RESUMO
Objective:To evaluate the automatic optimization performance and clinical feasibility of the intelligent optimization engine (IOE) in the Ethos online adaptive radiotherapy platform.Methods:Clinical data of 11 patients with postoperative cervical cancer treated with Halcyon accelerator were retrospectively analyzed. Manual planning was performed for all patients using the 4 full arc volumetric modulated arc therapy (VMAT) (Manual-4Arc) in Eclipse, with a prescription dose of 45 Gy/25F. Patient images and structures were imported into the Ethos simulator, and appropriate clinical goals were added based on clinical requirements. The target coverage was normalized to 95%. Automatic plan generation was conducted using IOE, resulting in 7, 9, and 12 field intensity modulated radiotherapy (IMRT) plans (IMRT-7F、IMRT-9F、IMRT-12F), as well as 2 and 3 arc VMAT plans (VMAT-2Arc、VMAT-3Arc). Dosimetric index comparisons were made between the Manual-4Arc plans and the 5 groups of IOE-generated plans through one-way analysis of variance. Based on the analysis results, Turky post hoc multiple comparisons were performed to evaluate the automatic optimization performance of IOE.Results:In terms of the high dose area, the IMRT-12F plans showed the lowest D 1% for the planning target volume (PTV), and there were significant differences compared to the Manual-4Arc plans ( P=0.004). Regarding target coverage, all groups produced clinical target volume (CTV) plans that met the clinical requirements. Although the Ethos online adaptive plans were normalized during planning, the PTV coverage was slightly insufficient. For organs at risk (OAR) close to the target, such as the bladder, there were significant differences in V 30 Gy, V 40 Gy, and D mean among the 6 groups of plans. The dose ranking for the bladder was generally as follows: IMRT-12F<IMRT-9F<Manual-4Arc<IMRT-7F<VMAT-3Arc<VMAT-2Arc. There were significant statistical differences in V 30 Gy and D mean for the rectum, and the dose ranking was generally consistent with that of the bladder, except for a switch between the IMRT-7F and Manual-4Arc plans. There were no significant differences in rectal V 40 Gy, small intestine D max, and D mean among the 6 groups of plans. For OAR distant from the target, such as the left and right femoral heads, spinal cord, and bone marrow, the dose ranking was generally as follows: IMRT-12F<IMRT-9F<IMRT-7F<VMAT-2Arc<VMAT-3Arc<Manual-4Arc. Conclusion:The plans automatically generated by Ethos IOE in postoperative patients with cervical cancer can achieve similar performance to manual plans, and the automatically generated IMRT-12F and IMRT-9F plans are recommended for clinical use.
RESUMO
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.