[F-18] FLUORODEOXYGLUCOSE SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY - CAN IT REPLACE PET AND THALLIUM SPECT FOR THE ASSESSMENT OF MYOCARDIAL TOMOGRAPHY

Background-New high-energy collimators for single photon emission comp uted tomography (SPECT) cameras have made imaging of positron-emitting tracers, such as [F-18]fluorodeoxyglucose ((18)FDG), possible. We exa mined differences between SPECT and PET technologies and between (18)F DG and thallium tracers to determine whether (18)FDG SPECT could be ad opted for assessment of myocardial viability. Methods and Results-Twen ty-eight patients with chronic coronary artery disease (mean left vent ricular ejection fraction [LVEF]=33+/-15% at rest) underwent (18)FDG S PECT, (18)FDG PET, and thallium SPECT studies. Receiver operating char acteristic curves showed overall good concordance between SPECT and PE T technologies and thallium and (18)FDG tracers for assessing viabilit y regardless of the level of (18)FDG PET cutoff used (40% to 60%). How ever, in the subgroup of patients with LVEF less than or equal to 25%, at 60% (18)FDG PET threshold value, thallium tended to underestimate myocardial viability. In a subgroup of regions with severe asynergy, t here were considerably more thallium/(18)FDG discordances in the infer ior wall than elsewhere (73% versus 27%, P<.001), supporting attenuati on of thallium as a potential explanation for the discordant observati ons. When uptake of (18)FDG by SPECT and PET was compared in 137 segme nts exhibiting severely irreversible thallium defects (scarred by thal lium), 59 (43%) were viable by (18)FDG PET, of which 52 (88%) were als o 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). Conclusion-Although (18)FDG SPECT significantly increases the sensitivity for detection of viable myocardium in tissue declared nonv iable by thallium (to 88% of the sensitivity achievable by PET), it wi ll occasionally (27% of the time) result in falsely identifying as via ble tissue that has been identified as nonviable by both PET and thall ium.