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Yang J, Liu G, Liu HY, Nie X, Yang ZY, Han J, Zhang S, Liang ZW. Influence of CyberKnife Prescription Isodose Line on the Discrepancy of Dose Results Calculated by the Ray Tracing and Monte Carlo Algorithms for Head and Lung Plans: A Phantom Study. Curr Med Sci 2020; 40:301-306. [PMID: 32337689 DOI: 10.1007/s11596-020-2177-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 03/24/2020] [Indexed: 11/29/2022]
Abstract
Incorporation of the Monte Carlo (MC) algorithm in optimizing CyberKnife (CK) plans is cumbersome, and early models unconfgured MC calculations, therefore, this study investigated algorithm-based dose calculation discrepancies by selecting different prescription isodose lines (PIDLs) in head and lung CK plans. CK plans were based on anthropomorphic phantoms. Four shells were set at 2-60 mm from the target, and the constraint doses were adjusted according to the design strategy. After optimization, 30%-90% PIDL plans were generated by ray tracing (RT). In the evaluation module, CK plans were recalculated using the MC algorithm. Therefore, the dosimetric parameters of different PIDL plans based on the RT and MC algorithms were obtained and analyzed. The discrepancies (mean±SD) were 3.72%±0.31%, 3.40%±0.11%, 3.47%±0.32%, 0.17%±0.11%, 0.64%±3.60%, 7.73%±1.60%, 14.62%±3.21% and 10.10%±1.57% for D1%, D(mean), D98% and coverage of the PTV, DGI, V5, V3 and V1 in the head plans and -6.32%±1.15%, -13.46%±0.98%, -20.63%±2.25%, -34.78%±25.03%, 122.48%±175.60%, -12.92%±5.41%, 3.19%±4.67% and 7.13%±1.56% in the lung plans, respectively. The following parameters were signifcantly correlated with PIDL: dD98% at the 0.05 level and dDGI, dV5 and dV3 at the 0.01 level for the head plans; dD98% at the 0.05 level and dD1%, dD(mean), dCoverage, dDGI, dV5 and dV3 at the 0.01 level for the lung plans. RT may be used to calculate the dose in CK head plans, but when the dose of organs at risk is close to the limit, it is necessary to refer to the MC results or to further optimize the CK plan to reduce the dose. For lung plans, the MC algorithm is recommended. For early models without the MC algorithm, a lower PIDL plan is recommended; otherwise, a large PIDL plan risks serious underdosage in the target area.
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Affiliation(s)
- Jing Yang
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023, China
| | - Gang Liu
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023, China
| | - Hong-Yuan Liu
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023, China
| | - Xin Nie
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023, China
| | - Zhi-Yong Yang
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023, China
| | - Jun Han
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023, China
| | - Sheng Zhang
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023, China
| | - Zhi-Wen Liang
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023, China.
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Wang D, DeNittis A, Hu Y. Strategies to optimize stereotactic radiosurgery plans for brain tumors with volumetric-modulated arc therapy. J Appl Clin Med Phys 2020; 21:45-51. [PMID: 32043810 PMCID: PMC7075387 DOI: 10.1002/acm2.12818] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 11/20/2019] [Accepted: 12/17/2019] [Indexed: 12/15/2022] Open
Abstract
Purpose Prescription practice in SRS plans for brain tumors differs significantly for different modalities. In this retrospective study, the strategies to optimize SRS plans for brain tumors with volumetric arc therapy (VMAT) were presented. Methods Fifty clinically treated cases were stratified by the maximum target size into two groups (≥ 2 cm in 25 cases and <2 cm but ≥1 cm in 25 cases), which were optimized using traditional LINAC MLC‐based approaches with the average prescription isodose line (P‐IDL) of (91.4 ± 0.6)%. Four to five plans have been created for each case with variation of the P‐IDL from 65% to 90%. The optimization strategies to select an optimal P‐IDL, to use tuning structures within the target and beyond as well as to use NTO (normal tissue objectives), were applied to all new plans. Results The optimal P‐IDL was found to be around 75%. After applying the new optimization strategies with an average P‐IDL of 74.8%, the mean modified gradient index (mGI) and V12 were reduced by 25% and 35%, respectively for both groups. The Paddick conformity index (PCI) was averagely improved by 8%. The average homogeneity index (HI) and focal index (FI) were increased by 22% and 50%, respectively. The mGI was inversely proportional to the PTV volumes. The shape of the dose distribution in target was also changed from concave to convex. The comparison of PCI with historical data from other institutes and modalities shows that the plans in this study have the best conformity near the target. Conclusions With the new optimization strategies for VMAT SRS plan of brain tumor more conformal plans in both high and intermediate dose region (~50% of the PD) were created, in which the dose in the core of the target was notably increased while V12 and mGI were significantly decreased, and PCI was improved. The mGI was inversely proportional to the PTV volumes. The optimal P‐IDL is around 75%. The average PCI is the best in this study compared with the published historical data. These strategies are applicable to treatment planning for multiple brain and liver tumors where sparing the tissue peripheral to the target is critical.
