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Ding Z, Xiang X, Kang K, Zeng Q, Yuan Q, Xu M. Comparison of dosimetric characteristics between flattening filter‐free and flattening filter mode volumetric‐modulated arc therapy plans in rectal cancer. PRECISION RADIATION ONCOLOGY 2021. [DOI: 10.1002/pro6.1117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Zhen Ding
- National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital Chinese Academy of Medical Sciences and Peking Union Medical College Shenzhen Guangdong Province China
| | - Xiaoyong Xiang
- National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital Chinese Academy of Medical Sciences and Peking Union Medical College Shenzhen Guangdong Province China
| | - Kailian Kang
- National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital Chinese Academy of Medical Sciences and Peking Union Medical College Shenzhen Guangdong Province China
| | - Qi Zeng
- National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital Chinese Academy of Medical Sciences and Peking Union Medical College Shenzhen Guangdong Province China
| | - Qingqing Yuan
- National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital Chinese Academy of Medical Sciences and Peking Union Medical College Shenzhen Guangdong Province China
| | - Meiling Xu
- National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital Chinese Academy of Medical Sciences and Peking Union Medical College Shenzhen Guangdong Province China
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Liu C, Liao L, Wu G, Yan H, Chen X, Wang C, Zheng X, Zeng Z, Zhao Z, Wu D, Liu X. Radiation-induced second primary squamous cell carcinoma of the oral cavity after radiotherapy for nasopharyngeal carcinoma. Oral Oncol 2020; 109:104863. [PMID: 32604060 DOI: 10.1016/j.oraloncology.2020.104863] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 05/10/2020] [Accepted: 06/14/2020] [Indexed: 12/08/2022]
Abstract
BACKGROUND The increasing occurrence of radiation-induced second primary squamous cell carcinoma of the oral cavity (RISCCO) after radiotherapy for nasopharyngeal carcinoma (NPC) has become a noteworthy complication that can influence long-term survival. This study aimed to analyze the associations of clinicopathologic characteristics with prognostic factors among patients who developed RISCCO after radiotherapy for NPC. METHODS A total of 41,446 NPC patients admitted to Sun Yat-sen University Cancer Center (SYSUCC) between August 1989 and January 2019 were reviewed. Among these patients, 88 RISCCO patients who satisfied the inclusion criteria were included in the study. RESULTS During our study, the incidence of RISCCO after radiotherapy was 0.21% (88/41,446) among NPC patients at SYSUCC. The latency period ranged from 1.0 to 34.0 years (median, 9.0 years), and the latency of RISCCO was notably shorter for patients who received intensity-modulated radiation therapy than that for patients who received conventional radiotherapy using cobalt-60 or 6-MV X-rays (median, 4.0 years vs. 11.0 years, P = 0.013). The 1-, 3-, and 5-year overall survival (OS) rates for the entire cohort of 88 patients were 79.0%, 46.6%, and 35.2%, respectively. The 5-year OS rate for the 79 patients who received treatment was 45.7%, and the 5-year OS rate for the 9 patients who refused treatment was 0%. T classification and surgery were identified as independent prognostic factors associated with a high OS rate. CONCLUSIONS Surgery as the first-choice treatment may improve survival and prognosis. A long-term follow-up is needed for early detection of RISCCO in NPC patients.
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Affiliation(s)
- Chao Liu
- School of Stomatology, Jilin University, Changchun 130041, Jilin, PR China
| | - Lieqiang Liao
- Department of Otolaryngology Head and Neck Surgery, The First People's Hospital of Foshan, Foshan, Guangdong, PR China
| | - Guoying Wu
- Guangdong Provincial Hospital of Integrated Traditional Chinese and Western Medicine, PR China
| | - Honghong Yan
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Head and Neck Surgery, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong 510060, PR China
| | - Xiaoqi Chen
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Head and Neck Surgery, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong 510060, PR China
| | - Chao Wang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Head and Neck Surgery, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong 510060, PR China
| | - Xiajing Zheng
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Head and Neck Surgery, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong 510060, PR China
| | - Ziyi Zeng
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Radiation Oncology, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong 510060, PR China
| | - Zheng Zhao
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Head and Neck Surgery, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong 510060, PR China
| | - Di Wu
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Head and Neck Surgery, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong 510060, PR China
| | - Xuekui Liu
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Head and Neck Surgery, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong 510060, PR China.
