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Sharma S, Dixit DK, Sharma SD, Sharma A, Sahani G, Upreti RR, Kinhikar RA, Sharma PKD. A Simplified Approach for Determination of Inflection Points of Flattening Filter-Free Photon Beam Using In-House Developed Software and Derivation of Reference Levels. J Med Phys 2023; 48:259-267. [PMID: 37969146 PMCID: PMC10642602 DOI: 10.4103/jmp.jmp_50_23] [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: 04/20/2023] [Revised: 07/01/2023] [Accepted: 07/06/2023] [Indexed: 11/17/2023] Open
Abstract
Aim This article aimed to present the salient features of the in-house developed Java program for the determination of inflection point and dosimetric parameters of flattening filter-free (FFF) photon beam. Reference levels for the dosimetric parameters of the FFF photon beams were also presented. Materials and Methods Beam profiles of 6 MV FFF and 10 MV FFF photon beams for a collimator setting of 20 cm × 20 cm measured at 10 cm depth in an isocentric setup acquired from various institutions were analyzed using an in-house developed Java program and manual method. The values of reference dose value (RDV), field size, penumbra, and degree of un-flatness (defined as the lateral separation between 90% [X90%], 75% [X75%], and 60% [X60%] dose points on the profile) were calculated and compared. The reference values of field size, penumbra, and degree of un-flatness were also determined for Varian and Elekta medical electron linear accelerators (LINACs). Results The maximum differences for RDV determined using the Java method and manual method are 2.4% and 2.7% for 6 and 10 MV FFF photon beams, respectively. The maximum difference between the values of field size, penumbra, and degree of un-flatness determined using Java and manual methods is within 1.3 mm. The reference values of field size and penumbra for Varian LINACs are 19.94 ± 0.10 cm and 0.83 ± 0.08 cm (6 MV FFF) and 19.95 ± 0.10 cm and 0.83 ± 0.08 cm (10 MV FFF). Similarly, the reference values of field size and penumbra for Elekta LINACs are 20.02 ± 0.09 cm and 0.94 ± 0.12 cm (6 MV FFF) and 20.03 ± 0.11 cm and 0.97 ± 0.16 cm (10 MV FFF). Conclusions A software program was developed in Java for analyzing the beam profiles of FFF photon beams. The results of Java-derived values of dosimetric parameters of FFF photon beams were found in good agreement with the values determined using the manual method. The reference values of these parameters were also derived and quoted using a large cohort of the data.
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Affiliation(s)
- Smriti Sharma
- Radiological Safety Division, Atomic Energy Regulatory Board, Mumbai, Maharashtra, India
- Homi Bhabha National Institute, Mumbai, Maharashtra, India
| | - D. K. Dixit
- Computer Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
| | - S. D. Sharma
- Homi Bhabha National Institute, Mumbai, Maharashtra, India
- Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
| | - Amit Sharma
- Atomic Fuels Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
| | - G. Sahani
- Radiological Safety Division, Atomic Energy Regulatory Board, Mumbai, Maharashtra, India
| | - Ritu Raj Upreti
- Department of Medical Physics, Tata Memorial Centre, Mumbai, Maharashtra, India
| | - R. A. Kinhikar
- Homi Bhabha National Institute, Mumbai, Maharashtra, India
- Department of Medical Physics, Tata Memorial Centre, Mumbai, Maharashtra, India
| | - P. K. Dash Sharma
- Radiological Safety Division, Atomic Energy Regulatory Board, Mumbai, Maharashtra, India
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Saroj DK, Yadav S, Paliwal N, Haldar S, Jagtap A, Kumar A. Assessment of Treatment Plan Quality between Flattening Filter and Flattening Filter Free Photon Beam for Carcinoma of the Esophagus with IMRT Technique. J Biomed Phys Eng 2023; 13:227-238. [PMID: 37312893 PMCID: PMC10258210 DOI: 10.31661/jbpe.v0i0.2108-1381] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 03/17/2022] [Indexed: 06/15/2023]
Abstract
Background As compared to the flattened photon beam, removing the flattening filter (FF) from the head of a gantry decreases the average energy of the photon beam and increases the dose rate, leading to an impact on the quality of treatment plans. Objective This study aimed to compare the quality of intensity-modulated radiation therapy (IMRT) treatment plans for esophageal cancer with and without a flattened filter photon beam. Material and Methods In this analytical study, 12 patients, who had already been treated with a 6X FF photon beam, were treated based on new IMRT methods using a 6X the flattening filter-free (FFF) photon beam. Both 6X FF IMRT and 6X FFF IMRT plans used identical beam parameters and planning objectives. All plans were evaluated with planning indices and doses for organs at risk (OARs). Results Insignificant dose variation was for HI, CI, D98%, and V95% between FF and FFF photon beam IMRT plans. FF-based IMRT plan delivered a 15.51 % and 11.27% higher mean dose to both lungs and heart than the FFF plan, respectively. The integral dose (ID) for the heart and lungs was 11.21% and 15.51%, respectively, less in the IMRT plan with an FFF photon beam. Conclusion In contrast to the FF photon beam, a filtered photon beam-oriented IMRT plan provides significant OAR sparing without losing the quality of the treatment plan. High monitor units (MUs), low ID, and Beam on Time (BOT) are major highlights of the IMRT plan with FFF beam.
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Affiliation(s)
- Dinesh Kumar Saroj
- Department of Radiotherapy, Alexis Multispecialty Hospital Nagpur-440030 (Maharashtra), India
- Department of Science, Rabindranath Tagore University, Bhopal, Madhya Pradesh, India
| | - Suresh Yadav
- Department of Radiotherapy, Gandhi Medical College, Bhopal-462001 (M.P.), India
| | - Neetu Paliwal
- Department of Science, Rabindranath Tagore University, Bhopal, Madhya Pradesh, India
| | - Subhas Haldar
- Department of Radiotherapy, Saroj Gupta Cancer Center and Research Institute, Kolkata-700063 (West Bengal), India
| | - Amol Jagtap
- Department of Radiotherapy, Alexis Multispecialty Hospital Nagpur-440030 (Maharashtra), India
| | - Arvind Kumar
- Department of Radiation Oncology, All India Institute of Medical Sciences (AIIMS), Rishikesh-249203 (U.K.), India
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Monte Carlo computation of photon energy spectra in central axis of flattened and unflattened beams and doses in critical organs in a water phantom model of prostate radiotherapy. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2022.110211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Amoabeng KA, Marthinsen ABL, Hasford F, Tagoe SNA, Anaafi E. Verification of patient specific quality assurance system for volumetric modulated arc therapy (VMAT). HEALTH AND TECHNOLOGY 2022. [DOI: 10.1007/s12553-022-00675-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Park H, Paganetti H, Schuemann J, Jia X, Min CH. Monte Carlo methods for device simulations in radiation therapy. Phys Med Biol 2021; 66:10.1088/1361-6560/ac1d1f. [PMID: 34384063 PMCID: PMC8996747 DOI: 10.1088/1361-6560/ac1d1f] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 08/12/2021] [Indexed: 11/12/2022]
Abstract
Monte Carlo (MC) simulations play an important role in radiotherapy, especially as a method to evaluate physical properties that are either impossible or difficult to measure. For example, MC simulations (MCSs) are used to aid in the design of radiotherapy devices or to understand their properties. The aim of this article is to review the MC method for device simulations in radiation therapy. After a brief history of the MC method and popular codes in medical physics, we review applications of the MC method to model treatment heads for neutral and charged particle radiation therapy as well as specific in-room devices for imaging and therapy purposes. We conclude by discussing the impact that MCSs had in this field and the role of MC in future device design.