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Affiliation(s)
- David Wang
- Lankenau Medical Center, Wynnewood, PA, USA
| | - Albert DeNittis
- Lankenau Medical Center, Wynnewood, PA, USA.,Lankenau Institute for Medical Research, Wynnewood, PA, USA
| | - Yibing Hu
- Lankenau Medical Center, Wynnewood, PA, USA
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Xu Y, Ma P, Xu Y, Dai J. Selection of prescription isodose line for brain metastases treated with volumetric modulated arc radiotherapy. J Appl Clin Med Phys 2019; 20:63-69. [PMID: 31833642 PMCID: PMC6909111 DOI: 10.1002/acm2.12761] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 08/26/2019] [Accepted: 09/23/2019] [Indexed: 12/13/2022] Open
Abstract
Purpose To exploit the optimal prescription isodose line (IDL) for brain metastases treated with volumetric modulated arc radiotherapy (VMAT) as there is no consensus on the selection of IDL with VMAT. Methods and materials Eighteen patients with 20 brain tumors, who were treated with VMAT, were enrolled in this study. For each tumor of every patient, five plans were designed with IDL ranging from 50% to 90% in 10% increments. Different IDLs were obtained through adjusting the constraint parameters during planning optimization. Prescription dose (10 × 5 Gy) were identical for all plans, and the plans were compared in terms of gradient index (GI), conformity Index (CI), V26 Gy/VPTV, and V32 Gy/VPTV in normal brain tissue, which correlate to radiation necrosis. Results IDL with lowest GI has a median value of 60.0% (ranging from 50% to 80%). Except for one tumor with volume larger than 10 cc, the IDL with lowest GI varies from 50% to 70%, which depends on the shape of PTV, location, and whether the target volume is adjacent to crucial OAR. Moreover, there is no significant difference for CI with varying IDL plans. The average V26 Gy/VPTV and V32 Gy/VPTV in normal brain tissue 60% IDL plans are 27.3%, 31.7% lower than 90% IDL plans separately (P < 0.05). However, by further decreasing IDL from 60% to 50%, the average V26 Gy/VPTV and V32 Gy/VPTV may increase comparing with 60% IDL plans (P > 0.05). Furthermore, a lower IDL is found to result in higher mean dose to the target volume (P < 0.05). Conclusions Plans using VMAT with PTV smaller than 10 cc tend to be optimal with IDL around 60–70% for lower GI, smaller V26 Gy/VPTV, V32 Gy/VPTV in normal brain tissue, and higher mean dose in tumor comparing with high IDL plans which have potential benefit in reducing risk of radiation necrosis and increasing the local control. However, IDL lower than 60% is not recommended for the disadvantage of increasing V26 Gy/VPTV and V32 Gy/VPTV in normal brain tissue.
