Validity of 18F-fluorodeoxyglucose imaging with a dual-head coincidence gamma camera for detection of myocardial viability.

This study investigated the validity of myocardial 18F-fluorodeoxyglucose (FDG) imaging with a dual-head gamma camera operated in coincidence detection mode (DCD-I) by comparing this technique with conventional PET and SPECT with ultra-high-energy general-purpose collimators (UHGPs). METHODS: The subjects included 5 healthy volunteers and 20 patients with a history of myocardial infarction. FDG (370 MBq) was injected intravenously after 75-g oral glucose loading, and PET, UHGP SPECT and DCD-I were performed 45, 60 and 210 min, respectively, after the injection. The target-to-background ratio of each imaging method was evaluated for the healthy volunteers by comparing myocardial uptake with uptake in the upper lungs or left ventricular cavity. Agreement between the results of the various imaging methods was investigated for the myocardial infarction patients, as was the validity of DCD-I for assessing myocardial viability as judged by comparison with myocardial perfusion SPECT. The left ventricular wall was divided into 18 regions, and uptake was evaluated using a five-grade defect score (0 = normal; 1-3 = low uptake; 4 = defect). RESULTS: The mean ratio of myocardial counts to lung counts was lower on the DCD images (2.77 +/- 1.12) than on the UHGP SPECT images (3.69 +/- 0.98) (P < 0.05). In contrast, the mean ratio of myocardial counts to left ventricular cavity counts was higher on the DCD images (2.76 +/- 1.36) than on the UHGP SPECT images (1.98 +/- 0.70) (P < 0.05). For the patients, only 30.6% of the defect scores obtained by DCD-I agreed with the scores obtained by PET, and the defect scores in the inferior and septal walls were higher for the DCD images than for the PET images. When DCD-I was compared with PET without attenuation correction (AC), agreement improved to 58.3%. When corrected by a modified AC method, DCD-I improved to 48.1%. Agreement between UHGP SPECT and PET was 55.0%. Of the segments (64) for which the defect score of the myocardial perfusion image was greater than that for the FDG PET image, DCD-I without AC, DCD-I with AC and UHGP SPECT allowed an accurate diagnosis in 12 (18.8%), 31 (48.4%) and 43 (67.2%), respectively. CONCLUSION: The image quality of DCD-I is superior to that of UHGP SPECT. However, because the effect of attenuation is marked, accurate AC, by the transmission method, for example, is required to equal the validity of PET.