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Tanaka Y, Akino Y, Mizuno H, Isono M, Masai N, Yamamoto T. Impact of detector selections on inter-institutional variability of flattening filter-free beam data for TrueBeam™ linear accelerators. J Appl Clin Med Phys 2019; 21:36-42. [PMID: 31738002 PMCID: PMC6964765 DOI: 10.1002/acm2.12766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/11/2019] [Accepted: 10/14/2019] [Indexed: 11/08/2022] Open
Abstract
This study evaluates the type of detector influencing the inter-institutional variability in flattening filter-free (FFF) beam-specific parameters for TrueBeam™ linear accelerators (Varian Medical Systems,Palo Alto, CA, USA). Twenty-four beam data sets, including the percent depth dose (PDD), off-center ratio (OCR), and output factor (OPF) for modeling within the Eclipse (Varian Medical Systems) treatment planning system, were collected from 19 institutions. Although many institutions collected the data using CC13 (IBA Dosimetry, Schwarzenbruck, Germany) or PTW31010 semiflex (PTW Freiburg, Freiburg, Germany) ionization chambers, some institutions used diode detectors, diamond detectors, and ionization chambers with smaller cavities. The OCR data included penumbra width, full width at half maximum (FWHM), and FFF beam-specific parameters, including unflatness and slope. The data measured by CC13/PTW31010 ionization chambers were compared with those measured by all other detectors. PDD data demonstrated the variations within ±1% at the dose fall-off region deeper than peak depth. The penumbra widths of the OCR measured with the CC13/PTW31010 detectors were significantly larger than those measured with all other detectors (P < 0.05). Especially the EDGE detector (Sun Nuclear Corp., Melbourne, FL, USA) and the microDiamond detectors (model 60019; PTW Freiburg) demonstrated much smaller penumbra values compared to those of the CC13/PTW31010 detectors for the 30 × 30 mm2 field. There was no difference in the FWHM, unflatness, and slope parameters between the values for the CC13/PTW31010 detectors and all other detectors. OPF curves demonstrated small variations, and the relative difference from the mean value of each data point was almost within 1% for all field sizes. Although the penumbra region exhibited detector-dependent variations, all other parameters showed tiny interunit variations regardless of the detector type.
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Affiliation(s)
- Yoshihiro Tanaka
- Department of Radiation Therapy, Japanese Red Cross Society Kyoto Daiichi Hospital, Kyoto, Japan
| | - Yuichi Akino
- Oncology Center, Osaka University Hospital, Suita, Osaka, Japan
| | - Hirokazu Mizuno
- Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Masaru Isono
- Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
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Sadrollahi A, Nuesken F, Licht N, Rübe C, Dzierma Y. Monte-Carlo simulation of the Siemens Artiste linear accelerator flat 6 MV and flattening-filter-free 7 MV beam line. PLoS One 2019; 14:e0210069. [PMID: 30620742 PMCID: PMC6324801 DOI: 10.1371/journal.pone.0210069] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 12/17/2018] [Indexed: 11/18/2022] Open
Abstract
The aim of our work is to provide the up-to-now missing information on the Siemens Artiste FFF 7 MV beam line using a Monte-Carlo model fit to the realistic dosimetric measurements at the linear accelerator in clinical use at our department. The main Siemens Artiste 6MV and FFF 7MV beams were simulated using the Geant4 toolkit. The simulations were compared with the measurements with an ionization chamber in a water phantom to verify the validation of simulation and tuning the primary electron parameters. Hereafter, other parameters such as surface dose, spectrum, electron contamination, symmetry, flatness/unflatness, slope, and characteristic off-axis changes were discussed for both Flat and FFF mode. The mean electron energy for the FFF beam was 8.8 MeV and 7.5 MeV for Flat 6 MV, the spread energy and spot size of the selected Gaussian distribution source were 0.4 MeV and 1mm, respectively. The dose rate of the FFF beam was 2.8 (2.96) times higher than for the flattened beam for a field size of 10×10 (20×20) cm2. The electron contamination has significant contribution to the surface dose especially for the flattened beam. The penumbra, surface dose and the mean energy of photons decrease by removing the flattening filter. Finally, the results show that off-axis changes have no strong effect on the mean energy of FFF beams, while this effect was more considerable for the flattened beam.
