Room: AAPM ePoster Library
Purpose: Dose-volume is the most commonly used optimization parameter in inverse intensity modulation plan.It is the purpose of the research to seek better optimization parameters in IMRT inverse planning optimization.
Methods: The inverse intensity modulation plans of 20 patients with left breast cancer were analyzed retrospectively,the RTplan,RTdose,RTstructures and CT images were imported into the PlanIQ.PlanIQ offers a tool called Feasibility DVH which quantitatively determines regions of a DVH that are impossible,difficult,and probable on a per OAR basis,based on an ideal dose falloff from the prescription dose at the target boundary.We used the predicted DVH curve to establish the ideal OAR (heart,left lung) curve for each patient.Extracted 9 curves of Ideal DVH for each OAR with the feasibility range is from 0.01(impossible) to 0.1(difficult),and calculated a set of dose-volume parameters corresponding to each curve.The 9 sets of parameters were re-optimized as the optimization parameters,and the re-optimization order was successively decreased according to the degree of difficulty(ie,Feasibility ranging from 0.01 to 0.1).Multiple linear regression analysis was performed between the 9 inverse intensity modulation plans generated by each patient re-optimization.
Results: The plans of re-optimization of 20 patients with left breast cancer were compared with the original plan. Under the premise that there was no statistical difference in PTV:1.Heart,the dose-volume optimization parameter corresponding to the re-optimization plan feasibility value at 0.63±0.06 yielded the lowest dose; 2.Left-lung,the re-optimization plan with a feasibility of 0.59±0.07,the corresponding dose-volume optimization parameter produced the lowest dose. When considering OARs(heart and left-lung) and PTV, the dose-volume parameters corresponding to the feasibility range of 0.05-0.07 produced the best planned quality.
Conclusion: Feasibility range of 0.05-0.07 produced the best planned quality in left breast cancer reverse intensity modulation planning. Better and personalized optimal parameters can be obtained by ideal DVH,so as to produce a better quality treatment plans.