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Affiliation(s)
- Hyojun Park
- Department of Radiation Convergence Engineering, Yonsei University, Wonju, Republic of Korea
| | - Harald Paganetti
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States of America
| | - Jan Schuemann
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States of America
| | - Xun Jia
- Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX 75235, United States of America
| | - Chul Hee Min
- Department of Radiation Convergence Engineering, Yonsei University, Wonju, Republic of Korea
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Kodama T, Yasui K, Nishioka S, Miyaura K, Takakura T, Katayose T, Nakamura M. Survey on utilization of flattening filter-free photon beams in Japan. JOURNAL OF RADIATION RESEARCH 2021; 62:726-734. [PMID: 34036361 PMCID: PMC8273795 DOI: 10.1093/jrr/rrab042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 03/08/2021] [Indexed: 06/12/2023]
Abstract
To understand the current state of flattening filter-free (FFF) beam implementation in C-arm linear accelerators (LINAC) in Japan, the quality assurance (QA)/quality control (QC) 2018-2019 Committee of the Japan Society of Medical Physics (JSMP) conducted a 37-question survey, designed to investigate facility information and specifications regarding FFF beam adoption and usage. The survey comprised six sections: facility information, devices, clinical usage, standard calibration protocols, modeling for treatment planning (TPS) systems and commissioning and QA/QC. A web-based questionnaire was developed. Responses were collected between 18 June and 18 September 2019. Of the 846 institutions implementing external radiotherapy, 323 replied. Of these institutions, 92 had adopted FFF beams and 66 had treated patients using them. FFF beams were used in stereotactic radiation therapy (SRT) for almost all disease sites, especially for the lungs using 6 MV and liver using 10 MV in 51 and 32 institutions, respectively. The number of institutions using FFF beams for treatment increased yearly, from eight before 2015 to 60 in 2018. Farmer-type ionization chambers were used as the standard calibration protocol in 66 (72%) institutions. In 73 (80%) institutions, the beam-quality conversion factor for FFF beams was calculated from TPR20,10, via the same protocol used for beams with flattening filter (WFF). Commissioning, periodic QA and patient-specific QA for FFF beams also followed the procedures used for WFF beams. FFF beams were primarily used in high-volume centers for SRT. In most institutions, measurement and QA was conducted via the procedures used for WFF beams.
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Affiliation(s)
- Takumi Kodama
- Department of Radiation Oncology, Saitama Cancer Center, 780 Ooazakomuro, Inamachi, Kitaadachi-gun, Saitama 362-0806, Japan
| | - Keisuke Yasui
- Faculty of Radiological Technology, School of Health Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470–1192, Japan
| | - Shie Nishioka
- Department of Medical Physics, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104–0045, Japan
| | - Kazunori Miyaura
- Graduate School of Health Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142–8666, Japan
| | - Toru Takakura
- Department of Radiation Therapy, Uji-Tokushukai Medical Center, 145 Ishibashi, Makichima-cho, Uji-shi, Kyoto 611–0041, Japan
| | - Tetsurou Katayose
- Department of Radiation Oncology, Chiba Cancer Center, 666-2 Nitona-cho, Chuo-ku, Chiba 260–8717, Japan
| | - Mitsuhiro Nakamura
- Department of Information Technology and Medical engineering, Human Health Science, Graduate School of Medicine, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
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Tuğrul T. Effect of different target materials of LINAC head on photon spectrum. JOURNAL OF RADIATION RESEARCH AND APPLIED SCIENCES 2021. [DOI: 10.1080/16878507.2021.1921964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Taylan Tuğrul
- Department of Radiation Oncology, Medicine Faculty of Van Yüzüncü Yıl University, Van, Turkey
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García-Hernández T, Vicedo-González A, Sánchez-Nieto B, Romero-Expósito M, Roselló-Ferrando J. PERIPHERAL SURFACE DOSE FROM A LINEAR ACCELERATOR: RADIOCHROMIC FILM EXPERIMENTAL MEASUREMENTS OF FLATTENING FILTER FREE VERSUS FLATTENED BEAMS. RADIATION PROTECTION DOSIMETRY 2020; 188:285-298. [PMID: 31922571 DOI: 10.1093/rpd/ncz286] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 11/06/2019] [Accepted: 11/26/2019] [Indexed: 06/10/2023]
Abstract
There is a growing interest in the use of flattening filter free (FFF) beams due to the shorter treatment times. The reduction of head scatter suggests a better radiation protection to radiotherapy patients, considering the expected decrease in peripheral surface dose (PSD). In this work, PSD of flattened (FF) and FFF-photon beams was compared. A radiochromic film calibration method to reduce energy dependence was used. PSD was measured at distances from 2 to 50 cm to the field border for different square field sizes, modifying relevant clinical parameters. Also, clinical breast and prostate stereotactic body radiotherapy (SBRT) plans were studied. For square beams, FFF PSD is lower compared with FF PSD (differences ranging from 3 to 64%) and 10 MV FFF yields to the lowest value, for distances greater than 5 cm. For SBRT plans, near and far away from the field border, there is a reduction of PSD for FFF-beams, but the behavior at intermediate distances should be checked depending on the case.
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Affiliation(s)
| | - Aurora Vicedo-González
- Departmento de Física Médica, ERESA Hospital General Universitario de Valencia, Valencia, Spain
| | | | | | - Joan Roselló-Ferrando
- Departmento de Física Médica, ERESA Hospital General Universitario de Valencia, Valencia, Spain
- Departamento de Fisiología, Universidad de Valencia, Valencia, Spain
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Potter NJ, Yan G, Liu H, Alahmad H, Kahler DL, Liu C, Li JG, Lu B. Beam flatness modulation for a flattening filter free photon beam utilizing a novel direct leaf trajectory optimization model. J Appl Clin Med Phys 2020; 21:142-152. [PMID: 32176453 PMCID: PMC7075388 DOI: 10.1002/acm2.12837] [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: 09/20/2019] [Revised: 12/02/2019] [Accepted: 01/26/2019] [Indexed: 11/30/2022] Open
Abstract
Flattening filter free (FFF) linear accelerators produce a fluence distribution that is forward peaked. Various dosimetric benefits, such as increased dose rate, reduced leakage and out of field dose has led to the growth of FFF technology in the clinic. The literature has suggested the idea of vendors offering dedicated FFF units where the flattening filter (FF) is removed completely and manipulating the beam to deliver conventional flat radiotherapy treatments. This work aims to develop an effective way to deliver modulated flat beam treatments, rather than utilizing a physical FF. This novel optimization model is an extension of the direct leaf trajectory optimization (DLTO) previously developed for volumetric modulated radiation therapy (VMAT) and is capable of accounting for all machine and multileaf collimator (MLC) dynamic delivery constraints, using a combination of linear constraints and a convex objective function. Furthermore, the tongue and groove (T&G) effect was also incorporated directly into our model without introducing nonlinearity to the constraints, nor nonconvexity to the objective function. The overall beam flatness, machine deliverability, and treatment time efficiency were assessed. Regular square fields, including field sizes of 10 × 10 cm2 to 40 × 40 cm2 were analyzed, as well as three clinical fields, and three arbitrary contours with "concave" features. Quantitative flatness was measured for all modulated FFF fields, and the results were comparable or better than their open FF counterparts, with the majority having a quantitative flatness of less than 3.0%. The modulated FFF beams, due to the included efficiency constraint, were able to achieve acceptable delivery time compared to their open FF counterpart. The results indicated that the dose uniformity and flatness for the modulated FFF beams optimized with the DLTO model can successfully match the uniformity and flatness of their conventional FF counterparts, and may even provide further benefit by taking advantage of the unique FFF beam characteristics.
