT) was the only independent factor which was significantly correlated to the differences of ESV and LVEF measurements between GSPECT vs CMR and between GPET vs CMR (P < .0001), respectively. Neither the mismatch score nor the segments with viable myocardium were correlated to the differences of LV volumes and LVEF measurements between different imaging modalities.

CONCLUSIONS

In LV aneurysm patients, LV volumes and LVEF measured by both GSPECT and GPET imaging correlated well with those determined by CMR, but should not be interchangeable in individual patients. The accuracy of LVEF measured by GSPECT and GPET was affected by the akinetic/dyskinetic segments with absent WT.

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 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.

Evaluation of baseline contractile reserve vs dyssynchrony as a predictor of functional improvement and long term outcome after resynchronization pacing therapy: a radionuclide stress study

AIM

To assess the predictive value of baseline ventricular dyssynchrony and myocardial contractile reserve (mCR) in identifying responders to cardiac resynchronization therapy (CRT).

METHODS

We prospectively studied 57 patients selected for CRT according to current recommendations. Regional dyssynchrony was evaluated by parametric phase imaging of ecg-gated equilibrium radionuclide angiography (ERNA). The mean inter-ventricular phase delay and the standard deviation to mean left ventricular (LV) phase angle were used as a measure of inter- and intra-ventricular dyssynchrony, respectively. Change in LV ejection fraction (LVEF) during low-dose dobutamine (LDD) was measured to assess mCR. ERNA was repeated at 6 months to evaluate changes in LVEF after CRT. Combined end-points of re-hospitalization for heart failure, heart transplantation, and cardiac death were assessed over a period of 76 months (mean 43 ± 31).

RESULTS

Baseline dyssynchrony was present in most patients (85%). After CRT only one half of patients showed a reduction in intra-ventricular dyssynchrony and 33% an increase in LVEF by >5%. Improvement of LVEF was not predicted by baseline LVEF, clinical presentation, dyssynchrony parameters or QRS duration. There was a significant relationship between changes in LVEF during LDD testing and after CRT (r = 0.65; P < .0001). Logistic regression analysis identified mCR as independent predictor of improvement in LVEF (P = .039; OR = 3.84; CI 95% = 1.06-13.9), resynchronization (P = .046; OR = 4.20; CI 95% = 1.03-17.2), and event-free survival (P = .002; OR = 0.10; CI 95% = 0.02-0.43).

CONCLUSIONS

In patients with left ventricular dysfunction and baseline dyssynchrony as assessed by ERNA, evaluation of mCR during LDD may help predicting functional improvement and selecting potential responders to CRT.

The relationship between aminoterminal propeptide of type III procollagen and heart rate variability parameters in heart failure patients: a potential serum marker to evaluate cardiac autonomic control and sudden cardiac death

BACKGROUND

Cardiac extra-cellular matrix (ECM) fibrosis plays an important role in the pathophysiology of heart failure (HF). It may provide electrical heterogeneity and a substrate for arrhythmogenicity, which may cause sudden cardiac death (SCD).

METHODS

Twenty-one patients with manifestations of HF and a left ventricular ejection fraction (LVEF) ≤50% were enrolled. The median age was 62 years and median LVEF was 33%. Time- and frequency-domain analysis of heart rate variability (HRV) on 24 h ambulatory electrocardiography recording was assessed. Serum markers of ECM turnover including type I and III aminoterminal propeptide of procollagen (PINP and PIIINP), matrix metalloproteinase-2 and -9 (MMP-2 and MMP-9), and tissue inhibitor of metalloproteinase-1 (TIMP-1) were analyzed.

RESULTS

The serum PIIINP concentration was correlated significantly with standard deviation of all normal to normal R-R intervals (SDNN) (r=-0.722, p=<0.001), percentage of adjacent NN interval differences >50 ms (pNN50) (r=-0.528, p=0.014), percentage of adjacent NN interval differences >20 ms (pNN20) (r=-0.545, p=0.002), very low frequency (VLF) (r=-0.490, p=0.024), low frequency (LF) (r=-0.491, p=0.024), and high frequency (HF) (r=-0.513, p=0.018). PINP, MMP-2, -9, TIMP-1 were not correlated with time- and frequency-domain analysis of HRV.

