Clinical validation of simultaneous dual-isotope myocardial scintigraphy

Abstract.

Simultaneous dual-isotope (rest thallium-201/stress technetium-99m sestamibi) myocardial single-photon emission tomography (SPET) would be an ideal procedure; however, ^99mTc cross-talk on the ²⁰¹Tl window hampers its routine use. Photon energy recovery (PER) is a spectral deconvolution technique validated for scatter and cross-talk removal in phantom studies and a limited series of patients. In this study we aimed to validate the technique in 295 patients within a context of clinical routine practice. Conventional separate rest ²⁰¹Tl myocardial SPET data sets were visually compared with simultaneous dual-isotope data sets corrected by PER. Conventional separate rest ²⁰¹Tl data sets were identical to dual PER-corrected ²⁰¹Tl data sets in 173 (58.6%) patients. As dual PER ²⁰¹Tl data sets are corrected for ^99mTc cross-talk but also for ²⁰¹Tl scatter, they were compared with separate rest ²⁰¹Tl data sets corrected by PER in the 122 discordant patients. No difference was found in 77 (26.1%) patients. In 26 (8.8%) patients, the difference consisted in the presence of a defect on dual PER ²⁰¹Tl data sets only, mirroring an ischaemic defect on ^99mTc-sestamibi data sets. This difference can be attributed to the influence of stress on the kinetics of ²⁰¹Tl injected at rest. In the remaining 19 (6.4%) patients, the difference between separate and simultaneous PER-corrected data sets was scored as mild in 11 and moderate in eight patients and seemed to be related to multiple methodological factors. It is concluded that PER correctly removes ^99mTc cross-talk. With the addition of an appropriate attenuation correction, the PER technique may allow the routine use of simultaneous dual-isotope myocardial scintigraphy in the near future.