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

This study investigated the validity of myocardial F-18-fluorodeoxyglucose (FDG) imaging with a dual-head gamma camera operated in coincidence detecti on mode (DCD-I) by comparing this technique with conventional PET and SPECT with ultra-high-energy general-purpose collimators (UHGPs). Methods: The s ubjects included 5 healthy volunteers and 20 patients with a history of myo cardial infarction. FDG (370 MBq) was injected intravenously after 75-g ora l 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 comparin g myocardial uptake with uptake in the upper lungs or left ventricular cavi ty. Agreement between the results of the various imaging methods was invest igated 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, an d uptake was evaluated using a five-grade defect score (0 = normal; 1-3 = l ow uptake; 4 = defect). Results: The mean ratio of myocardial counts to lun g 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 myocardi al 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 sept al walls were higher for the DCD images than for the PET images. When DCD-I was compared with PET without attenuation correction (AC), agreement impro ved 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) fo r 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%), re spectively. Conclusion: The image quality of DCD-I is superior to that of U HGP SPECT. However, because the effect of attenuation is marked, accurate A C, by the transmission method, for example, is required to equal the validi ty of PET.