Objective To evaluate whether low carbohydrate diet before 18F-FDG tumor imaging could reduce myocardial 18F-FDG uptake.Methods From April 2011 to January 2012,70 patients were enrolled in this study.They were randomly divided into control group (34 cases) and test group (36 cases).Patients in control group were on regular diet,while those in test group had low carbohydrate diet in the evening before imaging.Blood samples were taken before injection of 18F-FDG for the measurement of serum glucose,free fatty acid,insulin and ketone body.Whole body 18F-FDG tomography was performed with dualhead coincidence SPECT.The myocardial uptake of FDG was assessed visually and scored as 0 for no uptake,1 for uptake lower than liver,2 for uptake similar to liver,3 for uptake higher than liver,and 4 for remarkable uptake.The ratio of myocardium to liver (H/L) was calculated.Two-sample t test,Wilcoxon rank sum test and linear correlation analysis were performed.Results The myocardial uptake in test group was significantly lower than that in control group with H/L ratios of 0.94±0.57 and 1.50±1.04,respectively(t=-2.75,P＜0.05).The concentrations of serum free fatty acid and ketone body in test group were significantly higher than those in control group: (0.671±0.229) mmol/L vs (0.547±0.207) mmol/L and (0.88±0.60) mmol/L vs (0.57±0.32) mmol/L,t=2.38 and 2.67,both P＜0.05.The concentrations of glucose and insulin were (5.28±1.06) mmol/L and (35.16±33.70) pmol/L in test group,which showed no significant difference with those in control group ((5.19±0.78) mmol/L and (41.64±35.13) pmol/L,t=0.39 and-0.79,both P＞0.05).A negative correlation was found between the myocardial uptake of 18F-FDG and serum free fatty acid/ketone body concentration (r=-0.40,-0.33,both P＜0.01),respectively.There was no correlation between the myocardial uptake of 18 F-FDG and glucose/insulin (r =-0.02,0.13,both P＞0.05),respectively.Conclusion Low carbohydrate diet before 18F-FDG tumor imaging can reduce myocardial uptake,thus facilitating detection of lesions near the heart.