| Objective:To investigate the factors which affects the passing rate of intensity-modulated radiotherapy(IMRT)plans.Methods:A totoal of 68 static IMRT plans designed on Pinnacle treatment planning systems were selected.The related parameters including monitor unit(MU),number of beams(NB),number of segments(NS),area of segments(AS)of plans were extacted and analyzed according to various sites,among which the average value(MAS)and the coefficient of variation of segment area(CVA)were calculated.All fields were normalized to gantry angle 0° and the dose distributions were measured with PTW seven29 chamber array and solid water phantom based on Elekta Synergy accelerator.Then PTW VeriSoft software was used to compare the differences between measured results and computed values.Using 3mm/3%criteria,the Gamma passing rates of Local and Max were analyzed and compared.Analysis of variance was perfomed for the passing rate of Local among various sites.The correlations between MU,NS,MAS,CVA and the passing rate of Local were analyzed.Multiple linear regression method was used to obtain the linear relationship between the passing rate and the affecting factors.Results:The passing rates of Local were lower than those of Max in all sites(P<0.01).The passing rates of Local were lower than those of Max for all plans(P<0.01).The analysis of variance showed that the passing rates of Local were different among various sites(F=7.695,P<0.001).Dunnett-t test showed that the passing rates in the sites of brain,thorax,abdomen and pelvis were different from that of head and neck(P<0.02).There was a negative correlation between the passing rate of Local and MU,NS,CVA,respectively(P<0.01).Multiple linear regression model showed that there was a linear relationship between the passing rates of Local and treatment sites,NS and CVA.Conclusions:The passing rate of Local is significantly lower than that of Max.Compared with plans for other sites,head and neck plan has a lower passing rate.The passing rates of Local can be preliminary estimated by monitor unit and the number of segment.Treatment site,the number of segments,the coefficient of variation of segments area are the main factors that affect the passing rates of Local.Multiple linear regression equations can provide some guidance for the design and selection of optimal plans.Objective:To explore the application of Auto-Planning(AP)tool of Pinnacle3 treatment planning system in gynecological cancer intensity-modulated radiation therapy(IMRT).Methods:Ten clinically delivered gynecological treatment plans optimized by AP engine were selected.Plans were changed by modifying parameter settings and reoptimized with the AP tool.Dosimetric differences were compared.There were several comparisons,IMRT and simplified intensity modulated radiotherapy(sIMRT),pure dose volume constrains(DV)and dose volume combined with mean dose constrains using biological optimization(DV&MD),three different tuning balance(P11%,PO%,P100%)in advanced settings,using cold-spot ROIs or not in advanced settings.The differences of homogeneity index(HI),conformity index(CI),dose for OARs and monitor units(MUs)were compared by paired samples T test.Results:Compared with IMRT plans,sIMRT had a worse CI and HI(CI:0.86 vs 0.85,HI:0.08 vs 0.09),while the dose in OARs was similar or slightly higher.The highest increase of average dose was in right femoral head(29.13Gy vs 29.83Gy).MUs decreased by 8.5%(670 vs 604).Compared with DV plans,DV&MD had a worse CI and HI(CI:0.86 vs 0.85,HI:0.08 vs 0.10)while the dose of other OARs were similar or decreased(Rectum Dmean:43.36Gy vs 38.69Gy,Bone marrow Dmean:32.50Gy vs 31.07Gy)except that of small intestine with V52(0.O1cm3 vs 0.21cm3).MUs incresed by 8.6%(670 vs716).Compared with P11%plans,P0%had a lower HI(0.10 vs 0.09),while the dose in OARs was similar or slightly higher.The highest increase of average dose was in bone marrow(31.07Gy vs 31.77Gy).Compared with P11%plans,P100%had a worse CI(0.85 vs 0.83),while the dose in OARs was similar or slightly higher(Rectum Dmean:38.69Gy vs 38.38Gy,small intestine V50:22.16 cm3 vs 24.33 cm 3).Compared with P0%plans,P100%had a worse CI and HI(CI:0.85 vs 0.83,HI:0.09 vs 0.10),while the dose in OARs was similar or lower(Right femoral head Dmean:29.20Gy vs 27.46Gy,Bone marrow Dmean:31.77Gy vs 30.58Gy).There were no statistically significant differences among P11%?P0%?P100%in MUs.Compared with plans using cold-spot ROIs,V95 and V100 were all lower in plans without using cold-spot ROIs while CI decreased and HI increased(CI:0.86 vs 0.84,HI:0.08 vs 0.09).The dose of OARs was similar or decreased(Bone marrow Dmean:32.5Gy vs 32.3Gy)except that of small intestine with V50(16.98cm3 vs 21.84cm3).Conclusions:For gynecological cancer plans optimized by AP engine,sIMRT may be a good choice while taking treatment efficiency and delivery into account.If the requirement of target uniformity can be relaxed,dose volume combined with mean dose constrains using biological optimization can effectively reduce the dose in OARs.P0%plans have a best uniformity while P100%have a worst conformity.Dose in OARs is not always decreasing by adjusting tuning balance from 11%to 100%,Using cold-spot ROIs is recommended while considering more about dose distributions of target. |
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