Original ArticleComparison of three commercially available softwares for measuring left ventricular perfusion and function by gated SPECT myocardial perfusion imaging
Introduction
ECG-gated myocardial perfusion imaging (MPI) with single-photon emission-computed tomography (SPECT) is the most widely used imaging modality in the diagnosis and risk assessment of patients with ischemic heart disease.1, 2, 3 MPI generates information on myocardial perfusion [reversible defects (ischemia) and fixed defects (scar)], left ventricle (LV) ejection fraction (EF), volumes, mass, regional wall motion, and thickening. The visual interpretation of MPI is dependent on observer’s expertise and is less reproducible than automated methods.4,5 There are three widely used commercial softwares for automated measurements; Quantitative Perfusion SPECT (QPS, Cedars-Sinai Medical Center, Los Angeles, CA, USA), Emory Cardiac Toolbox (ECTb, Emory University, Atlanta, GA, USA), and 4 Dimension-Myocardial SPECT (4DM, University of Michigan, Ann Arbor, MI, USA).
Several studies have demonstrated that the above mentioned softwares have a strong correlation with each other, and with an independent “gold standard” in estimating LV function and volumes.6, 7, 8, 9, 10, 11, 12, 13 In contrast, there are limited data on the degree of agreement between these programs in assessing perfusion abnormalities,5,14, 15, 16 and no data regarding agreement of the three softwares in measuring perfusion defect size (PDS) and the size of reversible perfusion defects using polar maps.
The aim of this study was to examine the correlation and agreement between the three programs in assessing PDS, and reversible defect size (by polar maps) as well as LVEF, end-diastolic volume (EDV), end-systolic volume (ESV), and mass.
Section snippets
Study Population
Data were collected from 120 consecutive patients who had abnormal regadenoson MPI with a visual SSS ≥4 performed between July and September 2008 at University of Alabama at Birmingham Medical Center. All studies were performed using a stress/rest sestamibi protocol, in which MPI data were acquired without attenuation correction. The Institutional Review Board for Human Research at the University of Alabama at Birmingham approved this study.
Imaging Protocol
SPECT images were acquired and processed using
Results
A total of 120 consecutive patients were included in the study. The baseline characteristics of the patients are detailed in Table 1 and are significant for the presence of multiple co-morbidities with a large proportion receiving multiple cardiac medications.
The inter-observer reproducibility of the results was strong for all variables measured using each of the softwares. The ICC ranged from 0.86 to 1.0 for assessment of LVEF, volumes, and mass, and from 0.94 to 0.99 for assessment of PDS
Discussion
An important finding from our study is that for the assessment of PDS and reversible perfusion defects (fixed defects are derived as PDS-reversible defects), the correlation between QPS, ECTb, and 4DM is poor to fair. For measurement of PDS, QPS exhibited a systematic bias toward lower values and 4DM toward higher values. For measurement of reversible defect size, 4DM showed a systematic bias toward higher values than the other two programs. For assessment of LV volumes and function, there was
Conclusions
Although the three softwares produce highly reproducible results for automated measurements of PDS and reversible perfusion defects, the correlation between the softwares is only fair to poor. Importantly, the softwares provided discrepant results for important end-points of moderate to severe PDS and reversible perfusion defect, in a large proportion of patients. The softwares provided discrepant results in a smaller, but still clinically significant, proportion of patients for assessment of
New Knowledge Gained
There is significant discordance among the three widely used commercial softwares in assessing PDS. This discordance is due to systematic bias and significant random error. In contrast, there is strong correlation between the softwares for assessment of LV size and function. Further, there is significant discordance among the softwares in categorizing perfusion defects into small, moderate or large. The corresponding discordance in categorizing LVEF into normal, mild-moderate and severe
Conflict of interest
The authors have indicated that they have no financial conflict of interest.
Disclosure
Dr Iskandrian is a scientific advisor for Rapidscan, Pharma and has received research grants from Astellas Pharma USA. Dr Hage is a scientific advisor for Astellas Pharma USA and has received investigator-initiated grant support from Astellas Pharma USA. The other authors report no financial disclosures.
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Sameer Ather and Fahad Iqbal have contributed equally to this manuscript.