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Affiliation(s)
- Nicholas J Potter
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Guanghua Yan
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Hongcheng Liu
- Department of Industrial & Systems Engineering, College of Engineering, University of Florida, Gainesville, FL, USA
| | - Haitham Alahmad
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Darren L Kahler
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Chihray Liu
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Jonathan G Li
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Bo Lu
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
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Pokhrel D, Halfman M, Sanford L. FFF-VMAT for SBRT of lung lesions: Improves dose coverage at tumor-lung interface compared to flattened beams. J Appl Clin Med Phys 2019; 21:26-35. [PMID: 31859456 PMCID: PMC6964748 DOI: 10.1002/acm2.12764] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/09/2019] [Accepted: 10/07/2019] [Indexed: 12/14/2022] Open
Abstract
Purpose To quantify the differences in dosimetry as a function of ipsilateral lung density and treatment delivery parameters for stereotactic, single dose of volumetric modulated arc therapy (VMAT) lung stereotactic body radiation therapy (SBRT) delivered with 6X flattening filter free (6X‐FFF) beams compared to traditional flattened 6X (6X‐FF) beams. Materials/methods Thirteen consecutive early stage I–II non‐small‐cell‐lung cancer (NSCLC) patients were treated with highly conformal noncoplanar VMAT SBRT plans (3–6 partial arcs) using 6X‐FFF beam and advanced Acuros‐based dose calculations to a prescription dose of 30 Gy in one fraction to the tumor margin. These clinical cases included relatively smaller tumor (island tumors) sizes (2.0–4.2 cm diameters) and varying average ipsilateral lung densities between 0.14 g/cc and 0.34 g/cc. Treatment plans were reoptimized with 6X‐FF beams for identical beam/arc geometries and planning objectives. For same target coverage, the organs‐at‐risk (OAR) dose metrics as a function of ipsilateral lung density were compared between 6X‐FFF and 6X‐FF plans. Moreover, monitor units (MU), beam modulation factor (MF) and beam‐on time (BOT) were evaluated. Results Both plans met the RTOG‐0915 protocol compliance. The ipsilateral lung density and the tumor location heavily influenced the treatment plans with 6X‐FFF and 6X‐FF beams, showing differences up to 12% for the gradient indices. For similar target coverage, 6X‐FFF beams showed better target conformity, lower intermediate dose‐spillage, and lower dose to the OAR. Additionally, BOT was reduced by a factor of 2.3 with 6X‐FFF beams compared to 6X‐FF beams. Conclusion While prescribing dose to the tumor periphery, 6X‐FFF VMAT plans for stereotactic single‐dose lung SBRT provided similar target coverage with better dose conformity, superior intermediate dose‐spillage (improved dose coverage at tumor interface), and improved OAR sparing compared to traditional 6X‐FF beams and significantly reduced treatment time. The ipsilateral lung density and tumor location considerably affected dose distributions requiring special attention for clinical SBRT plan optimization on a per‐patient basis. Clinical follow up of these patients for tumor local‐control rate and treatment‐related toxicities is in progress.
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Affiliation(s)
- Damodar Pokhrel
- Department of Radiation Medicine, Medical Physics Graduate Program, University of Kentucky, Lexington, KY, USA
| | - Matthew Halfman
- Department of Radiation Medicine, Medical Physics Graduate Program, University of Kentucky, Lexington, KY, USA
| | - Lana Sanford
- Department of Radiation Medicine, Medical Physics Graduate Program, University of Kentucky, Lexington, KY, USA
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Kaushik S, Punia R, Tyagi A. Study of Dosimetric Properties of Flattening Filter Free Photon Beam Passing through Cadmium Free Compensator Alloy. J Biomed Phys Eng 2019; 9:647-652. [PMID: 32039095 PMCID: PMC6943851 DOI: 10.31661/jbpe.v0i0.745] [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: 02/25/2017] [Accepted: 03/22/2017] [Indexed: 06/10/2023]
Abstract
BACKGROUND This study aims to investigate radiation beam geometry of Cyberknife beam and change in dosimetric characteristics of six megavoltage (6MV) flattening filter free (FFF) beam after passing through high density cadmium free compensator alloy. MATERIAL AND METHODS In this experimental study, changes in FFF beam dosimetric characteristics after passing through compensator alloy was measured. Transmitted intensity of FFF beam was measured in air by an ion chamber at a source to detector distance (SDD) of 800mm. Extended SDD measurement also has been performed at a distance of 1270mm to analyze scattering due to compensator. Linear attenuation coefficient (µeff) was measured for cadmium free compensator alloy using simple exponential attenuation model. Percentage depth doses (PDDs) have been measured by a radiation field analyzer with compensator material to observe the beam hardening and change in surface doses and depth doses. RESULTS Linear attenuation coefficient of compensator alloy was measured 0.042 (Standard Deviation ±0.00099) mm-1 and it was found that there is no change with increase in collimator size. Even after increasing distance source from detector, µeff has no change. PDDs were found to increase with thickness of compensator. PDD from a 60mm collimator size increased by 5% and 6% at a depth of 100mm and 200mm, respectively in water. PDD also increased with collimator size less significantly. Surface dose was found to decrease with increase in compensator thickness. CONCLUSION Cyberknife beam has been found to be narrow beam geometry. FFF beam contains lesser scattered photons. Presence of high density compensator filters out the soft x-ray photon causes significant dosimetric changes.
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Affiliation(s)
- S Kaushik
- PhD, DRP, Guru Jambheshwar University of Science and Technology, Hisar, Haryana, India
| | - R Punia
- PhD, Maharishi Dayanand University, Rohtak, Haryana, India
- PhD, Chaudhary Ranbir Singh University, Jind, Haryana, India
| | - A Tyagi
- PhD, DRP, BLK Super Speciality Hospital, New Delhi India
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Mahmoudi A, Geraily G, Shirazi A, Hadisi nia T. Penumbra reduction technique and factors affecting it in radiotherapy machines – Review study. Radiat Phys Chem Oxf Engl 1993 2019. [DOI: 10.1016/j.radphyschem.2018.12.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Kajaria A, Sharma N, Sharma S, Pradhan S, Mandal A, Aggarwal L. Monte Carlo Study of Unflattened Photon Beams Shaped by Multileaf Collimator. J Biomed Phys Eng 2019; 9:137-150. [PMID: 31214519 PMCID: PMC6538911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Accepted: 06/15/2016] [Indexed: 11/02/2022]
Abstract
INTRODUCTION This study investigates basic dosimetric properties of unflattened 6 MV photon beam shaped by multileaf collimator and compares them with those of flattened beams. MATERIALS AND METHODS Monte Carlo simulation model using BEAM code was developed for a 6MV photon beam based on Varian Clinic 600 unique performance linac operated with and without a flattening filter in beam line. Dosimetric features including lateral profiles, central axis depth dose, photon and electron spectra were calculated for flattened and unflattened cases, separately. RESULTS An increase in absolute depth dose with a factor of more than 2.4 was observed for unflattened beam which was dependent on depth. PDDs values were found to be lower for unflattened beam for all field sizes. Significant decrease in calculated mlc leakage was observed when the flattening filter was removed from the beam line. The total scatter factor, SCP was found to show less variation with field sizes for unflattened beam indicating a decrease in head scatter. The beam profiles for unflattened case are found to have lower relative dose value in comparison with flattened beam near the field edge, and it falls off faster with distance. CONCLUSION Our study showed that increase in the dose rate and lower peripheral dose could be considered as realistic advantages for unflattened 6MV photon beams.
