PURPOSETo validate that DMPO model for "one step" algorithm can reduce the total MLC segments number, we compare the dosage distribution of "one-step" algorithm with "two-step" algorithm for generating IMRT MLC segments.

METHODSOn the platform of "Pinnacle 8.0h" version radiation treatment planning system developed by Philips, we respectively select one head and neck tumor case, one thorax tumor case and one abdomen tumor case, by means of designing seven fields IMRT planning, then utilized "one-step" algorithm and "two-step" algorithm to optimize and generate IMRT MLC segments, and then calculated dosage distribution, evaluated dosage distribution lines and DVH diagram, in order to compare the two MLC segment groups generated by the two different algorithm.

RESULTFor the three IMRT plans selected by us, the number of MLC segments generated by "two-step" algorithm appear to be larger than "one-step" algorithm but dosage distribution seems to be worse than the latter.

DISCUSSIONFor utilizing the "Pinnacle" plan system to design IMRT plan, "one-step" algorithm with "DMPO" definitely can effectively reduce the number of MLC segments, what's more, the result of dosage distribution seems to be better.

Algorithms ; Radiotherapy Dosage ; Radiotherapy, Intensity-Modulated ; methods

Chronic pancreatitis is a focal or diffuse chronic inflammation and fibrosis of pancreatic tissue, which is progressive, persistent and irreversible.Chronic pancreatitis in children has its own characteristics of early onset and frequent occurrence, which greatly affects the nutritional status and quality of life of children.Recently, diagnosis and treatment of this severe inflammation gradually improved with a burgeoning technique: endoscopic retrograde cholangiopancreatography (ERCP), especially in the treatment of pediatric chronic pancreatitis.The detection rate of the disease has been increasing year by year.As an effective and safe procedure for the treatment of chronic pancreatitis in children, ERCP has replaced traditional surgery and become the first-line treatment method for pediatric chronic pancreatitis.

To investigate the in situ intestinal absorption characteristics and pharmacokinetic behavior of metformin-resveratrol compound water-in-oil nanoemulsion (MRCE) in rats, the in situ intestinal perfusion model was constructed in rats to study the intestinal absorption characteristics of MRCE in different intestinal segments. Male Sprague-Dawley rats were randomly divided into two groups. After intragastric administration of metformin and MRCE, blood was taken at a preset time point. The content of metformin in intestinal perfusion samples and blood samples at various time points was determined by HPLC. Plasma concentration-time profiles of free metformin and MRCE were calculated, and the main pharmacokinetic data were processed and analyzed by DAS 2.1.1 software. The absorption rate constant (Ka), the effective permeability (Peff) and the percentage of absorption (PA) of MRCE in each intestinal segment were significantly higher than those of metformin (P < 0.05). The area under the drug-time curve (AUC0-72 h), the half-life (t1/2) and mean residence time (MRT0-72 h) of MRCE were 1.68, 11.25 and 6.97 times of metformin, respectively (P < 0.01).The relative bioavailability of MRCE was 167.6%. The 90% confidence interval of AUC0-72 h was 156.9%-187.4%, which was not within the standard interval of bioequivalence. The intestinal absorption of MRCE was significantly better than that of free metformin; MRCE improved the oral bioavailability of metformin and was not bioequivalent to metformin.