Clinical application of ¹¹C-methionine positron emission tomography for evaluation of pancreatic function

Introduction: In recent years, it has become increasingly necessary to evaluate pancreatic function after pancreatectomy, but few precise methods are available. Aims: To evaluate different surgical techniques for pancreatectomy in terms of the preservation of pancreatic function by ¹¹C-methionine positron emission tomography (PET), which determines amino acid metabolism in the pancreas. Methodology: The study included 33 pancreatectomy cases: 5 of distal pancreatectomy, 5 of pancreaticoduodenectomy, 10 of pylorus-preserving pancreaticoduodenectomy, 7 of duodenum-preserving pancreatic head resection, and 6 of inferior pancreatic head resection. The method was as follows. Approximately 370 MBq ¹¹C-methionine was intravenously injected. Crosssectional imaging of the pancreas was performed by PET after 30 minutes. The images obtained were used to determine the radioactivity concentration in the pancreas. By adjustment of the radioactivity concentration for body weight and dosage, the differential absorption ratio could be determined to indicate the level of accumulation in the pancreas. Each surgical method used was evaluated on the basis of the differential absorption ratio. Postoperative total pancreatic accumulation was divided by preoperative level to calculate the total preserved pancreatic function rate (TPPFR), and postoperative local pancreatic accumulation was divided by preoperative level to calculate the local preserved pancreatic function rate (LPPFR). These rates were then compared for the individual techniques used. Results: The results indicated that TPPFR and LPPFR were 61.2 ± 20.0% and 114.6 ± 29.4% for distal pancreatectomy (n = 5), 31.8 ± 20.0% and 58.7 ± 30.0% for pancreati-coduodenectomy (n = 5), 21.6 ± 14.7% and 58.4 ± 29.8% for pylorus-preserving pancreaticoduodenectomy (n = 10), 47.9 ± 35.5% and 67.7 ± 30.6% for duodenum-preserving pancreatic head resection (n = 7), and 48.1 ± 29.5% and 83.9 ± 30.5% for inferior pancreatic head resection (n = 6). TPPFR was highest in distal pancreatectomy cases. Among the pancreatic head resections, TPPFR was quite high for both inferior pancreatic head resection and duodenum-preserving pancreatic head resection. In contrast, TPPFR for pancreaticoduodenectomy and pylorus-preserving pancreaticoduodenectomy was quite low. LPPFR was highest for distal pancreatectomy and only slightly lower for inferior pancreatic head resection. In contrast, LPPFR was markedly lower for pancreaticoduodenectomy and pylorus-preserving pancreaticoduodenectomy. Conclusion: In conclusion, this method using ¹¹C-methionine PET is clearly useful for the evaluation of pancreatic function after pancreatectomy.