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Affiliation(s)
- A. Kajaria
- School of Biomedical Engineering, Indian Institute of Technology (BHU), Varanasi, UP, India
| | - N. Sharma
- School of Biomedical Engineering, Indian Institute of Technology (BHU), Varanasi, UP, India
| | - Sh. Sharma
- School of Biomedical Engineering, Indian Institute of Technology (BHU), Varanasi, UP, India
| | - S. Pradhan
- Department of Radiotherapy and Radiation Medicine, Institute of Medical Science (BHU), Varanasi, UP, India
| | - A. Mandal
- Department of Radiotherapy and Radiation Medicine, Institute of Medical Science (BHU), Varanasi, UP, India
| | - L.M. Aggarwal
- Department of Radiotherapy and Radiation Medicine, Institute of Medical Science (BHU), Varanasi, UP, India
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Monasor Denia P, Castellet García MDC, Manjón García C, Quirós Higueras JD, de Marco Blancas N, Bonaque Alandí J, Juan Senabre XJ, Santos Serra A, López-Tarjuelo J. Comparison of detector performance in small 6 MV and 6 MV FFF beams using a Versa HD accelerator. PLoS One 2019; 14:e0213253. [PMID: 30856183 PMCID: PMC6411166 DOI: 10.1371/journal.pone.0213253] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 02/18/2019] [Indexed: 11/18/2022] Open
Abstract
1. BACKGROUND & PURPOSE Investigate the applicability of a series of detectors in small field dosimetry and the possible differences between their responses to FF and FFF beams. This work extends upon the series of detectors used by other authors to also include metal-oxide-semiconductor field-effect transistors (MOSFETs) detectors and radiochromic film. We also included a later correction of output factors (OFs) recommended by the recently published IAEA´s code of practice TRS 483 on dosimetry of small static fields used in external beam radiotherapy. 2. MATERIALS & METHODS The OFs, profiles, and PDDs of 6 MV and 6 MV FFF beams were measured with 11 different detectors using field sizes between 0.6 × 0.6 cm2 and 10 × 10 cm2. 3. RESULTS The OFs of the FFF beams were lower than those of the FF beams for field sizes larger than 3 × 3 cm2 but higher for field sizes smaller than 3 × 3 cm2. After applying the IAEA´s TRS 483 corrections, the final OFs were compatible with our initial results when considering uncertainties involved. Small-volume detectors are preferable for measuring the penumbra of these small fields where this attribute is higher in the crossline direction than in the inline direction. The R100 of equivalent-quality FFF beams was higher compared to the corresponding flattened beams. 4. CONCLUSIONS We observed no difference for the dose responses between 6 MV and 6 MV FFF beams for any of the detectors. OF results, profiles and PDDs were clearly consistent with the previously published literature regarding the Versa HD linac. Correcting our first OFs, taken as ratio of detector charges, with the IAEA´s TRS 483 corrections to obtain the final OFs, did not make the former significantly different.
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Affiliation(s)
- Paula Monasor Denia
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | | | - Carla Manjón García
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Juan David Quirós Higueras
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Noelia de Marco Blancas
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Jorge Bonaque Alandí
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Xavier Jordi Juan Senabre
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Agustín Santos Serra
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Juan López-Tarjuelo
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
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15
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Potter NJ, Lebron S, Li JG, Liu C, Lu B. Feasibility study of using flattening-filter-free photon beams to deliver conventional flat beams. Med Dosim 2019; 44:e25-e31. [PMID: 30630654 DOI: 10.1016/j.meddos.2018.12.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/05/2018] [Accepted: 12/11/2018] [Indexed: 11/20/2022]
Abstract
Various dosimetric benefits such as increased dose rate, and reduced leakage and out of field dose have led to the growth of flattening-filter-free (FFF) technology in the clinic. In this study, we concentrate on investigating the feasibility of using FFF beams to deliver conventional flat beams, since completely getting rid of the flattening-filter module from the gantry head can not only simplify the gantry design but also decrease the workload on machine maintenance and quality assurance. Two intensity modulated radiotherapy techniques, step-and-shoot (S&S) and sliding window (SW), were used to generate flat beam profiles for 6 regular-shaped beams and 3 clinical beams while operating in FFF mode. The inverse plans were generated based on uniform dose optimization. Degree of flatness, MU efficiency, and beam delivery time for both methods were assessed. S&S technique is able to achieve a degree of flatness less than 2.5% for most field configurations. While SW technique was able to generate relatively flat beams for field sizes less than 18 × 18 cm2. For all field configurations, S&S beams resulted in a longer delivery time compared to reference flat beams and SW beams. For field sizes less than 18 × 18 cm2, SW modulated FFF beams resulted in a faster delivery time compared to reference flat beams. The ability to deliver conventional flat beams is not absent when operating in FFF mode. Utilizing beam modulation, FFF mode can achieve reasonable flat profiles and comparable efficiency to conventional flat beams. The ability to deliver most clinical treatments from the same treatment unit will allow for less quality assurance as well as maintenance, and completely eliminate the need for the flattening filter on modern linacs.
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Affiliation(s)
- Nicholas J Potter
- Department of Radiation Oncology, University of Florida, Gainesville, FL 32610.
| | - Sharon Lebron
- Department of Radiation Oncology, University of Florida, Gainesville, FL 32610
| | - Jonathan G Li
- Department of Radiation Oncology, University of Florida, Gainesville, FL 32610
| | - Chihray Liu
- Department of Radiation Oncology, University of Florida, Gainesville, FL 32610
| | - Bo Lu
- Department of Radiation Oncology, University of Florida, Gainesville, FL 32610
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16
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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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17
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Chow JCL, Owrangi AM. Mucosal dosimetry on unflattened photon beams: a Monte Carlo phantom study. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aaeaaa] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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18
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Mishra B, Mishra S, Selvam TP, Chavan ST, Pethe SN. Comparison of Measured and Monte Carlo Calculated Dose Distributions from Indigenously Developed 6 MV Flattening Filter Free Medical Linear Accelerator. J Med Phys 2018; 43:162-167. [PMID: 30305773 PMCID: PMC6172861 DOI: 10.4103/jmp.jmp_58_18] [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] [Indexed: 11/16/2022] Open
Abstract
Purpose: Monte Carlo simulation was carried out for a 6 MV flattening filter-free (FFF) indigenously developed linear accelerator (linac) using the BEAMnrc user-code of the EGSnrc code system. The model was benchmarked against the measurements. A Gaussian distributed electron beam of kinetic energy 6.2 MeV with full-width half maximum of 1 mm was used in this study. Methods: The simulation of indigenously developed linac unit has been carried out by using the Monte Carlo-based BEAMnrc user-code of the EGSnrc code system. Using the simulated model, depth and lateral dose profiles were studied using the DOSXYZnrc user-code. The calculated dose data were compared against the measurements using an RFA dosimertic system made by PTW, Germany (water tank MP3-M and 0.125 cm3 ion chamber). Results: The BEAMDP code was used to analyze photon fluence spectra, mean energy distribution, and electron contamination fluence spectra. Percentage depth dose (PDD) and beam profiles (along both X and Y directions) were calculated for the field sizes 5 cm × 5 cm - 25 cm × 25 cm. The dose difference between the calculated and measured PDD and profile values were under 1%, except for the penumbra region where the maximum deviation was found to be around 3%. Conclusions: A Monte Carlo model of indigenous FFF linac (6 MV) has been developed and benchmarked against the measured data.