CONCLUSIONS

PIIINP was significantly correlated with time- and frequency-domain analysis of HRV in HF patients. PIIINP is a potential serological marker to evaluate cardiac autonomic control and risk of SCD in HF patients.

Influence of extracardiac activity and perfusion abnormalities on myocardial perfusion gated SPECT parameters: interobserver analysis

OBJECTIVE

Extracardiac activity (ECA) may affect interpretation of gated SPECT myocardial perfusion studies (MPSs). To solve this problem, available softwares include myocardial edge delimitation.

PURPOSE

To evaluate the influence of ECA in automatic myocardial edge detection under normal conditions and with abnormal perfusion and also evaluate the reproducibility of semi-automatic processing.

METHODS

A total of 100 MPSs, 50 with ECA, were analyzed. Each subgroup included 25 cases with perfusion abnormalities. The cases were processed automatically and by 4 independent operators with different levels of experience. Commercial QGS and QPS softwares were used with tools to mask and relocate the left ventricle area. Functional parameters (final diastolic and systolic volumes and ejection fraction) and perfusion parameters such as the reversibility perfusion score and rest perfusion defect extension were analyzed. The data were compared with Pearson's correlation and Student's test.

RESULTS

Interobserver correlation significantly worsened with the presence of ECA and was moderately affected by perfusion abnormalities. More experienced observers presented better correlation. Reproducibility was greater for the functional perfusion parameters, independently of the observer's experience.

CONCLUSIONS

ECA significantly affects automatic edging delimitation, affecting the MPS values. Interobserver reproducibility with manual processing was more altered regarding functional parameters than in the perfusion scores. Perfusion abnormalities did not interfere with software reproducibility, and when present, better correlation was found. If ECA is not present, manual intervention should be avoided.

The effects of technological developments on nuclear medicine technologist productivity: a systematic review

OBJECTIVES

Nuclear medicine has changed rapidly as a result of technological developments. Very little is reported on the effects these developments may have on technologist productivity. This study aims to determine whether advances have created a workplace where more patient studies can be performed with fewer technologists. The level of change in automation or time taken to perform a routine task by the nuclear medicine technologist as a result of technological development over the past decade is reported.

METHODS

A systematic review was conducted using Embase.com, Medline, INSPEC, and Cinahl. Two authors reviewed each article for eligibility. Technological developments in routine areas over the past decade were reviewed. The resultant automation or time effects on data acquisition, data processing, and image processing were summarized.

RESULTS

Sixteen articles were included in the areas of myocardial perfusion, information technology, and positron emission tomography (PET). Gamma camera design has halved the acquisition time for myocardial perfusion studies, automated analysis requires little manual intervention and information technologies and filmless departments are more efficient. Developments in PET have reduced acquisition to almost one-fifth of the time.

CONCLUSIONS

Substantial efficiencies have occurred over the decade thereby increasing productivity, but whether staffing levels are appropriate for safe, high quality practice is unclear. Future staffing adequacy is of concern given the anticipated increasing service needs.

Comparison of gated SPECT, echocardiography and cardiac magnetic resonance imaging for the assessment of left ventricular ejection fraction and volumes

BACKGROUND

Left ventricular ejection fraction (LVEF), end-diastolic volume (EDV) and end-systolic volume (ESV) can be determined non-invasively by two-dimensional enchocardiography (ECHO), gated sinle photon emission computed tomography (GSPECT) and cardiac magnetic resonance imaging (CMRI). This study was designed to analyze the concordance between LVEF, EDV and ESV values derived from ECHO, GSPECT and CMRI.

METHODS

ECHO, GSPECT and CMRI were performed in a group of 21 patients with suspected coronary artery disease. LVEF, EDV and ESV values were calculated.