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Affiliation(s)
- Alemeh Sadrollahi
- Department of Radiotherapy and Radiation Oncology, Saarland University Medical Center, Homburg, Saarland, Germany
- * E-mail:
| | - Frank Nuesken
- Department of Radiotherapy and Radiation Oncology, Saarland University Medical Center, Homburg, Saarland, Germany
| | - Norbert Licht
- Department of Radiotherapy and Radiation Oncology, Saarland University Medical Center, Homburg, Saarland, Germany
| | - Christian Rübe
- Department of Radiotherapy and Radiation Oncology, Saarland University Medical Center, Homburg, Saarland, Germany
| | - Yvonne Dzierma
- Department of Radiotherapy and Radiation Oncology, Saarland University Medical Center, Homburg, Saarland, Germany
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Jia F, Xu D, Yue H, Wu H, Li G. Comparison of Flattening Filter and Flattening Filter-Free Volumetric Modulated Arc Radiotherapy in Patients with Locally Advanced Nasopharyngeal Carcinoma. Med Sci Monit 2018; 24:8500-8505. [PMID: 30472719 PMCID: PMC6276721 DOI: 10.12659/msm.910218] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND This study aimed to investigate the therapeutic role of flattening filter-free (FFF) mode in volumetric modulated arc therapy (VMAT) compared with flattening filter (FF) mode in patients with locally advanced nasopharyngeal carcinoma (NPC). MATERIAL AND METHODS Ten previously treated patients with NPC underwent treatment re-planning with FFF and FF VMAT. Radiotherapy dose distribution on planning target volume (PTV), organs at risk (OAR), target conformity index (CI), total monitor units (MUs), and therapeutic time were compared. RESULTS Maximum and mean radiotherapy dose in PTV and PGTV (primary lesions of NPC and cervical lymph node metastases) in FFF VMAT planning were significantly increased compared with FF VMAT planning, but PTV and OAR showed no significant differences. The CI value of PTV in FFF VMAT planning was significantly reduced compared with FF planning (P<0.05). No differences were found for the maximum radiotherapy dose in the spinal cord and left and right optic nerve, and the mean radiotherapy dose in the brainstem, left and right parotid gland (P>0.05). The maximum dose in the brainstem in the FFF planning was significantly higher compared with FF planning (P>0.05). The maximum radiotherapy dose in left and right crystalline lens (P<0.05) in FFF planning was significantly reduced compared with FF planning. The total hop count in FFF planning was significantly increased compared with FF planning (P<0.05). CONCLUSIONS Both 6 MV X-ray FFF mode and FF mode in the treatment of patients with NPC showed that FFF VMAT planning provided improved protection for OAR.
