Impact of Conformality function in Monaco planning system on volume-modulated arc therapy plan for cervical cancer
Objective To explore the impaction of different parameter values of Conformality function on the quality of Mona-co planning system.Methods A total of 15 patients with cervical cancer were enrolled,which aged 46-74 years old with mean age of 51 years old.The volume-modulated arc therapy(VMAT)plan was designed without the function or with param-eters of the Conformality function of 0.25,0.50,0.75,1.00,respectively,and non-function plans were used to evaluate dosimet ric parameters of target area,organs at risk(OAR),volume and plan execution efficiency of 20 Gy,30 Gy and 40 Gy isodose lines.Results There were statistically significant differences of target dosimetry among different function parameter plans(P＜0.05).When the Conformality function parameter value was 0.25,the increase and decrease of Dmax,Dmin,Dmean and non-function in target area were 2.45％,-0.96％and 1.48％,respectively;the conformity index(CI)and homogeneity index(HI)increased 0.05 and 0.04,respectively.When Conformality function parameter value was＞0.50,there was no significant change in CI and HI,and no significant difference in dosimetry between small intestine,colon,left and right femoral head(P＞0.05).When the parameter value was 0.25,rectum V30,V40[(81.80±7.74)％,(63.44±10.23)％],bladder V30,V40[(78.82±5.69)％,(56.40±9.33)％],normal tissue V20,V30,V40[(6 137.64±622.88)cm3,(2 903.55±221.08)cm3,(1 862.93±112.81)cm3]showed the lowest.There were sta tistically significant differences in V30 and V40 of bladder and rectum among different parameters(P＜0.05).With the increase of Conformality function parameteer value,the machine parameter value decreased,and the differences of machine unit(MU),number of control point(CP)and delivery time(DT)in each function parameter value were statistically significant(P＜0.05).Conclusion It is demonstrated that the proper use of Conformality function design in cervical cancer Monaco planning system can improve the plan quality,and the parameter value is appropriate to set between 0.25 and 0.75,and 0.50 is recommended for clinic with comprehensive dosimetric parameters and plan execution efficiency.
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