ABSTRACT
Background: The voxel size in ECG-gated myocardial SPECT (GSPECT) is a compromise between geometric resolution and count statistics with varying values and is rather inconsistent in different centers. We investigated the influence of typical acquisition matrix sizes for GSPECT on the reproducibility and accuracy of left ventricular function parameters using a dynamic heart phantom. Methods: Ten paired acquisitions, each pair with slightly different phantom positions, were obtained using identical imaging parameters except acquisition matrix: 128 × 128 matrix (3.3 mm voxel) and 64 × 64 matrix (6.6 mm voxel). In the next step, 128 × 128 data sets were compressed to an additional set of 64 × 64 matrix images. Results: Nominal value of left ventricular ejection fraction (LVEF) of the phantom was 67%. Both acquisition matrices led to significant overestimation of the LVEF. Overestimation was more pronounced in 64 × 64 than in 128 × 128 studies (79.8 ± 2.5% vs. 73.6 ± 1.4%, p<0.05). Calculated volumes were closer to the nominal values with 128 × 128 than with 64 × 64 studies. Variance showed a trend to be higher with 64 × 64 matrix, but the effect did not reach the level of statistical significance. Conclusions: LVEF overestimation and volume underestimation can be reduced by using finer matrix size without any negative effect on the reproducibility.
ABSTRACT
Background: In myocardial gated single-photon emission computed tomography (GSPECT), to differentiate true changes of left ventricular ejection fraction (LVEF) from inherent methodical variability is clinically relevant; however, data about repeatability of GSPECT LVEF in the same patients are rather inconsistent in literature. The aim of this study was therefore to determine repeatability coefficient (RC) of GSPECT LVEF at rest and to investigate the effect of the introduction of processing constraints in left ventricular edge detection. Methods: Thirty-five patients referred for one-day myocardial GSPECT stress-rest scan were included. After the routine stress-rest study, patients were completely repositioned on the imaging table for a second rest acquisition using the same acquisition parameters. LVEF was computed using Corridor 4DM software without and with manual alignment of valve plane. Repeatability was assessed using the Bland-Altman method. Results: RC of LVEF from unaligned datasets was 7.6% with upper and lower limits of agreement of 7.4% to -7.8%. After valve plane and ventricular long-axis length alignment, RC improved to 3.6% with upper and lower limits of agreement of 3.4% to -3.8%. Conclusions: RC using unaligned determination of GSPECT LVEF was comparable to that from previous publications. However, RC using valve plane alignment could be improved to below 4% on 95% confidence level.
