¹¹C-acetate PET/CT Imaging In Diagnosis Of Primary Hepatic Carcinoma

ObjectiveThe purpose of this study is to investigate the value of 11C-acetate PET/CT scan, compared with 18F-FDG PET/CT scan and CT enhancement scanning, for the diagnosis of primary hepatic carcinoma. Materials and Methods31 patients (43 lesions) which were suspicious of hepatic carcinoma were collected between Apr,2008 and Apr,2010, which included 31 HCC lesions,19 of them were confirmed by histopathologically,12 of them were confirmed by clinical diagnosis and follow-up, other 12 non-HCC lesions were all confirmed by histopathologically.31 patients underwent whole-body 18F-FDG PET/CT scan and abnorminal 11C-acetate PET/CT scan in two weeks, and 29 of them underwent CT enhancement scanning,6 of them underwent MR enhancement scanning. No treatment was performed in this period. Two cases of HCC with portal vein invasived were confirmed histopathologically, which underwent whole-body 18F-FDG PET/CT scan and abnorminal 11C-acetate PET/CT scan, abnorminal CT enhancement scanning and CT angiography. Another two cases with history of ectomy for liver cancer and secondary liver implantation and treatment for multiple metastases underwent whole-body11C-acetate PET/CT scan, one of them underwent 18F-FDG PET/CT scan, increasing alpha-fetoproteins concentration were found in these two patients after ectomy.For semiquantitative analysis, the tumor-to-liver ratio (target-background ratio, T/B) was calculated by dividing the maximal standardized uptake value (SUV) in HCC lesions by the maximal SUV in noncancerous tissue, a lesion was calssified "+" by both visual assessment and a semi-quantitative target-background ratio(T/B)>1, "-" when its activity was less than or same as that in nontumor tissue and T/B≤1.Results1. The sensitivities of 18F-FDG, 11C-acetate PET/CT scan, CT enhancement scanning and MR enhancement scanning are 41.94%,80.65%,86.21% and 83.33%, specificities of which are 41.67%,33.33%,8.3% and 100%, accuracies are 41.86%,67.44%,63.41% and 85.7%, positive predictive values are 65%,75.76%,69.44% and 100%, negative predictive value are 21.74%,40%,20% and 50%. The mean lesion-to-liver SUV ratios of 11C-acetate and 18F-FDG is 1.52±0.53 and 1.50±1.12 respectively, no statistically significant difference is found.2. In six cases of hepatic cirrhosis nodules, five of them with increased 11C-acetate metabolism, three of them with slightly increased 18F-FDG metabolism, one case of hepatocyte fatty degeneration with increased 11C-acetate metabolism but no abnormal 18F-FDG metabolism, one case of inflammation change in liver with increased 18F-FDG metabolism but no abnormal 11C-acetate metabolism, one case of focal nodular hyperplasia shows normal 11C-acetate and 18F-FDG metabolism, one case of hepatic metastasis with increased 18F-FDG metabolism but no abnormal 11C-acetate metabolism, another case of two hepatic metastases with obviously increased 18F-FDG metabolism and circular slightly increased 11C-acetate metabolism in marginal parts.3. The sensitivities of 11C-acetate and 18F-FDG PET/CT scan in diagnosis ofⅠ-ⅡandⅡgrade HCC lesions are 69.23% and 30.77% respectively, when that in diagnosis ofⅢgrade HCC lesions are 66.67% and 100% respectively. No statistically significant difference is found in the 11C-acetate T/B ratios of HCC lesions in three groups with different histopathologic grade (p=0.739>0.05); statistically significant difference is found in the 18F-FDG T/B ratios of HCC lesions in three groups with different histopathologic grade (p=0.001<0.05)4. The sensitivities of 11C-acetate and 18F-FDG PET/CT scan in diagnosis of HCC lesions with largest diameter larger than 3cm are 87.5% and 68.75% respectively,the difference is not statistically significant (p=0.4497,>0.0500), but sensitivities of "C-acetate and 18 F-FDG PET/CT scan in diagnosis of HCC lesions with largest diameter≤3cm are 73.33% and 13.33% respectively, the difference is statistically significant (p=0.0265,<0.0500). No statistically significant difference is found in the 11C-acetate T/B ratios of HCC lesions in these two groups (p=0.144>0.05), but statistically significant difference is found in the 18F-FDG T/B ratios of HCC lesions in these two groups (p=0.001<0.05).5. Two cases of HCC with portal vein invasived show no abnormal 11C-acetate metabolism, one of them shows increased 18F-FDG metabolism,11C-acetate PET/CT scan can detect one intracavity metastasis in left upper abdominal part and two lung metastases in one patient after ectomy for liver cancer, when in another patient, after secondary liver implantation and treatment for multiple metastases have performed, 11C-acetate PET/CT scan can detect each one metastasis beside greater curvature of remnant stomach, left rectus abdominis, upper segment of descending colon and in the left adrenal gland region, three metastases in vesicorectal space, one lung metastasis; But only three metastases in vesicorectal space and one lung metastasis can be detected by 18F-FDG PET/CT scan.Conclusion1. The sensitivity of11C-acetate and CT enhancement scanning in diagnosis of HCC are higher than that of 18F-FDG.2. The sensitivity of 11C-acetate PET/CT scan in diagnosis of HCC (Ⅰ-ⅡandⅡgrade) are higher than that of 18F-FDG, but that of 18F-FDG in diagnosis of HCC (Ⅲgrade) are higher than 11C-acetate.3. The sensitivity of 11C-acetate in diagnosis of HCC lesions with largest diameter≤3cm are higher than that of 18F-FDG.4. 11C-acetate PET/CT scan can complement the insufficient of 18F-FDG PET/CT scan in diagnosis of well and moderately-differentiated HCC, but 18F-FDG can not be replaced by 11C-acetate, the relationship between 11C-acetate and 18F-FDG is complementary to each other.5. We should notice the false positive results of 11C-acetate, as some benign lesions, ie. hepatic cirrhosis nodules, hepatocyte fatty degeneration.