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Affiliation(s)
- Bibekananda Mishra
- Radiological Safety Division, Atomic Energy Regulatory Board, Mumbai, Maharashtra, India.,Homi Bhabha National Institute, Health, Safety and Environment Group, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
| | - Subhalaxmi Mishra
- Homi Bhabha National Institute, Health, Safety and Environment Group, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India.,Radiological Physics and Advisory Division, Health, Safety and Environment Group, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
| | - T Palani Selvam
- Homi Bhabha National Institute, Health, Safety and Environment Group, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India.,Radiological Physics and Advisory Division, Health, Safety and Environment Group, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
| | - S T Chavan
- Medical Electronics Division-1, Society for Applied Microwave Electronics Engineering and Research, Mumbai, Maharashtra, India
| | - S N Pethe
- Medical Electronics Division-1, Society for Applied Microwave Electronics Engineering and Research, Mumbai, Maharashtra, India
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19
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Vassiliev ON, Kry SF, Wang HC, Peterson CB, Chang JY, Mohan R. Radiotherapy of lung cancers: FFF beams improve dose coverage at tumor periphery compromised by electronic disequilibrium. Phys Med Biol 2018; 63:195007. [PMID: 30189421 DOI: 10.1088/1361-6560/aadf7d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this work was to investigate radiotherapy underdosing at the periphery of lung tumors, and differences in dose for treatments delivered with flattening filter-free (FFF) beams and with conventional flattened (FF) beams. The true differences between these delivery approaches, as assessed with Monte Carlo simulations, were compared to the apparent differences seen with clinical treatment planning algorithms AAA and Acuros XB. Dose was calculated in a phantom comprised of a chest wall, lung parenchyma, and a spherical tumor (tested diameters: 1, 3, and 5 cm). Three lung densities were considered: 0.26, 0.2, and 0.1 g cm-3, representing normal lung, lung at full inspiration, and emphysematous lung, respectively. The dose was normalized to 50 Gy to the tumor center and delivered with 7 coplanar, unmodulated 6 MV FFF or FF beams. Monte Carlo calculations used EGSnrc and phase space files for the TrueBeam accelerator provided by Varian Medical Systems. Voxel sizes were 0.5 mm for the 1 cm tumor and 1 mm for the larger tumors. AAA and Acuros XB dose calculations were performed in Eclipse™ with a 2.5 mm dose grid, the resolution normally used clinically. Monte Carlo dose distributions showed that traditional FF beams underdosed the periphery of the tumor by up to ~2 Gy as compared to FFF beams; the latter provided a more uniform dose throughout the tumor. In all cases, the underdosed region was a spherical shell about 5 mm thick around the tumor and extending into the tumor by 2-3 mm. The effect was most pronounced for smaller tumors and lower lung densities. The underdosing observed with conventional FF beams was not captured by the clinical treatment planning systems. We concluded that FFF beams mitigate dose loss at tumor periphery and current clinical practice fails to capture tumor periphery underdosing and possible ways to mitigate it.
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Affiliation(s)
- Oleg N Vassiliev
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030, United States of America. Author to whom any correspondence should be addressed
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20
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Tsubouchi T, Yagi M, Sumida I, Tamari K, Seo Y, Ogawa K. The effect of beam shape on physical parameters of head and neck simultaneous-integrated boost intensity-modulated radiation therapy. Rep Pract Oncol Radiother 2018; 23:425-432. [PMID: 30197578 DOI: 10.1016/j.rpor.2018.08.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 07/18/2018] [Accepted: 08/16/2018] [Indexed: 11/29/2022] Open
Abstract
Aim To evaluate the influence of the beam shape created by X-rays with "flat beams" and without "flattening-filter-free [FFF] beams" a flattening filter, and the isocenter locations for FFF beams on the treatment of a large irradiated volume for tumours. Background The increase of dose rate and the decrease of out-of-field dose can be expected for FFF beams and lead to effective and safety radiotherapy. On the other hand, the bell-shaped dose profile is thought to be a factor of negating these advantages. Materials and methods Treatment plans for 15 patients with head and neck cancer were created using XiO (Elekta, Stockholm AB, Sweden) in fixed-gantry step-and-shoot delivery under the same dose constraints. Seven fields of FFF beams with 7 MV and flat beams with 6 MV were used with the technique of intensity-modulated radiation therapy (IMRT). We compared the dose homogeneity and conformity of targets and dose constraints for organs as the plan quality and evaluated physical parameters: monitor unit (MU) values, number of segments and their locations from the isocenter in beam's-eye-view. Results No significant differences were found in the plan quality. The isocenter locations do not affect the physical parameters for FFF beams. It has been confirmed that the number of segments and MU values were 40% higher with FFF beams than with flat beams (p < 0.05). Conclusion This study demonstrates flat dose distribution is more suitable for IMRT with large and complex targets.
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Affiliation(s)
- Toshiro Tsubouchi
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, 1, Yamadaoka, Suita-city, Osaka 565-0871, Japan
| | - Masashi Yagi
- Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, 1, Yamadaoka, Suita-city, Osaka 565-0871, Japan
| | - Iori Sumida
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, 1, Yamadaoka, Suita-city, Osaka 565-0871, Japan
| | - Keisuke Tamari
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, 1, Yamadaoka, Suita-city, Osaka 565-0871, Japan
| | - Yuji Seo
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, 1, Yamadaoka, Suita-city, Osaka 565-0871, Japan
| | - Kazuhiko Ogawa
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, 1, Yamadaoka, Suita-city, Osaka 565-0871, Japan
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de Prez L, de Pooter J, Jansen B, Perik T, Wittkämper F. Comparison of k Q factors measured with a water calorimeter in flattening filter free (FFF) and conventional flattening filter (cFF) photon beams. Phys Med Biol 2018; 63:045023. [PMID: 29461974 DOI: 10.1088/1361-6560/aaaa93] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Recently flattening filter free (FFF) beams became available for application in modern radiotherapy. There are several advantages of FFF beams over conventional flattening filtered (cFF) beams, however differences in beam spectra at the point of interest in a phantom potentially affect the ion chamber response. Beams are also non-uniform over the length of a typical reference ion chamber and recombination is usually larger. Despite several studies describing FFF beam characteristics, only a limited number of studies investigated their effect on k Q factors. Some of those studies predicted significant discrepancies in k Q factors (0.4% up to 1.0%) if TPR20,10 based codes of practice (CoPs) were to be used. This study addresses the question to which extent k Q factors, based on a TPR20,10 CoP, can be applied in clinical reference dosimetry. It is the first study that compares k Q factors measured directly with an absorbed dose to water primary standard in FFF-cFF pairs of clinical photon beams. This was done with a transportable water calorimeter described elsewhere. The measurements corrected for recombination and beam radial non-uniformity were performed in FFF-cFF beam pairs at 6 MV and 10 MV of an Elekta Versa HD for a selection of three different Farmer-type ion chambers (eight serial numbers). The ratio of measured k Q factors of the FFF-cFF beam pairs were compared with the TPR20,10 CoPs of the NCS and IAEA and the %dd(10) x CoP of the AAPM. For the TPR20,10 based CoPs differences less than 0.23% were found in k Q factors between the corresponding FFF-cFF beams with standard uncertainties smaller than 0.35%, while for the %dd(10) x these differences were smaller than 0.46% and within the expanded uncertainty of the measurements. Based on the measurements made with the equipment described in this study the authors conclude that the k Q factors provided by the NCS-18 and IAEA TRS-398 codes of practice can be applied for flattening filter free beams without additional correction. However, existing codes of practice cannot be applied ignoring the significant volume averaging effect of the FFF beams over the ion chamber cavity. For this a corresponding volume averaging correction must be applied.