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Affiliation(s)
- Fei Jia
- Department of Radiation Oncology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China (mainland)
| | - Dandan Xu
- Department of Radiation Oncology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China (mainland)
| | - Haizhen Yue
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiotherapy, Peking University Cancer Hospital and Institute, Beijing, China (mainland)
| | - Hao Wu
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiotherapy, Peking University Cancer Hospital and Institute, Beijing, China (mainland)
| | - Guowen Li
- Department of Radiation Oncology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China (mainland)
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Dzierma Y, Nuesken F, Licht N, Rübe C. Benchmarking the mARC performance – treatment time and dosimetric linearity. Z Med Phys 2016; 26:339-348. [PMID: 26947444 DOI: 10.1016/j.zemedi.2016.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 01/07/2016] [Accepted: 02/01/2016] [Indexed: 10/22/2022]
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Maier J, Knott B, Maerz M, Loeschel R, Koelbl O, Dobler B. Simultaneous integrated boost (SIB) radiation therapy of right sided breast cancer with and without flattening filter - A treatment planning study. Radiat Oncol 2016; 11:111. [PMID: 27577561 PMCID: PMC5006633 DOI: 10.1186/s13014-016-0687-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Accepted: 08/19/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The aim of the study was to compare the two irradiation modes with (FF) and without flattening filter (FFF) for three different treatment techniques for simultaneous integrated boost radiation therapy of patients with right sided breast cancer. METHODS An Elekta Synergy linac with Agility collimating device is used to simulate the treatment of 10 patients. Six plans were generated in Monaco 5.0 for each patient treating the whole breast and a simultaneous integrated boost (SIB) volume: intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT) and a tangential arc VMAT (tVMAT), each with and without flattening filter. Plan quality was assessed considering target coverage, sparing of the contralateral breast, the lungs, the heart and the normal tissue. All plans were verified by a 2D-ionisation-chamber-array and delivery times were measured and compared. The Wilcoxon test was used for statistical analysis with a significance level of 0.05. RESULTS Significantly best target coverage and homogeneity was achieved using VMAT FFF with V95% = (98.7 ± 0.8) % and HI = (8.2 ± 0.9) % for the SIB and V95% = (98.3 ± 0.7) % for the PTV, whereas tVMAT showed significantly lowest doses to the contralateral organs at risk with a Dmean of (0.7 ± 0.1) Gy for the contralateral lung, (1.0 ± 0.2) Gy for the contralateral breast and (1.4 ± 0.2) Gy for the heart. All plans passed the gamma evaluation with a mean passing rate of (99.2 ± 0.8) %. Delivery times were significantly reduced for VMAT and tVMAT but increased for IMRT, when FFF was used. Lowest delivery times were observed for tVMAT FFF with (1:20 ± 0:07) min. CONCLUSION Balancing target coverage, OAR sparing and delivery time, VMAT FFF and tVMAT FFF are considered the preferable of the investigated treatment options in simultaneous integrated boost irradiation of right sided breast cancer for the combination of an Elekta Synergy linac with Agility and the treatment planning system Monaco 5.0.
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Affiliation(s)
- Johannes Maier
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany
| | - Bernadette Knott
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany
| | - Manuel Maerz
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany
| | - Rainer Loeschel
- Ostbayerische Technische Hochschule Regensburg, Faculty of Computer Science and Mathematics, Regensburg, Germany
| | - Oliver Koelbl
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany
| | - Barbara Dobler
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
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Valdenaire S, Mailleux H, Fau P. Modeling of flattening filter free photon beams with analytical and Monte Carlo TPS. Biomed Phys Eng Express 2016. [DOI: 10.1088/2057-1976/2/3/035010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Nithya L, Raj NAN, Rathinamuthu S. Analyzing the characteristics of 6 MV photon beam at low monitor unit settings. J Med Phys 2016; 41:34-7. [PMID: 27051168 PMCID: PMC4795415 DOI: 10.4103/0971-6203.177285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Analyzing the characteristics of a low monitor unit (MU) setting is essential, particularly for intensity-modulated techniques. Intensity modulation can be achieved through intensity-modulated radiotherapy (IMRT) or volumetric-modulated arc therapy (VMAT). There is possibility for low MUs in the segments of IMRT and VMAT plans. The minimum MU/segment must be set by the physicist in the treatment planning system at the time of commissioning. In this study, the characteristics such as dose linearity, stability, flatness, and symmetry of 6 MV photon beam of a Synergy linear accelerator at low MU settings were investigated for different dose rates. The measurements were performed for Synergy linear accelerator using a slab phantom with a FC65-G chamber and Profiler 2. The MU linearity was studied for 1–100 MU using a field size of 10 cm ×10 cm. The linearity error for 1 MU was 4.2%. Flatness of the beam was deteriorated in 1 MU condition. The beam stability and symmetry was well within the specification. Using this study, we conclude that the treatment delivered with <3 MU may result in uncertainty in dose delivery. To ensure the correct dose delivery with less uncertainty, it is recommended to use ≥3 MU as the minimum MU per segment in IMRT and VMAT plans.
