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margin from CTV to PTV.
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Objective To study the application of correlation statistical analysis model in IMRT planning optimization. Methods A correlation statistical analysis model was established. IMRT plans of 5 prostate cancer patients were randomly chosen from the ADAC Pinacal 7.6 version planning system. The beam parameters, objective functions of the target area and optimization parameters of the primary plan were kept unchanged. The main optimization parameters including EUD parameter a,weight (w) and EUD_(max) of OAR were adjusted in optimization procedure successively. The correlation analysis (CF) and optimization efficiency analysis (OF) were carried out on the results of the optimization. The optimal value of parameters (MORt{}) with the best dose distribution was obtained and substituted in the corresponding primary plan.After optimization, the dose distributions of the two IMRT plans were compared. Results There were signif-icant differences with different optimization methods. The EUD parameter a and weight factor (w) almost had no effect on volume dose of OAR (OF < 0.01), though had obvious effect on the maximum dose and mean dose (OF≈1). The CF analysis showed that the correlation between the PTV ( V_(95)) volume and OAR dose was different when the EUD parameter a and w were applied for optimization. Meanwhile, the difference was proportional to the distance between the target area and OAR. The mean dose of OAR was decreased and the mean dose of PTV was more close to the prescription dose when the optimization parameters of the prima-ry plan were substituted with MOR{a} ,MOR{w} and MORt{EUD_(max)}. Besides, the DVH and isedose dis-tribution of the secondary plan were better. Conclusions The correlation statistical analysis model can be used to accurately determine the scope of optimization parameters in the IMRT planning procedure in prostate cancer, and an IMRT plan which fulfils the clinical requirement can be obtained efficiently.
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Objective To study if the dose verification technique for three dimensional conformal radiation therapy ( 3 DCRT) can be applied for simplified intensity modulation radiation therapy ( sIM RT). Methods From 1988 patients treated by sIMRT in our department,12 were chosen randomly for the study. For each case,3 differert plans of 3DCRT,sIMRT,and IMRT were worked out with Pinnacle TPS,and the dose verification for each plan was carried out with Elekta Precise LA by using 2D diode-matrix of MapCHECK Model 1175. Results For slMRT,the overall average percentages of pass points for DD(DTA) 2% (2 mm) ,3% (3 mm)and 4% (4 mm) were 90.5% ,94.8% and 98.2% reapectively,which were slightly worse when comparing with those of 3DCRT with deterioration of 1.9% (t=2.19,P=0.040) ,1.0% (t= 1.52,P=0.144) and 0.2% (t=0.05,P=0.623), but slightly better comparing with those of IMRT with increment of 2.1% (t=2.17,P=0.041) ,1.5% (t=2.62,P=0.016) and 1.5% (t=3.68,P=0.001) for 2% (2 mm) ,3% (3 mm) and 4% (4 mm) ,respectively. Conclusions The sIMRT technique simplifies the complicated dose verification procedure of I MRT. When the sIMRT technique is formally used, the procedure of dose distribution verification for 3DCRT can be used directly for slMRT.
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This paper introduces the basic principle,structure and technique characteristics of MM50 raceway electron cyclotron.Its clinical application to radiotherapy is discussed.