RESULTS

The mean LVEF measured with GSPECT, ECHO and CMRI were 55.9+/-17.8%, 55.7+/-16.4% and 56.4+/-15.7%, respectively. The mean EDV measured with GSPECT, ECHO and CMRI were 109.2+/-42.45 mL, 127.5+/-42.2 mL, 91.1+/-38.0 mL, respectively. The mean ESV measured with GSPECT, ECHO and CMRI were 54.2+/-41.2 mL, 59.9+/-37.6 mL and 41.8+/-26.9 mL, respectively. The results of linear regression analysis showed very good correlation between LVEF and ESV values derived from GSPECT, ECHO adn CMRI (r=0.91, r=0.92, r=0.97 for LVEF and r=0.86, r=0-91, r=0.91 for ESV, P<0.01). Good correlations were found between EDV values obtained from GSPECT, ECHO and CMRI (r=0.71, r=0.68, r=0.73, P<0.01). Agreement between these techniques in LVEF values was also good, but not in LV volumes, according to Bland-Altman plots.

CONCLUSIONS

This study showed good overall correlations between LVEF, EDV and ESV values derived from GSPECT, ECHO and CMRI. LVEF obtained from any of these three imaging modalities could be used interchangeably. However, care should be taken in comparing LV volumes.

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.

Comparison of radionuclide ventriculography using SPECT and planar techniques in different cardiac conditions

PURPOSE

Accurate assessment of ventricular function is required to optimize therapeutic management of cardiac diseases. The aim of this study was to correlate planar equilibrium multigated acquisition (MUGA) with tomographic ventriculography (SPECT) in patients with diverse volumes and wall motion abnormalities.

METHODS

Eighty-three studies in 80 patients (56+/-14 years; 56% women) were classified according to ventricular dilation, wall motion abnormalities and systolic dysfunction. Left and right ventricular ejection fraction (LVEF and RVEF) and end-diastolic and end-systolic left ventricular volumes (EDV and ESV) were obtained using a commercial QBS program for SPECT. On planar acquisition, LVEF and RVEF were obtained using standard techniques and volumes were determined using the count-based method, without blood sampling.

RESULTS

A. Total group: With the planar method, LVEF was 44+/-17%, RVEF 42+/-13%, left EDV 147+/-97 ml (range 31-487 ml) and left ESV 93+/-85 ml (range 15-423 ml); with SPECT the corresponding values were 40+/-20%, 49+/-16%,131+/-95 ml and 91+/-89 ml, respectively (p=NS for all but RVEF). Linear correlation was 0.845 for LVEF, 0.688 for RVEF, 0.927 for left EDV and 0.94 for left ESV, with good intra-class correlation. B. Subgroups: Global and intra-class correlations between planar imaging and SPECT were high for volumes, RVEF and LVEF in all subgroups, except in patients with normal wall motion and function, who showed smaller volumes with SPECT. The group with diffuse wall motion abnormalities had a lower EDV on SPECT. In the abnormal left ventricle, RVEF was higher with SPECT.

CONCLUSION

Good correlation and agreement exist between SPECT and planar MUGA with respect to LVEF and left ventricular volumes. SPECT is useful in patients with functional abnormalities, but less reliable in those with normal small cavities. A combined technique is still necessary, and RVEF should be interpreted cautiously.

The expanding role of left ventricular functional assessment using gated myocardial perfusion SPECT: the supporting actor is stealing the scene

BACKGROUND

Gating of single-photon emission computed tomography (SPECT) has significantly improved the reliability and diagnostic accuracy of myocardial perfusion imaging. The functional parameters derived from this technique, mainly left ventricular volumes and ejection fraction, have been demonstrated to be accurate and reproducible. They are able to increase the detection of severe and extensive coronary artery disease and show a significant incremental prognostic power over perfusion abnormalities. Therefore, the importance given to gated SPECT functional data has progressively grown.

DISCUSSION

This circumstance has further expanded the indications for myocardial perfusion imaging and strengthened its position among the different imaging modalities. Moreover, several studies show that the evaluation of ventricular function may have a leading part in justifying the execution of perfusion scintigraphy in various clinical conditions.

AIM

Aim of this review is to describe this evolution of gated SPECT functional assessment from a supporting rank with respect to perfusion, to a main actor position in the field of cardiac imaging.

Myocardial perfusion defects with near-to-absent count reduction: a comparison of gated SPECT to radionuclide ventriculography in the determination of left ventricular function

OBJECTIVE

The main aim of the study was, to estimate the impact of perfusion defects including significantly depleted areas of varying size on gated perfusion SPECT (GPS) determined ejection fraction (EF) measurements in comparison to radionuclide ventriculography (RVG). A secondary objective was the evaluation of the GPS-RVG agreement of EF in patients with normal and deteriorated left ventricular function, separately.