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Affiliation(s)
- Leon de Prez
- VSL-Dutch Metrology Institute, Delft, Netherlands
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22
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Asadi A, Razavi-Ratki SK, Jabbari K, Najafzadeh M, Nickfarjam A. Monte Carlo evaluation of the potential benefits of flattening filter free beams from the Oncor® clinical linear accelerator. JOURNAL OF X-RAY SCIENCE AND TECHNOLOGY 2018; 26:281-302. [PMID: 29562568 DOI: 10.3233/xst-17315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
OBJECTIVES To evaluate the potential privileges of flattening filter-free (FFF) photon beams from Oncor® linac for 6 MV and 18 MV energies. METHODS A Monte Carlo (MC) model of Oncor® linac was built using BEAMnrc MCCode and verified by the measured data using 6 MV and 18 MV energies. A comprehensive set of data was also characterized for MC model of Oncor® machine running with and without flattening filter (FF) for 6 MV and 18 MV beams in six field sizes. The investigated characteristics included mean energy, energy spectrum, photon spatial fluence, superficial dose, percent depth dose (PDD), dose output, and out-of-field dose with two indexes of lateral dose profile and isodose curve at three depths. RESULTS Using FFF enhanced the energy uniformity 3.4±0.11% (6 MV) and 2.05±0.09% (18 MV) times and improved dose output by factor of 2.91 (6 MV) and 4.2 (18 MV) on the central axis, respectively. Using FFF also reduced the PDD dependencies by 9.1% (6 MV) and 5.57% (18 MV). In addition, using FFF had a lower out-of-field dose due to the reduced head scatter and softer spectra. CONCLUSIONS The findings in this study suggested that using FFF, Oncor® machine could achieve better treatment results with lower dose toxicity and a shorter beam-on time.
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Affiliation(s)
- Amin Asadi
- Medical Physics Department, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Seid Kazem Razavi-Ratki
- Radiotherapy Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
- Radiology Department, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Keyvan Jabbari
- Medical Physics Department, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Milad Najafzadeh
- Medical Physics Department, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Abolfazl Nickfarjam
- Medical Physics Department, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
- Radiotherapy Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
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23
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Xu Y, Yan H, Hu Z, Ma P, Men K, Huang P, Ren W, Dai J, Li Y. Influence of tumor location on the intensity-modulated radiation therapy plan of helical tomotherapy. Med Dosim 2017; 42:334-340. [PMID: 28797719 DOI: 10.1016/j.meddos.2017.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 04/20/2017] [Accepted: 07/03/2017] [Indexed: 11/29/2022]
Abstract
Given the design of the Helical TomoTherapy device, the patient's central axis is routinely aligned with the machine's rotational axis to prevent the patient's body from colliding with the machine walls. However, for treatment of tumors located away from the patient's central axis, this position may not be optimal as the adequate radiation dose may not reach the affected site. Our study aimed to investigate the influence of tumor location on dose quality and delivery efficiency of tomotherapy plans. A phantom and 15 patients were selected for this study. Two plans, A and B, were implemented for each case. In plan A, the patient's central axis was aligned with the machine's rotational axis, whereas in plan B, the center of the planning target volume (PTV) was aligned with the machine's rotational axis. Both plans were optimized with the same planning parameters, and the dose quality of the plans was evaluated using dosimetrics. The delivery efficiency was determined from delivery time and monitor units (MUs). A paired t-test or nonparametric Wilcoxon signed-rank test was performed for statistical comparison. In the phantom study, the median delivery times were 358 and 336 seconds for plans A and B, respectively, and this difference was significant (p = 0.005). In the patient study, the median delivery times were 348 and 317 seconds for plans A and B, respectively, and this difference was also significant (p = 0.001). The dose qualities of both plans for each patient were nearly identical. No significant differences were found in the conformal index, heterogeneity index, and mean dose delivered to normal tissue between the plans. Both phantom and patient studies showed that for normal-sized patients, the delivery time reduced as the distance between the PTV and the patient's central axis increased when the PTV center was aligned with the machine axis. In conclusion, aligning the PTV center with the machine's rotational axis by shifting the patient during tomotherapy reduces the delivery time without compromising the dose quality of intensity-modulated radiation therapy.
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Affiliation(s)
- Yingjie Xu
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing 100021, China
| | - Hui Yan
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing 100021, China
| | - Zhihui Hu
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing 100021, China
| | - Pan Ma
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing 100021, China
| | - Kuo Men
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing 100021, China
| | - Peng Huang
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing 100021, China
| | - Wenting Ren
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing 100021, China
| | - Jianrong Dai
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing 100021, China.
| | - Yexiong Li
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing 100021, China.
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Mishra B, Selvam TP, Sharma PKD. Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario. J Med Phys 2017; 42:18-24. [PMID: 28405104 PMCID: PMC5370334 DOI: 10.4103/jmp.jmp_99_16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes.
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Affiliation(s)
- Bibekananda Mishra
- Radiological Safety Division, Atomic Energy Regulatory Board, Niyamak Bhavan, Mumbai, Maharashtra, India
| | - T Palani Selvam
- Radiological Physics and Advisory Division, Health Safety and Environmental Group, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
| | - P K Dash Sharma
- Radiological Safety Division, Atomic Energy Regulatory Board, Niyamak Bhavan, Mumbai, Maharashtra, India
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25
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Covington EL, Ritter TA, Moran JM, Owrangi AM, Prisciandaro JI. Technical Report: Evaluation of peripheral dose for flattening filter free photon beams. Med Phys 2017; 43:4789. [PMID: 27487896 DOI: 10.1118/1.4958963] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To develop a comprehensive peripheral dose (PD) dataset for the two unflattened beams of nominal energy 6 and 10 MV for use in clinical care. METHODS Measurements were made in a 40 × 120 × 20 cm(3) (width × length × depth) stack of solid water using an ionization chamber at varying depths (dmax, 5, and 10 cm), field sizes (3 × 3 to 30 × 30 cm(2)), and distances from the field edge (5-40 cm). The effects of the multileaf collimator (MLC) and collimator rotation were also evaluated for a 10 × 10 cm(2) field. Using the same phantom geometry, the accuracy of the analytic anisotropic algorithm (AAA) and Acuros dose calculation algorithm was assessed and compared to the measured values. RESULTS The PDs for both the 6 flattening filter free (FFF) and 10 FFF photon beams were found to decrease with increasing distance from the radiation field edge and the decreasing field size. The measured PD was observed to be higher for the 6 FFF than for the 10 FFF for all field sizes and depths. The impact of collimator rotation was not found to be clinically significant when used in conjunction with MLCs. AAA and Acuros algorithms both underestimated the PD with average errors of -13.6% and -7.8%, respectively, for all field sizes and depths at distances of 5 and 10 cm from the field edge, but the average error was found to increase to nearly -69% at greater distances. CONCLUSIONS Given the known inaccuracies of peripheral dose calculations, this comprehensive dataset can be used to estimate the out-of-field dose to regions of interest such as organs at risk, electronic implantable devices, and a fetus. While the impact of collimator rotation was not found to significantly decrease PD when used in conjunction with MLCs, results are expected to be machine model and beam energy dependent. It is not recommended to use a treatment planning system to estimate PD due to the underestimation of the out-of-field dose and the inability to calculate dose at extended distances due to the limits of the dose calculation matrix.
