Quantification of beam size impact on intensity-modulated proton therapy with robust optimization in head and neck cancer-comparison with intensity-modulated radiation therapy.
We assessed the effect of beam size on plan robustness for intensity-modulated proton therapy (IMPT) of head and neck cancer (HNC) and compared the plan quality including robustness with that of intensity-modulated radiation therapy (IMRT). IMPT plans were generated for six HNC patients using six beam sizes (air-sigma 3-17 mm at isocenter for a 70-230 MeV) and two optimization methods for planning target volume-based non-robust optimization (NRO) and clinical target volume (CTV)-based robust optimization (RO). Worst-case dosimetric parameters and plan robustness for CTV and organs-at-risk (OARs) were assessed under different scenarios, assuming a ± 1-5 mm setup error and a ± 3% range error. Statistical comparisons of NRO-IMPT, RO-IMPT and IMRT plans were performed. In regard to CTV-D99%, RO-IMPT with smaller beam size was more robust than RO-IMPT with larger beam sizes, whereas NRO-IMPT showed the opposite (P < 0.05). There was no significant difference in the robustness of the CTV-D99% and CTV-D95% between RO-IMPT and IMRT. The worst-case CTV coverage of IMRT (±5 mm/3%) for all patients was 96.0% ± 1.4% (D99%) and 97.9% ± 0.3% (D95%). For four out of six patients, the worst-case CTV-D95% for RO-IMPT (±1-5 mm/3%) were higher than those for IMRT. Compared with IMRT, RO-IMPT with smaller beam sizes achieved lower worst-case doses to OARs. In HNC treatment, utilizing smaller beam sizes in RO-IMPT improves plan robustness compared to larger beam sizes, achieving comparable target robustness and lower worst-case OARs doses compared to IMRT.
Baba H
，Hotta K
，Takahashi R
，Motegi K
，Sugama Y
，Sakae T
，Tachibana H
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Exploring the dosimetric impact of systematic and random setup uncertainties in robust optimization of head and neck IMPT plans.
This study aims to compare the dosimetric impact of incorporating systematic and random setup uncertainties in the robust optimization of head and neck cancer (HNC) Intensity Modulated Proton Therapy (IMPT) plans.
Bilateral HNC patients (n = 10) previously treated with conventional photon therapy at our institution were included. Both systematic and random setup uncertainties were incorporated into the robust optimization process of IMPT planning. Dosimetric comparisons were made between plans optimized with systematic (IMPT-S) versus random (IMPT-R) setup uncertainties, assessing both the clinical target volume (CTVs) and organs at risk (OARs) across various dosimetric metrics. Both plans applied a fixed range uncertainty of ± 3 % and a maximum setup uncertainty of ± 3 mm.
Both IMPT-S and IMPT-R plans achieved similar target coverage, meeting robustness criteria for CTVs. On average, the D95% voxel-wise min to the high-risk CTV (CTV_HR) was slightly higher in IMPT-S plans by 1.78 ± 0.72 % compared to IMPT-R plans. However, IMPT-R plans provided better OAR sparing, which was evident in both nominal and voxel-wise maximum values. While random setup errors in robust optimization improved OAR sparing, the clinical impact may be minimal where OAR doses are already well below tolerance levels.
Both IMPT-S and IMPT-R techniques met the robustness criteria for CTVs in HNC IMPT planning. Incorporating random setup uncertainties in robust optimization improves OAR sparing compared to systematic setup uncertainties. Further research is needed to explore the broader applicability of random setup errors and to integrate random uncertainties in robustness evaluations for a more comprehensive assessment of treatment plans.
Rana S
，Padannayil NM
，Zeidan Y
，Pokharel S
，Richter S
，Kasper M
，Saeed H
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Margin and robustness settings for a library-of-plans IMPT strategy for locally advanced cervical cancer.
