In this paper, a method for dose calculation with pencil beam kernels constructed by point kernel superposition was proposed to accelerate the dose calculation during intensity optimization iteration. With this method, the direct aperture optimization method can be integrated in the planning system based on point kernel convolution/superposition model. The dose calculation time was also reduced during the iteration. From the result of the phantom and clinical patient data test, it was concluded that this method could be used for the intensity optimization of iteration dose calculation as the satisfied precision due to the optimization result coherence obtained. By implementing the method in the planning system product based on point kernel convolution/superposition model, a lot of additional research and development works for the pencil beam dose calculation model as well as the product maintenance cost can be avoided.
ObjectiveTo analyze the risk factors for pancreatic fistula following pancreaticoduodenectomy. MethodThe clinical data of 150 patients underwent pancreaticoduodenectomy in this hospital from January 2011 to January 2014 were reviewed, and the potential factors for pancreatic fistular were evaluated by both univariate and multivariate analysis. ResultsThe incidence of pancreatic fistula was 12.7% (19/150). Univariate analysis results showed that the age, preoperative high bilirubin level, texture of the remnant pancreas, diameter of wirsung, operative time were associated with pancreatic fistula following pancreaticoduodenectomy (P < 0.05). Multivariate logistic regression analysis results revealed that the texture of the remnant pancreas, diameter of wirsung, and operative time were the inde-pendent risk factors (P < 0.05) for pancreatic fistula following pancreaticoduodenectomy. ConclusionsTexture of the remnant pancreas, diameter of wirsung, operative time are independent risk factors for pancreatic fistula following pancreaticoduodenectomy. Rich experience and skilled surgical procedures could effectively reduce the incidence of pancreatic fistula.