[ 18 F]Fluorodeoxyglucose Single Photon Emission Computed Tomography

Abstract

Background —New high-energy collimators for single photon emission computed tomography (SPECT) cameras have made imaging of positron-emitting tracers, such as [ 18 F]fluorodeoxyglucose ( 18 FDG), possible. We examined differences between SPECT and PET technologies and between 18 FDG and thallium tracers to determine whether 18 FDG SPECT could be adopted for assessment of myocardial viability. Methods and Results —Twenty-eight patients with chronic coronary artery disease (mean left ventricular ejection fraction [LVEF]=33±15% at rest) underwent 18 FDG SPECT, 18 FDG PET, and thallium SPECT studies. Receiver operating characteristic curves showed overall good concordance between SPECT and PET technologies and thallium and 18 FDG tracers for assessing viability regardless of the level of 18 FDG PET cutoff used (40% to 60%). However, in the subgroup of patients with LVEF≤25%, at 60% 18 FDG PET threshold value, thallium tended to underestimate myocardial viability. In a subgroup of regions with severe asynergy, there were considerably more thallium/ 18 FDG discordances in the inferior wall than elsewhere (73% versus 27%, P <.001), supporting attenuation of thallium as a potential explanation for the discordant observations. When uptake of 18 FDG by SPECT and PET was compared in 137 segments exhibiting severely irreversible thallium defects (scarred by thallium), 59 (43%) were viable by 18 FDG PET, of which 52 (88%) were also viable by 18 FDG SPECT. However, of the 78 segments confirmed to be nonviable by 18 FDG PET, 57 (73%) were nonviable by 18 FDG SPECT ( P <.001). Conclusions —Although 18 FDG SPECT significantly increases the sensitivity for detection of viable myocardium in tissue declared nonviable by thallium (to 88% of the sensitivity achievable by PET), it will occasionally (27% of the time) result in falsely identifying as viable tissue that has been identified as nonviable by both PET and thallium.