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Affiliation(s)
- L Nithya
- Department of Radiation Oncology, Dharamshila Hospital and Research Centre, New Delhi, India
| | - N Arunai Nambi Raj
- Department of Physics, School of Advanced Sciences, VIT University, Vellore, Tamil Nadu, India
| | - Sasikumar Rathinamuthu
- Department of Radiation Oncology, Dharamshila Hospital and Research Centre, New Delhi, India
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Dobler B, Khemissi A, Obermeier T, Hautmann MG, Katsilieri Z, Kölbl O. Re-irradiating spinal column metastases using IMRT and VMAT with and without flattening filter - a treatment planning study. Radiat Oncol 2016; 11:33. [PMID: 26932561 PMCID: PMC4774147 DOI: 10.1186/s13014-016-0603-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 02/18/2016] [Indexed: 01/16/2023] Open
Abstract
Background The aim of this study was to investigate the potential of the flattening filter free (FFF) mode of a linear accelerator for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for patients with in-field recurrence of vertebral metastases. Methods An Elekta Synergy Linac with Agility™ head is used to simulate the treatment of ten patients with locally recurrent spinal column metastases. Four plans were generated for each patient treating the vertebrae sparing the spinal cord: Dual arc VMAT and nine field step and shoot IMRT each with and without flattening filter. Plan quality was assessed considering target coverage and sparing of the spinal cord and normal tissue. All plans were verified by a 2D-ionisation-chamber-array, peripheral doses were measured and compared to calculations. Delivery times were measured and compared. The Wilcoxon test was used for statistical analysis with a significance level of 0.05. Results Target coverage, homogeneity index and conformity index were comparable for both flat and flattening filter free beams. The volume of the spinal cord receiving the allowed maximum dose to keep the risk of radiation myelopathy at 0 % was at the same time significantly reduced to below the clinically relevant 1 ccm using FFF mode. In addition the mean dose deposited in the surrounding healthy tissue was significantly reduced in the FFF mode. All four techniques showed equally good gamma scores for plan verification. FFF plans required considerably more MU per fraction dose. Regardless of the large number of MU, out-of-field point dose was significantly lower for FFF plans, with an average reduction of 33 % and mean delivery time was significantly reduced by 22 % using FFF beams. When compared to IMRT FF, VMAT FFF offered even a reduction of 71 % in delivery time and 45 % in peripheral dose. Conclusions FFF plans showed a significant improvement in sparing of normal tissue and the spinal cord, keeping target coverage and homogeneity comparable. In addition, delivery times were significantly reduced for FFF treatments, minimizing intrafractional motion as well as strain for the patient. Shortest delivery times were achieved using VMAT FFF. For radiotherapy of spinal column metastases VMAT FFF may therefore be considered the preferable treatment option for the combination of Elekta Synergy Linacs and Oncentra® External Beam v4.5 treatment planning system.
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Affiliation(s)
- Barbara Dobler
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
| | - Amine Khemissi
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
| | - Tina Obermeier
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
| | - Matthias G Hautmann
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
| | - Zaira Katsilieri
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
| | - Oliver Kölbl
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany.
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