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F18-FDG PET has been shown to be helpful for the diagnosis of primary, recurrent, and metastatic lesions in a variety of tumours. However, problems exist in the diagnosis of tumours with low metabolism, such as prostate cancers, low-grade sarcomas, low-grade lymphomas and well-differentiated hepatocellular carcinomas. With the limitation of F18-FDG, other PET tracers such as C11-Acetate may have a role to play for the detection of some of these tumours, in particular, prostate cancers and hepatocellular carcinomas.
The exact uptake mechanism of 11C-acetate is not known, but studies suggest that it is incorporated into the lipid pool in cancer tissue with low oxidative metabolism and high lipid synthesis.
In studies involving small groups of patients with prostate cancers, C-11 Acetate was found to have a higher sensitivity than FDG-PET for the detection of primary tumour within the prostate gland, nodal metastases and bone metastases as well as the detection of recurrent disease. F18 NaF PET bone scans are also noted to have a higher sensitivity than conventional TC99m MDP bone scans for the detection of bone metastases. Hence, there may be a possible role of using a dual-PET isotope approach of F18 NaF and C11-Acetate for the imaging of prostate cancer.
In the case of hepatocellular carcinoma (HCC), studies have shown that the poorly differentiated HCCs were detected by 18F-FDG and the well-differentiated types were detected by 11C-acetate. The use of F18-FDG alone would result in false negative findings in the presence of well differentiated HCC. Therefore, a dual-isotope PET protocol of using 18F-FDG and 11C-acetate as radiopharmaceuticals would be more useful than F18-FDG alone for the evaluation of indeterminate hepatic lesions and would have a higher sensitivity and accuracy for the detection and staging of HCCs and for pre-transplant evaluation.
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