Abstract
1915
Objectives FDGPET/CT plays an important role to diagnose inflammatory (e.g., sarcoidosis) heart diseases.However, physiological FDG uptake isfrequently observed in myocardium, which degrades the diagnostic value of the examination. Recently, volume based analysis of the FDG uptake has been used mainly in oncological studies. However, there have been few reports about volume based analysis of physiological myocardial accumulation and its correlation with clinical status. Thus, our first aim of this study was to determine the optimum threshold to quantify the volume based analysis. The second aim was to quantify the regional and whole cardiac uptake of FDG compared with the several clinical factors.
Methods This retrospective study included a total of 94 patients (62.6 ±12.4 years old, 51 males) who underwent FDG PET/CT in order to examine known or suspected malignant tumors. At first, two physicians independently set a 1-cm-in-diameter spherical volume-of-interest (VOI) in the descending aorta and the left ventricle (LV) cavity to compare the inter-operator reproducibility in 30 patients. Cardiac metabolic volume (CMV) was defined as a volume within the boundary determined using the threshold. SUVmax and CMV were calculated in the whole left ventricle as well as in the 17 segments of AHA model. CMV were compared with clinical factors including age, sex, body mass index (BMI), fasting period (18h), fasting blood sugar (FBS), and hospitalization status (inpatient vs. outpatient).
Results The SUVmean from the descending aorta showed significantly higher inter-operator reproducibility than that from blood pool of the LV (ICC = 0.78 vs. 0.66, respectively). Therefore, we adopted use of [SUVmean in the descending aorta]×1.5as the delineation threshold of cardiac uptake. The CMV and fasting period showed relationship (p < 0.05, ANOVA), whole-heart CMV was significantly lower in the patients over 15 hours fasting compare than in the others (48.12±78.67[ml] vs. 79.68±94.76[ml], p<0.05). The frequency of zero CMV was significantly higher in the patients of longer fasting (56.0% vs. 31.8 %, p = 0.042). Neither BMI nor FBS showed relationship to the whole-heart CMV (p = NS). Whole-heart CMV of the outpatients was significantly higher than that of the inpatients (69.5. ± 89.6 [ml] vs.36.6 ± 74.8[ml], p = 0.05). For the regional analysis, the uptake volume in the lateral wall tended to be higher, but there were no significant differences among the anterior, septal and inferior wall at each fasting duration (Table1 and Table2).
Conclusions We conducted the quantitative analysis of the cardiac FDG accumulation in cancer patients. The threshold should be determined from the descending aorta rather than from the LV cavity, based on the high inter-operator reliability. The fasting time was significantly correlated with the whole-heart CMV. The regional analysis demonstrated that the lateral wall uptake was significantly greater at each fasting time and any hospitalization statuses. Therefore, volume based analysis of cardiac disease may identify characteristics of physiological myocardial FDG uptake and may hold a potential role to identify abnormal myocardial uptake.