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Affiliation(s)
- E L Covington
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109
| | - T A Ritter
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109 and Department of Radiation Oncology, Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, Michigan 48105
| | - J M Moran
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109
| | - A M Owrangi
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109
| | - J I Prisciandaro
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109
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Hsu SM, Hung CH, Liao YJ, Fu HM, Tsai JT, Huang YH, Huang DYC. Feasibility Study on Applying Radiophotoluminescent Glass Dosimeters for CyberKnife SRS Dose Verification. PLoS One 2017; 12:e0169252. [PMID: 28046056 PMCID: PMC5207685 DOI: 10.1371/journal.pone.0169252] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 12/14/2016] [Indexed: 11/18/2022] Open
Abstract
CyberKnife is one of multiple modalities for stereotactic radiosurgery (SRS). Due to the nature of CyberKnife and the characteristics of SRS, dose evaluation of the CyberKnife procedure is critical. A radiophotoluminescent glass dosimeter was used to verify the dose accuracy for the CyberKnife procedure and validate a viable dose verification system for CyberKnife treatment. A radiophotoluminescent glass dosimeter, thermoluminescent dosimeter, and Kodak EDR2 film were used to measure the lateral dose profile and percent depth dose of CyberKnife. A Monte Carlo simulation for dose verification was performed using BEAMnrc to verify the measured results. This study also used a radiophotoluminescent glass dosimeter coupled with an anthropomorphic phantom to evaluate the accuracy of the dose given by CyberKnife. Measurements from the radiophotoluminescent glass dosimeter were compared with the results of a thermoluminescent dosimeter and EDR2 film, and the differences found were less than 5%. The radiophotoluminescent glass dosimeter has some advantages in terms of dose measurements over CyberKnife, such as repeatability, stability, and small effective size. These advantages make radiophotoluminescent glass dosimeters a potential candidate dosimeter for the CyberKnife procedure. This study concludes that radiophotoluminescent glass dosimeters are a promising and reliable dosimeter for CyberKnife dose verification with clinically acceptable accuracy within 5%.
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Affiliation(s)
- Shih-Ming Hsu
- Medical Physics and Radiation Measurements Laboratory, Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan, ROC
- Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan, ROC
- Biophotonics and Molecular Imaging Research Center, National Yang-Ming University, Taipei, Taiwan, ROC
| | - Chao-Hsiung Hung
- Division of Radiation Therapy and Oncology, Chang Gung Memorial Hospital, Chia-Yi, Taiwan, ROC
| | - Yi-Jen Liao
- School of Medical Laboratory Science and Biotechnology, Collage of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan, ROC
| | - Hsiao-Mei Fu
- Department of radiation Oncology, MacKay Memorial Hospital, New-Taipei, Taiwan, ROC
| | - Jo-Ting Tsai
- CyberKnife Treatment Center, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan, ROC
| | - Yung-Hui Huang
- Department of Medical Imaging and Radiological Sciences, I-Shou University, Taiwan, R.O.C.
| | - David Y. C. Huang
- Medical Physics Graduate Program at Duke Kunshan University, Kunshan, Jiangsu, China
- * E-mail:
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Shimozato T, Aoyama Y, Matsunaga T, Tabushi K. Beam Characterization of 10-MV Photon Beam from Medical Linear Accelerator without Flattening Filter. J Med Phys 2017; 42:65-71. [PMID: 28706351 PMCID: PMC5496272 DOI: 10.4103/jmp.jmp_71_16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aim: This work investigated the dosimetric properties of a 10-MV photon beam emitted from a medical linear accelerator (linac) with no flattening filter (FF). The aim of this study is to analyze the radiation fluence and energy emitted from the flattening filter free (FFF) linac using Monte Carlo (MC) simulations. Materials and Methods: The FFF linac was created by removing the FF from a linac in clinical use. Measurements of the depth dose (DD) and the off-axis profile were performed using a three-dimensional water phantom with an ionization chamber. A MC simulation for a 10-MV photon beam from this FFF linac was performed using the BEAMnrc code. Results: The off-axis profiles for the FFF linac exhibited a chevron-like distribution, and the dose outside the irradiation field was found to be lower for the FFF linac than for a linac with an FF (FF linac). The DD curves for the FFF linac included many contaminant electrons in the build-up region. Conclusion: Therefore, for clinical use, a metal filter is additionally required to reduce the effects of the electron contamination. The mean energy of the FFF linac was found to be lower than that of the FF linac owing to the absence of beam hardening caused by the FF.
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Affiliation(s)
- Tomohiro Shimozato
- Department of Radiological Technology, School of Health Sciences, Gifu University of Medical Science, Seki, Gifu, Japan
| | - Yuichi Aoyama
- Department of Radiation Oncology, Kobe University Hospital, Kobe, Hyougo, Japan
| | - Takuma Matsunaga
- Department of Radiology, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka, Japan
| | - Katsuyoshi Tabushi
- Department of Radiological Technology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
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Study of unflattened photon beams shaped by multileaf collimator using BEAMnrc code. JOURNAL OF RADIOTHERAPY IN PRACTICE 2016. [DOI: 10.1017/s1460396916000340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractPurposeIn our study basic dosimetric properties of a flattening filter free 6 MV photon beam shaped by multileaf collimators (MLC) is examined using the Monte Carlo (MC) method.Methods and MaterialsBEAMnrc code was used to make a MC simulation model for 6 MV photon beam based on Varian Clinic 600 unique performance linac, operated with and without a flattening filter in beam line. Dosimetric features including central axis depth dose, beam profiles, photon and electron spectra were calculated and compared for flattened and unflattened cases.ResultsDosimetric field size and penumbra were found to be smaller for unflattened beam, and the decrease in field size was less for MLC shaped in comparison with jaw-shaped unflattened beam. Increase in dose rate of >2·4 times was observed for unflattened beam indicating a shorter beam delivery time for treatment. MLC leakage was found to decrease significantly when the flattening filter was removed from the beam line. The total scatter factor showed slower deviation with field sizes for unflattened beam indicating a reduced head scatter.ConclusionsOur study demonstrated that improved accelerator characteristics can be achieved by removing flattening filter from beam line.