METHODS

Fifty-nine patients having perfusion defects including at least one segment with no visible tracer uptake in rest myocardial GPS related to myocardial infarction (older than 15 days) were studied. Myocardial perfusion was visually analyzed using a 17 segment-model, on a five-point (0-4) grading system in which Grade-4 (0-9% maximal uptake) represents cold defects. The patients with >or=4 adjacent, with 2-3 adjacent and with 1 single cold segments were named as Group1(GR1), Group2(GR2) and Group3(GR3), respectively. Secondly, the patients were re-grouped according to RVG-EF values. (Group A: patients with EF<50%; Group B: patients with EF>or=50%). In each group, the GPS-EFs were compared with RVG performed within one week and also the variations of GPS-RVG EF differences among the groups were statistically analyzed.

RESULTS

In overall (r=0.86) and in each subgroup, EFs obtained by GPS were well correlated with RVG. However, in overall (difference mean EF% [dEF%]=4.6+/-6.7, p<0.001) as well as in subgroup evaluation, GPS significantly (p<0.005) underestimated EF. There was no statistically significant difference in GPS-RVG EF variations between GR1, GR2 and GR3 (p>0.05). The RVG-mean differences and RVG-correlation coefficients calculated for GR1,GR2 and GR3 were dEF%=3.1+/-4.6, r=0.85; dEF%=3.7+/-6.03, r=0.80 and dEF%=6.2+/-8.03, r=0.79, respectively. Mean dEF% was statistically higher in group-B than group-A (mean difference of dEF%=4,2, p<0.05). In group-A, GPS-EF values were better agreed with RVG (dEF%=3.34, r=0.75) than in group-B (dEF%=7.52, r=0.53).

CONCLUSION

The stability of the calculation algorithm of QGS in EF calculation of patients with large depleted infarct areas could be confirmed. The agreement of GPS determined EF is higher in patients having myocardial integrity loss and left ventricular dysfunction.

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.

Evaluation of left ventricular volumes and ejection fraction by automated gated myocardial SPECT versus cardiovascular magnetic resonance

BACKGROUND

Electrocardiogram-gated myocardial single-photon emission computed tomography (SPECT) with (99m)Tc-tetrofosmin allows simultaneous evaluation of myocardial perfusion and function. In this study, left ventricular volumes, ejection fraction (LVEF), and left ventricular wall volume (LVWV) derived from gated SPECT were compared with measurements from cardiovascular magnetic resonance (CMR), performed within a few hours.

METHODS

The study population included 55 patients with known or suspected coronary artery disease, including 13 patients with recent acute myocardial infarction. End-diastolic (EDV) and end-systolic (ESV) volumes, LVEF and LVWV were derived automatically from gated SPECT using commercially available software (QGS). In the CMR studies, manually delineated endocardial and epicardial borders on short-axis slices were used to calculate the volumes.

RESULTS

Gated SPECT underestimated EDV by 35 +/- 14 ml (mean +/- SD) (P < 0.001), ESV by 10 +/- 13 ml (P < 0.001), and LVEF by 4 +/- 7 percentage points (P < 0.001). There were no systematic difference in EDV, ESV or LVEF between the methods. SPECT underestimated LVWV by 49 +/- 30 ml (P < 0.001), with a trend towards increasing underestimation by SPECT for larger wall volumes.

CONCLUSION

These findings show that gated SPECT slightly underestimates EDV, ESV and LVEF compared with CMR. This underestimation is systematic, however, indicating that ventricular volumes derived from gated SPECT are robust enough to guide clinical management. Estimates of LVWV in patients with large wall volumes are less accurate.

Assessment of left ventricular function and volumes for patients with dilated cardiomyopathy using gated myocardial perfusion SPECT and comparison with echocardiography

AIM

Left ventricular function, volumes and regional wall motion provide valuable diagnostic information and are of long-term prognostic importance in patients with dilated cardiomyopathy (DCM). This study was designed to compare the effectiveness of two-dimensional echocardiography and gated single photon emission computed tomography (SPECT) to evaluate these parameters in patients with DCM.

