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Objective To study the ambient radiation of patients undergoing 18F-FDG PET/CT myocardial metabolism imaging, and to provide data for protection of surrounding people against radiation. Methods A total of 33 patients were selected for 18F-FDG PET/CT myocardial metabolism imaging. Dose equivalent rate was measured at the height of patient chest, in different directions, at different time points and at different distances, to investigate the distribution of ambient radiation of the patient. Results At the same time point and distance, the dose equivalent rates at the left and right sides of the patient were lower than the front and back sides. The dose equivalent rate at 1 m in front of the patient was 13-21 μSv/h after 18F-FDG injection, and decreased to 5-14 μSv/h after PET/CT imaging, with a mean decrease of 46%. The ambient dose equivalent rate decreased exponentially with distance (10~300 cm), and the mean power was −1.2. Conclusion The ambient radiation of patients undergoing 18F-FDG PET/CT myocardial metabolism imaging was high after 18F-FDG injection, and the ambient dose equivalent rate decreased rapidly with time and distance. Our results suggest that patients undergoing myocardial metabolism imaging should avoid prolonged and close contact with other people on the day of examination.
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Objective:To evaluate the image quality (IQ) of 18F-fluorodeoxyglucose (FDG) PET/CT imaging and identify its influenfial factors in diabetes mellitus (DM) and non-DM patients with coronary artery disease (CAD). Methods:A total of 196 consecutive CAD patients (174 males, 22 females, 68 DM; age: (57±10) years) in Beijing Anzhen Hospital between June 2016 and February 2018 were retrospectively analyzed. All patients underwent 18F-FDG myocardial PET/CT imaging. The standardized fasting+ oral glucose loading (OGL) and intravenously injection of insulin protocol was performed. According to the FDG uptake by myocardium, background activity in blood and other visceral organ nearby the heart, the IQ was visually evaluated and scored by 0-4. Zero-two was considered as good IQ, 3-4 was regarded as poor IQ. Patients were divided into three groups: group 1 (non-DM+ good IQ), group 2 (DM+ good IQ), group 3 (DM+ poor IQ). Factors which may affect IQ were analyzed, which including OGL, the injection dose of insulin, fasting blood glucose (FBG), peak blood glucose (PBG), blood glucose (BG) level at 18F-FDG injection (BG injnection), BG increasing rate ((PBG-FBG)/FBG, %), and BG decreasing rate ((PBG-BG injection)/PBG, %). One-way analysis of variance, Spearman correlation analysis and logistic regression analysis were used for data analysis. Results:There were significant differences ( F values: 13.074-38.371, all P<0.05) of FBG, PBG, OGL, BG decreasing rate and the injection dose of insulin among group 1 ( n=132, 67.3%), group 2 ( n=53, 27.1%), group 3 ( n=11, 5.6%). All those parameters, except for OGL, were positively correlated with FDG PET/CT IQ ( r s values: 0.142-0.262, all P<0.05). OGL was negatively correlated with IQ ( r s=-0.324, P<0.05). Logistic regression analysis showed that FBG (odds ratio ( OR)=0.687, 95% CI: 0.633-0.746), PBG( OR=0.786, 95% CI: 0.746~0.829), BG injection( OR=0.631, 95% CI: 0.595-0.716), OGL( OR=0.897, 95% CI: 0.873-0.922), the injection dose of insulin( OR=0.680, 95% CI: 0.618-0.748) were predictive factors (all P<0.01) for good IQ in all patients. For DM patients, OGL was the only predictive factor for good IQ( OR =0.940, 95% CI: 0.904-0.960; P<0.01). Conclusions:FBG, PBG, BG injection, OGL, the injection dose of insulin can predict IQ for all patients with CAD. For DM patients with CAD, OGL is the only predictive factor for good IQ. A good IQ of 18F-FDG PET/CT could be obtained in majority of CAD patients, with the standardized fasting + OGL and intravenously injection of insulin protocol and adjust according to the personal status, and prevent the hypoglycemia from happening.