| Objective: Differentiation between pancreatic malignant tumors and benign pancreatic lesions is difficult. 18F-FDG PET/CT and PET/CT delayed imaging have an important value in the differential diagnosis and clinical stage of pancreatic cancer. So we evaluated the value of dual-phase imaging and four-phase imaging of pancreatic lesions in diagnosis and staging. Method: We used 18F-FDG PET/CT dual-phase imaging to evaluate suspicion pancreatic lesions in 108 patients. The SUVmax within the lesions for early-phase were determined at 1 hour, the SUVmax within the lesions for delayed-phase were determined at 2 hours after intravenous injection of FDG. We used 18F-FDG PET/CT four-phase imaging to evaluate 42 of 108 patients based on dual-phase imaging. The SUVmax within the lesions for early-phase were determined at 1 hour. The SUVmax within the lesions for delayed-phase were determined at 2 hours, 4 hours and 6 hours after intravenous injection of FDG. The patients of dual-phase and four-phase imaging were classified as malignant and benign group, were calculated sensitivity, specificity, accuracy about diagnosis. We observed difference about the both imaging and the change of four-phase imaging on SUVmax, analysis the difference in clinical staging of pancreatic cancer using 18F-FDG PET/CT and CSI. Results: 1. The mean and range of SUVmax for Pancreatic lesions in dual-phase imaging and four-phase imaging. There was 26 patients in benign group of dual-phase imaging, the mean and range of SUVmax were(4.83±4.68)(1.7~19.7) at 1 hour,(5.73±5.76)(1.3~23.3) at 2 hour. There was 82 patients in malignant group of dual-phase imaging, the mean and range of SUVmax were(6.31±3.19)(2.4~19.6) at 1 hour,(8.13±4.29)(2.5~29.2) at 2 hour. Differentiation between malignant and benign groups is difficult by 18F-FDG PET/CT dual-phase imaging due to considerable overlapping between the SUVmax values of the two group diseases. The mean and range about RI(retention index) between malignant and benign groups in dual-phase imaging were(14.93±18.85)(-3.53~45.83)、(28.65±15.01)(1.96~76). The difference is statistically significant(t=3.656,P=0.000). There was 10 patients in benign group of four-phase imaging, the mean and range of SUVmax were(4.69±3.91)(1.7~13.10) at 1 hour,(5.91±5.55)(1.7~17.10) at 2 hour,(5.90±5.88)(1.7~18.50) at 4 hour,(5.82±5.89)(1.7~19.90) at 6 hour. There was 32 patients in malignant group of four-phase imaging, the mean and range of SUVmax were(5.69±1.98)(2.4~10.30) at 1 hour,(7.15±2.67)(2.5~12.7) at 2 hour,(8.20±3.06)(3.5~14.60) at 4 hour,(7.98±3.36)(2.9~15.00) at 6 hour. The SUVmax reaches maximum value at 4 hour imaging in most pancreatic malignant tumors and at 2 hour imaging in most pancreatic benign tumors. RI4 is more valuable than RI2 in differential diagnosis, the main reason is mass-forming pancreatitis which lead to false positive. 2. The sensitivity, specificity, accuracy of dual-phase and four-phase 18F-FDG PET/CT imaging. In dual-phase imaging, take RI>10% as threshold, the sensitivity, specificity, accuracy of diagnosis were 90.2%, 34.7% and 78.1% respectively. When combining the SUVmax>2.5 at 1hour and RI>10% as threshold, the sensitivity, specificity, accuracy of diagnosis were 87.8%, 56.5% and 80.9% respectively. When combining the SUVmax>3.0 at 1 hour and RI>10% as threshold, the sensitivity, specificity, accuracy of diagnosis were 84.1%, 69.5% and 81.0% respectively. We get higher sensitivity, specificity, accuracy of diagnosis were 84.1%, 69.5% and 81.0% respectively when combine the SUVmax>3.0 at 1 hour and RI>10% as threshold. Take RI2>10% as threshold, the sensitivity, specificity, accuracy of diagnosis in four-phase imaging were 87.5%, 30% and 73.8% respectively. Take RI4>10% as threshold, the sensitivity, specificity, accuracy of diagnosis were 96.8%, 50.0% and 85.7% respectively. When combining the SUVmax>2.5 at 1 hour and RI2>10% as threshold, the sensitivity, specificity, accuracy of diagnosis were 87.5%, 60.0% and 81.0% respectively. When combining the SUVmax>2.5 at 1 hour and RI4>10% as threshold, the sensitivity, specificity, accuracy of diagnosis were 93.7%, 60.0% and 85.7% respectively. When combining the SUVmax>3.0 at 1hour and RI2>10% as threshold, the sensitivity, specificity, accuracy of diagnosis were 84.3%, 60.0% and 78.6% respectively. When combining the SUVmax>3.0 at 1 hour and RI4>10% as threshold, the sensitivity, specificity, accuracy of diagnosis were 90.6%, 60.0% and 83.3% respectively. We get higher sensitivity, specificity, accuracy of diagnosis were 93.7%, 60.0% and 85.7% respectively when combine the SUVmax>2.5 at 1 hour and RI4>10% as threshold. 3. The finding of metastatic lesions in dual-phase and four-phase 18F-FDG PET/CT imaging. 5 occult liver metastases were detected at 18F-FDG PET/CT, 3 liver metastases in 5 were unclear at 1 hour. PET/CT delayed imaging can find and confirm more liver metastases. The SUVmax reaches maximum value at 4hour imaging in most liver and lymph node metastases. 4. The value of dual-phase imaging comparing with CSI in clinical staging of pancreatic cancer. Clinical staging in 19 patients was raised by PET/CT. 18F-FDG PET/CT and PET/CT delayed imaging findings influenced the clinical management of 22 patients, 5 with liver metastases, 4 with lymph node metastases, 1 with lung metastases and 2 with second tumor. PET/CT completely changed the diagnosis direction of CSI in10 patients. Conclusions: 1. 18F-FDG PET/CT Delayed imaging has important value in the differential diagnosis of pancreatic lesions. The different peak time point uptake FDG between pancreatic benign and malignant lesions can be used as a new clue in the differential diagnosis. 2. Combining the SUVmax and RI can improve the accuracy of diagnosis, the RI4 was much valuable than RI2. 3. PET/CT has important value in the clinical staging of pancreatic cancer, delayed imaging contributes to find more metastasis. |
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