METHODS

Gated SPECT and two-dimensional echocardiography were performed in 45 patients with DCM, and in 10 normal subjects as the control group. Patients were divided into two groups according to the aetiology of DCM: group I, ischaemic DCM (n=30); group II, non-ischaemic DCM (n=15). All patients and the control group underwent resting myocardial gated SPECT, 45 min after injection of 555 MBq of Tc-methoxyisobutyl-isonitrile (Tc-MIBI). Gated SPECT data, including left ventricular volumes and left ventricular ejection fraction (LVEF), were processed using an automated algorithm. Simpson's method was used to evaluate these parameters. Regional wall motion was evaluated using both modalities and scored using a 16-segment model with a five-point scoring system. Perfusion defects were expressed as a percentage of the whole myocardium planimetered by a bull's-eye polar map of composite non-gated SPECT. Myocardial perfusion was scored using a 16-segment model with a four-point scoring system.

RESULTS

Mean perfusion defects and perfusion defect scores were 25+/-13% and 1.12+/-0.36 in group I and 4+/-8% and 0.76+/-0.26 in group II (P<0.01). The overall agreement between the two imaging modalities for the assessment of regional wall motion was 57% (403/720 segments: 269/480 segments in group I and 134/240 segments in group II). With gated SPECT, LVEF was 27+/-9%, the end-diastolic volume (EDV) was 212+/-71 ml and the end-systolic volume (ESV) was 160+/-67 ml. With echocardiography, these values were 29+/-8%, 197+/-56 ml and 139+/-47 ml, respectively. The correlation between gated SPECT and two-dimensional echocardiography was good (r=0.72, P<0.01) for the assessment of LVEF. The correlation was also good for EDV and ESV, but with wider limits of agreement (r= 0.71, P<0.01 and r=0.71, P<0.01, respectively) and with significantly higher values with gated SPECT (P<0.01). For patients with a perfusion defect of <20% or low myocardial perfusion scores, a higher correlation was found between the two methods for the assessment of LVEF, EDV and ESV. On the other hand, the correlation was lower for the assessment of wall motion.

CONCLUSIONS

Gated SPECT and two-dimensional echocardiography correlate well for the assessment of left ventricular function and volumes. Gated SPECT has the advantage of providing information about left ventricular function, dimensions and perfusion.

Left ventricular function parameters obtained from gated myocardial perfusion SPECT imaging: a comparison of two data processing systems

BACKGROUND AND AIM

The Cedars-Sinai Quantitative Gated Single Photon Emission Computed Tomography (SPECT) (QGS) program, used to quantify left ventricular function parameters from gated myocardial perfusion scintigraphy (MPS), has been extensively validated and compared with other methods of quantification. However, little is known about the reproducibility of QGS on different processing systems. This study compared the findings of QGS running on workstations provided by two different manufacturers.

METHODS

Gated rest MPS studies of 50 patients were analysed retrospectively. Filtered back-projection (FBP) was performed using identical parameters on Philips Pegasys and Nuclear Diagnostics Hermes workstations to produce gated short-axis (SA) slices. In addition, the gated SA slices reconstructed on the Pegasys were transferred to the Hermes. QGS was used to calculate the end-diastolic volume (EDV), end-systolic volume (ESV) and left ventricular ejection fraction (LVEF) in each case.

RESULTS

The mean+/-standard deviation differences between the Pegasys and Hermes function parameters were -7.06+/-3.91 ml (EDV), -5.54+/-3.21 ml (ESV) and +1.14%+/-1.43% (LVEF) when data were reconstructed on different systems, and -0.16+/-1.58 ml (EDV), -0.10+/-1.02 ml (ESV) and +0.14%+/-0.73% (LVEF) when data were reconstructed on the same system. Bland-Altman plots showed definite trends for EDV and ESV for data reconstructed on different systems, but no trends were seen for data reconstructed on the same system.

CONCLUSIONS

When data were reconstructed on two separate systems, the difference between the function parameters obtained from Pegasys and Hermes could be ascribed to differences in the reconstruction process on each system despite the use of identical parameters (filters, etc). However, when the same reconstructed data were analysed on both systems, no significant difference in left ventricular function parameters was observed.

