Comparison of correction techniques for simultaneous201Tl/99mTc myocardial perfusion SPECT imaging: a dogstudy

Abstract

We compared two correction methods for simultaneous 201Tl/99mTc dual-isotope single-photon emission computed tomography (SPECT).Both approaches use the information from the third energy window placedbetween the photopeak windows of the 201Tl and 99mTc. The first approach, described by Moore et al, corrects only for thecontribution of the 99mTc to the 201Tl primary70 keV window. We developed the three-window transformation dual-isotopecorrection method, which is a simultaneous cross-talk correction. The twocorrection methods were compared in a simultaneous 201Tl/99mTc sestamibi cardiac dog study. Three separate acquisitions wereperformed in this dog study: two single-isotope and one dual-isotopeacquisition. The 201Tl single-isotope images were used asreferences. The total number of counts, and the contrast between the leftventricular cavity (LVC) and the myocardium, were used in 70 keV short-axisslices as parameters for evaluating the results of the dual-isotope correctionmethods. Three consecutive short-axis slices were used to calculate averagedcontrast and the averaged total number of counts. The total number of thecounts was 667 000 ± 500 and 414 500 ± 400 counts for the dual-isotope(201Tl + 99mTc) and single-isotope (201Tl-only) 70 keV images, respectively. The corrected dual-isotope images had514 700 ± 700 and 368 000 ± 600 counts for Moore's correction and ourapproach, respectively. Moore's method improved contrast in the dual-isotope70 keV image to 0.14 ± 0.03 from 0.11 ± 0.02, which was the value in the70 keV non-corrected dual-isotope image. Our method improved the same contrastto 0.22 ± 0.03. The contrast in the 201Tl single-isotope 70 keVimage was 0.28 ± 0.02. Both methods improved the 70 keV dual-isotope images.However, our approach provided slightly better images than Moore's correctionwhen compared with 201Tl-only 70 keV images.