ABSTRACT
Objective:To improve the accuracy of cone-beam CT (CBCT) image registration by using a dose-guided registration algorithm based on multi-objective optimization.Methods:A total of 28 sets of CBCT images of 6 patients with lung cancer and 5 patients with cervical cancer admitted to Harbin Medical University Cancer Hospital in 2022 were retrospectively analyzed. Using the results of bone-based registration as the starting points for dose registration algorithm, the dose fluence weighted mean square errors of each displacement point in surrounding three-dimensional space were calculated, and the candidate displacement points were selected by unsupervised k-means clustering method. The three-dimensional dose distribution of each candidate displacement point was calculated by using the limited size pencil beam algorithm, and the dose histogram indexes were extracted as the optimization variables of the multi-objective optimization algorithm. After the Pareto optimal solution set obtained using multi-objective genetic algorithm, the optimal unique solution was then determined based on the predetermined objective weight scheme.Results:After dose optimization registration, the values of D 90%, D 95%, D 98%, D mean and conformity index (CI) of planning target volume (PTV) of lung cancer patients were increased by 0.23 Gy, 0.49 Gy, 1.05 Gy, 0.15 Gy, 0.03 compared with conventional registration, respectively, and no significant difference was found for the organs at risk (OAR). For cervical cancer cases, the values of D 90%, D 95%, D 98%, D mean and CI of PTV were increased by 0.72 Gy, 1.15 Gy, 2.53 Gy, 0.24 Gy, 0.05 compared with conventional registration, respectively, whereas the evaluation indexes of partial OAR were decreased by 1.06-1.81 Gy. Conclusion:The proposed dose-guided registration algorithm can improve the dose coverage for the target area, decrease the dose for OAR and reduce residual error of rigid registration algorithm, which can be implemented as part of online adaptive radiotherapy.
ABSTRACT
Objective We aimed to explore the difference of dosimetry among intensity modulated radia-tion therapy(IMRT),volumetric modulated arc therapy(VMAT)and helical tomotherapy(TOMO)in the radio-therapy of medulloblastoma.Methods Ten children's patients with the medulloblastoma were selected and de-signed in this study.A clinically feasible radiotherapy plan was designed for IMRT(5 fields),VMAT and TOMO. Conformality index(CI),homogeneity index(HI),V107,maximum dose(Dmax),organ at risk(OAR)dose-volume level,monitor units and treatment time were used to analyze in these groups.Results CI,HI,V107,Dmaxand OAR of target areas were significantly superior to VMAT and IMRT in the TOMO group of target PTV for whole brain full radiotherapy.The organ at risk dose-volume level in the TOMO group was lower than that in VMAT and IM-RT(5 fields)groups(P<0.05).The TOMO group also had the most monitor units and the longest treatment time (P<0.05).Hence,the patients in the TOMO group could irradiate completely the whole brain and full spinal cord without moving treatment couch to avoid the error from the man-made movement in VMAT and IMRT(5 fields)treatments.Conclusion In the radiotherapy of medulloblastoma,the dose distribution of patients in the TOMO group are superior to the VMAT and IMRT groups(5 fields).However,the number of monitor units and treatment time is significantly increased during treatment,and its clinical effect needed to be further studies.
ABSTRACT
Objective We aimed to explore the difference of dosimetry among intensity modulated radia-tion therapy(IMRT),volumetric modulated arc therapy(VMAT)and helical tomotherapy(TOMO)in the radio-therapy of medulloblastoma.Methods Ten children's patients with the medulloblastoma were selected and de-signed in this study.A clinically feasible radiotherapy plan was designed for IMRT(5 fields),VMAT and TOMO. Conformality index(CI),homogeneity index(HI),V107,maximum dose(Dmax),organ at risk(OAR)dose-volume level,monitor units and treatment time were used to analyze in these groups.Results CI,HI,V107,Dmaxand OAR of target areas were significantly superior to VMAT and IMRT in the TOMO group of target PTV for whole brain full radiotherapy.The organ at risk dose-volume level in the TOMO group was lower than that in VMAT and IM-RT(5 fields)groups(P<0.05).The TOMO group also had the most monitor units and the longest treatment time (P<0.05).Hence,the patients in the TOMO group could irradiate completely the whole brain and full spinal cord without moving treatment couch to avoid the error from the man-made movement in VMAT and IMRT(5 fields)treatments.Conclusion In the radiotherapy of medulloblastoma,the dose distribution of patients in the TOMO group are superior to the VMAT and IMRT groups(5 fields).However,the number of monitor units and treatment time is significantly increased during treatment,and its clinical effect needed to be further studies.