Comparison of correction techniques for simultaneous²⁰¹Tl/^99mTc myocardial perfusion SPECT imaging: a dog study

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 placed between the photopeak windows of the 201Tl and 99mTc. The first approach, described by Moore et al, corrects only for the contribution of the 99mTc to the 201Tl primary 70 keV window. We developed the three-window transformation dual isotope correction method, which is a simultaneous cross-talk correction. The two correction methods were compared in a simultaneous 201Tl/99mTc sestamibi cardiac dog study. Three separate acquisitions were performed in this dog study: two single-isotope and one dual-isotope acquisition. The 201Tl single-isotope images were used as references. The total number of counts, and the contrast between the left ventricular cavity (LVC) and the myocardium, were used in 70 keV short axis slices as parameters for evaluating the results of the dual-isotope correction methods. Three consecutive short-axis slices were used to calculate averaged contrast and the averaged total number of counts. The total number of the counts was 667000+/-500 and 414500+/-400 counts for the dual isotope (201Tl+/-99mTc) and single-isotope (201Tl-only) 70 keV images, respectively. The corrected dual-isotope images had 514700+/-700 and 368000+/-600 counts for Moore's correction and our approach, respectively. Moore's method improved contrast in the dual isotope 70 keV image to 0.14+/-0.03 from 0.11+/-0.02, which was the value in the 70 keV non-corrected dual-isotope image. Our method improved the same contrast to 0.22+/-0.03. The contrast in the 201Tl single-isotope 70 keV image was 0.28+/-0.02. Both methods improved the 70 keV dual-isotope images. However, our approach provided slightly better images than Moore's correction when compared with 201Tl-only 70 keV images.

Review and current status of SPECT scatter correction

“…Multiple energy windows can be used, estimating scatter in each photo-peak energy window based on projections acquired in other energy windows, either using adaptations of the TEW approach (e.g. Matsudaira et al 1997) or using convolution models to derive the relationship between the primary and scatter projections recorded in different energy windows (Moore et al 1995, Knesaurek andMachac 2000). A set of simultaneous equations can be established to describe the various components in each of several energy windows and these can be used to derive scatter-free photo-peak projections using artificial neural networks (El Fakhri et al 2001), spectral factor analysis (Hapdey et al 2006) or maximum likelihood estimation (Kacperski et al 2011).…”

Tc99m/T1201 cross-talk corrections on a dedicated cardiac CZT SPECT camera

“…As previously discussed, an obstacle to multi-isotope imaging is the presence of cross-talk. Many scatter correction methods have been applied to dual-isotope studies with traditional cameras (5,64) including the Tc99m-T1201 isotope combination that we focus on in this work (10,12,65). In a recent study by Ben-Haim et al (3), dual-isotope imaging was studied on a different type of dedicated cardiac camera that uses the same CZT-based solid-state detectors (D-SPECT, Spectrum Dynamics).…”

“…This leads to a total time of approximately four hours for a same-day rest-stress Tc99m acquisition, due to the wait needed between acquisitions to minimize interference of the tracer from the first injection in the second image. (2) SPECT offers the possibility o f performing simultaneous dual-isotope imaging (3)(4)(5)(6)(7)(8), as multiple isotopes can be used for the same study. Proposed protocols in can reduce the total time to 30 minutes as well as having many more advantages.…”