Reproducibility of radionuclide gated cardiac blood pool imaging (GBPI) in left ventricular ejection fraction (LVEF) assessment in infarcted patients and a healthy young control population

The aim of this study was to evaluate the reproducibility of two different gamma-camera-computer systems in assessment of LVEF in two different clinical groups of patients. Patients and Method: We performed GBPI to 27 individual: 14 infarcted patients (age average:62.1 yr, range:44-91 yr) with a mean LVEF of 33.6% (range:15%-49%) and 13 healthy young controls (age average:19.0 yr, range: 17-22 yr) with a mean LVEF of 61.2% (range:53%-67%), using two different gamma-cameras. Each individual was injected once with 25 mCi of in vitro labelled Tc99m red blood cells performing a rest 24 frames GBPI study with a Picker Dyna 4/15 gamma-camera linked to a computer system, and immediately after with a SMV DST XLi gamma-camera, collecting in each study 300,000 counts per frame. Before starting acquisition, the best left anterior oblique was determined (optimal ventricular separation), usually 450, using the same angle in the second gamma-camera acquisition. GBPI were processed with the standard semiautomatic (Picker) and automatic (SMV) programs available, getting 10 LVEF measurements for each patient, and calculating the average and SD for each of them. For reproducibility assessment, the variability coefficient (VC) was calculated for each patient according to the algorism: VC=SD x 100/average, being the mean and SD of this coefficient compared between both clinical and gamma-camera group. Results: In control group there was not significant difference between the variability of LVEF calculated with Picker (VC:2.30,SD:1,24) and SMV (VC:2.07,SD:0.62) equipment. Correlation was of 0.765 (p:0.004) between both gamma-cameras. In infarcted patients, the variability between Picker (VC:3.47,SD:2.39) and SMV (VC:3.51,SD:1.72) was similar as well, with a correlation of 0.969 (p<0.001) between both equipment. When we compared the variability of the same gamma-camera in different clinical groups, only the SMV showed significant difference, with lower variability in control group than in infarcted group (p:0.011). The global correlation between both gamma-cameras was 0.97. Conclusion: 1) Reproducibility of both gamma-camera-computing systems is very high. 2) Variability in SMV gamma-camera measurements is greater in infarcted patients than in control individuals