Evaluation of left ventricular function and volume in patients with dilated cardiomyopathy: gated myocardial single-photon emission tomography (SPECT) versus echocardiography

BACKGROUND

Left ventricular function, volumes and regional wall motion provide valuable diagnostic information and are of long-term prognostic importance in patients with dilated cardiomyopathy (DCM). This study was designed to compare the effectiveness of 2D-echocardiography and gated single-photon emission tomography (SPECT) for evaluation of these parameters in patients with DCM.

PATIENTS AND METHODS

Gated SPECT and 2D-echocardiography were performed in 33 patients having DCM. Gated SPECT data, including left ventricular volumes and left ventricular ejection fraction (LVEF), were processed using an automated algorithm. Standard technique was used for 2D-echocardiography. Regional wall motion was evaluated using both modalities and was scored by two independent observers using a 16-segment model with a 5-point scoring system.

RESULTS

The overall agreement between the two imaging modalities for the assessment of regional wall motion was 56% (298/528 segments). With gated SPECT, LVEF, end-diastolic volume (EDV), and end-systolic volume (ESV) were 27+/-9%, 217+/-77 mL, and 163+/-73 mL, respectively, and 30+/-8%, 195+/-58 mL, and 137+/-48 mL with echocardiography. The correlation between gated SPECT and 2D-echocardiography was good (r=0.76, P<0.01) for the assessment of LVEF. The correlation for EDV and ESV were also good, but with wider limits of agreement (r=0.72, P<0.01 and r=0.73, P<0.01, respectively) and significantly higher values were obtained with gated SPECT (P<0.01).

CONCLUSIONS

Gated SPECT and 2D-echocardiography correlate well for the assessment of LV function and LV volumes. Like 2D-echocardiography, gated SPECT provides reliable information about LV function and dimension with the additional advantage of perfusion data.

Improved accuracy in estimation of left ventricular function parameters from QGS software with Tc-99m tetrofosmin gated-SPECT: a multivariate analysis

The purpose of this study was to verify whether the accuracy of left ventricular parameters related to left ventricular function from gated-SPECT improved or not, using multivariate analysis.

METHODS

Ninety-six patients with cardiovascular diseases were studied. Gated-SPECT with the QGS software and left ventriculography (LVG) were performed to obtain left ventricular ejection fraction (LVEF), end-diastolic volume (EDV) and end-systolic volume (ESV). Then, multivariate analyses were performed to determine empirical formulas for predicting these parameters. The calculated values of left ventricular parameters were compared with those obtained directly from the QGS software and LVG.

RESULTS

Multivariate analyses were able to improve accuracy in estimation of LVEF, EDV and ESV. Statistically significant improvement was seen in LVEF (from r = 0.6965 to r = 0.8093, p < 0.05). Although not statistically significant, improvements in correlation coefficients were seen in EDV (from r = 0.7199 to r = 0.7595, p = 0.2750) and ESV (from r = 0.5694 to r = 0.5871, p = 0.4281).

CONCLUSION

The empirical equations with multivariate analysis improved the accuracy in estimating LVEF from gated-SPECT with the QGS software.

Compared with 3-dimensional analysis, 2-dimensional gated SPECT analysis overestimates left ventricular ejection fraction in patients with regional dyssynchrony

BACKGROUND

Left ventricular (LV) ejection fraction (EF) is a powerful prognostic predictor in patients with heart disease. However, LVEF calculated by 2-dimensional (2D) modalities such as echocardiography by use of the "modified" Simpson's rule may be incorrect in patients with regional dyssynchrony, presumably because regions of dyssynchrony are excluded from analysis.

METHODS AND RESULTS

To elucidate the difference between 2D and 3-dimensional (3D) methods with regard to LVEF calculation in patients with regional dyssynchrony, we compared LVEF derived from 8-frame gated technetium 99m sestamibi stress perfusion tomograms using commercially available 2D single photon emission computed tomography (SPECTEF) software that uses the modified Simpson's rule, 3D QGS, and investigational 3D p-FAST software in 136 left bundle branch block patients. Twenty-four patients had normal wall motion, whereas one hundred twelve showed septal dyssynchrony. Bland-Altman plots demonstrated that compared with QGS and p-FAST, SPECTEF overestimated LVEF in patients with septal dyssynchrony systemically by 8.6% and 11.3%, respectively.