Objective.This study aims to determine a margin and robustness setting for treating locally advanced cervical cancer (LACC) with a library-of-plans (LoP) based online-adaptive intensity-modulated proton therapy (IMPT).Approach.We analyzed 13 LACC patients with delineated planning and weekly repeat CT scans (reCTs). For each patient, 120 IMPT treatments of 25 fractions were simulated with a LoPs approach. Six different robustness settings (2-7 mm set-up robustness (SR) plus 3% range robustness (RR)) were used to create those 120 IMPT plans. Each fraction was simulated with a weekly reCT, combined with the sampling of inter- and intrafraction treatment uncertainties. The fraction doses were accumulated to obtain a treatment dose to the target volumes, distinguishing between the low-risk clinical target volume (CTV-T-LR) and the elective CTV (CTV-E). If one of the two targets obtained an adequate coverage for more than 90% of the treatments, different anisotropic margins were sampled on top of the robustness setting to the other target to obtain the Pareto-optimal margin in terms of adequate coverage versus increase in target volume.Main results.The percentage of treatments that reach the dose criterionV42.75Gy> 95% for the CTV-T-LR was 22.3%, 28.5%, 51.2%, 73.1%, 85.3%, and 90.0% for 2, 3, 4, 5, 6, and 7 mm SR plus 3% RR and for the CTV-E, this percentage was 60.4%, 73.8%, 86.5%, 92.3%, 96.9%, and 98.5%. The Pareto-optimal margin combined with a 5 mm/3% robustness setting for the CTV-T-LR with an adequate coverage for >90% of the treatments was given by {0, 1, 0, 3, 3, 0} mm in the left, right, anterior, posterior, cranial, caudal direction.Significance.Our study evaluated combinations of robustness and anisotropic margin settings for IMPT for LACC. With 5 mm SR and 3% RR for CTV-E and CTV-T-LR plus a margin to the CTV-T-LR of {0, 1, 0, 3, 3, 0} mm in left, right, anterior, posterior, cranial, and caudal ensured an adequate coverage for >90% of the simulated IMPT treatments.
Kuipers SC
，Godart J
，Negenman EM
，Corbeau A
，Zolnay AG
，Deuzeman HH
，de Boer SM
，Nout RA
，Hoogeman MS
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A unified path seeking algorithm for IMRT and IMPT beam orientation optimization.
Objective. Fully automated beam orientation optimization (BOO) for intensity-modulated radiotherapy and intensity modulated proton therapy (IMPT) is gaining interest, since achieving optimal plan quality for an unknown number of fixed beam arrangements is tedious. Fast group sparsity-based optimization methods have been proposed to find the optimal orientation, but manual tuning is required to eliminate the exact number of beams from a large candidate set. Here, we introduce a fast, automated gradient descent-based path-seeking algorithm (PathGD), which performs fluence map optimization for sequentially added beams, to visualize the dosimetric benefit of one added field at a time.Approach. Several configurations of 2-4 proton and 5-15 photon beams were selected for three head-and-neck patients using PathGD, which was compared to group sparsity-regularized BOO solved with the fast iterative shrinkage-thresholding algorithm (GS-FISTA), and manually selected IMPT beams or one coplanar photon VMAT arc (MAN). Once beams were chosen, all plans were compared on computational efficiency, dosimetry, and for proton plans, robustness.Main results. With each added proton beam, Clinical Target Volume (CTV) and organs at risk (OAR) dosimetric cost improved on average across plans by [1.1%, 13.6%], and for photons, [0.6%, 2.0%]. Comparing algorithms, beam selection for PathGD was faster than GS-FISTA on average by 35%, and PathGD matched the CTV coverage of GS-FISTA plans while reducing OAR mean and maximum dose in all structures by an average of 13.6%. PathGD was able to improve CTV [Dmax, D95%] by [2.6%, 5.2%] and reduced worst-case [max, mean] dose in OARs by [11.1%, 13.1%].Significance. The benefit of a path-seeking algorithm is the beam-by-beam analysis of dosimetric cost. PathGD was shown to be most efficient and dosimetrically desirable amongst group sparsity and manual BOO methods, and highlights the sensitivity of beam addition for IMPT in particular.
Ramesh P
，Valdes G
，O'Connor D
，Sheng K
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ResearchGate
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