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Affiliation(s)
- Yuan Xu
- Department of Radiation OncologyNational Cancer Center/National Clinical Research Center for Cancer/Cancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijingChina
| | - Pan Ma
- Department of Radiation OncologyNational Cancer Center/National Clinical Research Center for Cancer/Cancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijingChina
| | - Yingjie Xu
- Department of Radiation OncologyNational Cancer Center/National Clinical Research Center for Cancer/Cancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijingChina
| | - Jianrong Dai
- Department of Radiation OncologyNational Cancer Center/National Clinical Research Center for Cancer/Cancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijingChina
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Tsurugai Y, Takeda A, Sanuki N, Eriguchi T, Aoki Y, Oku Y, Akiba T, Sugawara A, Kunieda E. Stereotactic body radiotherapy for patients with non-small-cell lung cancer using RapidArc delivery and a steep dose gradient: prescription of 60% isodose line of maximum dose fitting to the planning target volume. J Radiat Res 2019; 60:364-370. [PMID: 30668868 PMCID: PMC6530627 DOI: 10.1093/jrr/rry112] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 10/26/2018] [Indexed: 06/09/2023]
Abstract
We retrospectively investigated outcomes, including pulmonary toxicities, of stereotactic body radiation therapy using RapidArc and a risk-adapted 60% isodose plan for early-stage non-small-cell lung cancer patients. We evaluated patients staged as cT1a-2bN0M0 between 2011 and 2017 and treated with a total dose of 40-60 Gy in five fractions to the 60% isodose line of the maximum dose encompassing the planning target volume with curative intent. Comorbidities and age were rated using an age-adjusted Charlson comorbidity index (AACCI). Factors associated with overall survival (OS) were investigated. A total of 237 patients with 250 lesions were eligible. The median follow-up was 28.0 months. The local recurrence rate at 3 years was 0.8%; none of the patients developed isolated local recurrence. OS, deaths from lung cancer, and deaths from intercurrent disease at 3 years were 72.7%, 8.2% and 19.1%, respectively. On multivariate analysis for correlating factors with OS, AACCI and maximal standardized uptake value on [18F]-fluorodeoxyglucose positron emission tomography/computed tomography remained significant. Grade ≥3 toxicities were limited to radiation pneumonitis in six (2.4%) patients (Grade 3 in four patients and Grade 5 in two patients). Among those, three patients had idiopathic interstitial pneumonia. The total dose was unrelated to the incidence of Grade ≥3 radiation pneumonitis (P = 0.69). Using the 60% isodose prescription and RapidArc, maximal local control was achieved with acceptable toxicities. Although the OS may depend on patient background, dose escalation aiming at higher local control can be beneficial for medically inoperable patients.
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Affiliation(s)
- Yuichiro Tsurugai
- Radiation Oncology Center, Ofuna Chuo Hospital, 6-2-24 Ofuna, Kamakura, Kanagawa, Japan
| | - Atsuya Takeda
- Radiation Oncology Center, Ofuna Chuo Hospital, 6-2-24 Ofuna, Kamakura, Kanagawa, Japan
| | - Naoko Sanuki
- Radiation Oncology Center, Ofuna Chuo Hospital, 6-2-24 Ofuna, Kamakura, Kanagawa, Japan
| | - Takahisa Eriguchi
- Radiation Oncology Center, Ofuna Chuo Hospital, 6-2-24 Ofuna, Kamakura, Kanagawa, Japan
| | - Yousuke Aoki
- Radiation Oncology Center, Ofuna Chuo Hospital, 6-2-24 Ofuna, Kamakura, Kanagawa, Japan
| | - Yohei Oku
- Radiation Oncology Center, Ofuna Chuo Hospital, 6-2-24 Ofuna, Kamakura, Kanagawa, Japan
| | - Takeshi Akiba
- Radiation Oncology Center, Ofuna Chuo Hospital, 6-2-24 Ofuna, Kamakura, Kanagawa, Japan
- Department of Radiation Oncology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, Japan
| | - Akitomo Sugawara
- Department of Radiation Oncology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, Japan
| | - Etsuo Kunieda
- Department of Radiation Oncology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, Japan
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