CONCLUSIONS

We conclude that compared with 3D modalities, 2D modalities that use the modified Simpson's rule, such as SPECT EF, overestimate LVEF in patients with dyssynchronous septal wall motion. Therefore 3D modalities are preferred to evaluate patients with regional dyssynchrony.

Day-to-day variability of global left ventricular functional and perfusional measurements by quantitative gated SPECT using Tc-99m tetrofosmin in patients with heart failure due to coronary artery disease

BACKGROUND

Although myocardial gated single photon emission computed tomography (SPECT) is routinely used for functional measurements in patients with coronary artery disease (CAD) and heart failure, day-to-day variability of left ventricular ejection fraction (LVEF), left ventricular (LV) volumes, and global perfusion scoring has not yet been investigated.

METHODS AND RESULTS

In 20 consecutive patients with CAD and an LVEF lower than 40% who routinely underwent a resting tetrofosmin gated SPECT study, we performed an additional gated SPECT study at rest 1 to 5 days later under the same circumstances. LV volumes and LVEF were calculated from the gated SPECT data by commercially available software (QGS). Myocardial perfusion was scored visually by use of a 20-segment, 5-point scoring method. For global LV function and perfusion, agreement between data was investigated by use of Bland-Altman plotting. The 95% limits of agreement found by Bland-Altman analysis were -0.9% +/- 6.0% for LVEF, 3 +/- 20 mL for LV end-diastolic volume, and 4 +/- 20 mL for LV end-systolic volume.

CONCLUSION

In CAD patients with an LVEF lower than 40%, day-to-day variability of measurements of global myocardial function and perfusion is quite similar to interobserver and intraobserver variability. Day-to-day variability of global LV functional parameters obtained by gated cardiac SPECT is fairly small, which indicates that myocardial gated SPECT can be used in daily clinical practice to determine changes in global LV function and perfusion over time in patients with diminished LV function.

Autologous bone marrow-derived progenitor cell transplantation for myocardial regeneration after acute infarction

Background. Experimental and first clinical studies suggest that the transplantation of bone marrow derived, or circulating blood progenitor cells, may beneficially affect postinfarction remodelling processes after acute myocardial infarction. Aim. This pilot trial reports investigation of safety and feasibility of autologous bone marrow-derived progenitor cell therapy for faster regeneration of the myocardium after infarction. Methods and results. Four male patients (age range 47-68 years) with the first extensive anterior, ST elevation, acute myocardial infarction (AMI), were treated by primary angioplasty. Bone marrow mononuclear cells were administered by intracoronary infusion 3-5 days after the infarction. Bone marrow was harvested by multiple aspirations from posterior cristae iliacae under general anesthesia, and under aseptic conditions. After that, cells were filtered through stainless steel mesh, centrifuged and resuspended in serum-free culture medium, and 3 hours later infused through the catheter into the infarct-related artery in 8 equal boluses of 20 ml. Myocardial viability in the infarcted area was confirmed by dobutamin stress echocardiography testing and single-photon emission computed tomography (SPECT) 10-14 days after infarction. One patient had early stent thrombosis immediately before cell transplantation, and was treated successfully with second angioplasty. Single average ECG revealed one positive finding at discharge, and 24-hour Holter ECG showed only isolated ventricular ectopic beats during the follow-up period. Early findings in two patients showed significant improvement of left ventricular systolic function 3 months after the infarction. There were no major cardiac events after the transplantation during further follow-up period (30-120 days after infarction). Control SPECT for the detection of ischemia showed significant improvement in myocardial perfusion in two patients 4 months after the infarction. Echocardiographic assessment in these two patients also showed significant improvement of systolic function three months after the infarction. Conclusion. Preliminary results of the study showed that the transplantation of bone marrow-derived progenitor cells into the infarcted area was safe, and feasible, and might improve myocardial function. Further follow-up will show if this treatment is effective in preventing negative remodeling of the left ventricle and reveal potential late adverse events (arrhythmogenicity and propensity for restenosis).

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.