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Budgell G, Brown K, Cashmore J, Duane S, Frame J, Hardy M, Paynter D, Thomas R. IPEM topical report 1: guidance on implementing flattening filter free (FFF) radiotherapy. Phys Med Biol 2016; 61:8360-8394. [DOI: 10.1088/0031-9155/61/23/8360] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Owrangi AM, Roberts DA, Covington EL, Hayman JA, Masi KM, Lee C, Moran JM, Prisciandaro JI. Revisiting fetal dose during radiation therapy: evaluating treatment techniques and a custom shield. J Appl Clin Med Phys 2016; 17:34-46. [PMID: 27685109 PMCID: PMC5874082 DOI: 10.1120/jacmp.v17i5.6135] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 03/31/2016] [Accepted: 03/28/2016] [Indexed: 11/23/2022] Open
Abstract
To create a comprehensive dataset of peripheral dose (PD) measurements from a new generation of linear accelerators with and without the presence of a newly designed fetal shield, PD measurements were performed to evaluate the effects of depth, field size, distance from the field edge, collimator angle, and beam modi-fiers for common treatment protocols and modalities. A custom fetal lead shield was designed and made for our department that allows external beam treatments from multiple angles while minimizing the need to adjust the shield during patient treatments. PD measurements were acquired for a comprehensive series of static fields on a stack of Solid Water. Additionally, PDs from various clinically relevant treatment scenarios for pregnant patients were measured using an anthropomorphic phantom that was abutted to a stack of Solid Water. As expected, the PD decreased as the distance from the field edge increased and the field size decreased. On aver-age, a PD reduction was observed when a 90° collimator rotation was applied and/or when the tertiary MLCs and jaws defined the field aperture. However, the effect of the collimator rotation (90° versus 0°) in PD reduction was not found to be clini-cally significant when the tertiary MLCs were used to define the field aperture. In the presence of both the MLCs and the fetal shield, the PD was reduced by 58% at a distance of 10 cm from the field edge. The newly designed fetal shield may effectively reduce fetal dose and is relatively easy to setup. Due to its design, we are able to use a broad range of treatment techniques and beam angles. We believe the acquired comprehensive PD dataset collected with and without the fetal shield will be useful for treatment teams to estimate fetal dose and help guide decisions on treat-ment techniques without the need to perform pretreatment phantom measurements.
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Kuess P, Georg D, Palmans H, Lechner W. Technical Note: On the impact of the incident electron beam energy on the primary dose component of flattening filter free photon beams. Med Phys 2016; 43:4507. [PMID: 27487867 DOI: 10.1118/1.4954849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE For commercially available linear accelerators (Linacs), the electron energies of flattening filter free (FFF) and flattened (FF) beams are either identical or the electron energy of the FFF beam is increased to match the percentage depth dose curve (PDD) of the FF beam (in reference geometry). This study focuses on the primary dose components of FFF beams for both kinds of settings, studied on the same Linac. METHODS The measurements were conducted on a VersaHD Linac (Elekta, Crawley, UK) for both FF and FFF beams with nominal energies of 6 and 10 MV. In the clinical setting of the VersaHD, the energy of FFFM (Matched) beams is set to match the PDDs of the FF beams. In contrast the incident electron beam of the FFFU beam was set to the same energy as for the FF beam. Half value layers (HVLs) and a dual parameter beam quality specifier (DPBQS) were determined. RESULTS For the 6 MV FFFM beam, HVL and DPBQS values were very similar compared to those of the 6 MV FF beam, while for the 10 MV FFFM and FF beams, only %dd(10)x and HVL values were comparable (differences below 1.5%). This shows that matching the PDD at one depth does not guarantee other beam quality dependent parameters to be matched. For FFFU beams, all investigated beam quality specifiers were significantly different compared to those for FF beams of the same nominal accelerator potential. The DPBQS of the 6 MV FF and FFFM beams was equal within the measurement uncertainty and was comparable to published data of a machine with similar TPR20,10 and %dd(10)x. In contrast to that, the DPBQS's two parameters of the 10 MV FFFM beam were substantially higher compared to those for the 10 MV FF beam. CONCLUSIONS PDD-matched FF and FFF beams of both nominal accelerator potentials were observed to have similar HVL values, indicating similarity of their primary dose components. Using the DPBQS revealed that the mean attenuation coefficient was found to be the same within the uncertainty of 0.8% for 6 MV FF and 6 MV FFFM beams, while for 10 MV beams, they differed by 6.4%. This shows that the DPBQS can provide a differentiation of photon beam characteristics that would remain hidden by the use of a single beam quality specifier, such as %dd(10)x or HVL.
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Affiliation(s)
- Peter Kuess
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna 1090, Austria and Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna 1090, Austria
| | - Dietmar Georg
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna 1090, Austria and Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna 1090, Austria
| | - Hugo Palmans
- EBG MedAustron GmbH, Wiener Neustadt 2700, Austria and National Physical Laboratory, Teddington TW 11 0LW, United Kingdom
| | - Wolfgang Lechner
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna 1090, Austria and Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna 1090, Austria
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Yan Y, Yadav P, Bassetti M, Du K, Saenz D, Harari P, Paliwal BR. Dosimetric differences in flattened and flattening filter-free beam treatment plans. J Med Phys 2016; 41:92-9. [PMID: 27217620 PMCID: PMC4871009 DOI: 10.4103/0971-6203.181636] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study investigated the dosimetric differences in treatment plans from flattened and flattening filter-free (FFF) beams from the TrueBeam System. A total of 104 treatment plans with static (sliding window) intensity-modulated radiotherapy beams and volumetric-modulated arc therapy (VMAT) beams were generated for 15 patients involving three cancer sites. In general, the FFF beam provides similar target coverage as the flattened beam with improved dose sparing to organ-at-risk (OAR). Among all three cancer sites, the head and neck showed more important differences between the flattened beam and FFF beam. The maximum reduction of the FFF beam in the mean dose reached up to 2.82 Gy for larynx in head and neck case. Compared to the 6 MV flattened beam, the 10 MV FFF beam provided improved dose sparing to certain OARs, especially for VMAT cases. Thus, 10 MV FFF beam could be used to improve the treatment plan.
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Affiliation(s)
- Yue Yan
- Department of Medical Physics, University of Wisconsin, Madison, USA; Department of Human Oncology, University of Wisconsin, Madison, USA
| | - Poonam Yadav
- Department of Human Oncology, University of Wisconsin, Madison, USA; Riverview Cancer Center, University of Wisconsin, Wisconsin Rapids, Wisconsin, USA
| | - Michael Bassetti
- Riverview Cancer Center, University of Wisconsin, Wisconsin Rapids, Wisconsin, USA
| | - Kaifang Du
- Riverview Cancer Center, University of Wisconsin, Wisconsin Rapids, Wisconsin, USA
| | - Daniel Saenz
- Department of Medical Physics, University of Wisconsin, Madison, USA; Department of Human Oncology, University of Wisconsin, Madison, USA
| | - Paul Harari
- Riverview Cancer Center, University of Wisconsin, Wisconsin Rapids, Wisconsin, USA
| | - Bhudatt R Paliwal
- Department of Medical Physics, University of Wisconsin, Madison, USA; Department of Human Oncology, University of Wisconsin, Madison, USA
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Meshram MN, Pramanik S, Ranjith CP, Gopal SK, Dobhal R. Dosimetric properties of equivalent-quality flattening filter-free (FFF) and flattened photon beams of Versa HD linear accelerator. J Appl Clin Med Phys 2016; 17:358-370. [PMID: 27167293 PMCID: PMC5690903 DOI: 10.1120/jacmp.v17i3.6173] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 01/18/2016] [Accepted: 01/12/2016] [Indexed: 11/23/2022] Open
Abstract
This study presents the basic dosimetric properties of photon beams of a Versa HD linear accelerator (linac), which is capable of delivering flattening filter‐free (FFF) beams with a beam quality equivalent to the corresponding flattened beams based on comprehensive beam data measurement. The analyzed data included the PDDs, profiles, penumbra, out‐of‐field doses, surface doses, output factors, head and phantom scatter factors, and MLC transmissions for both FFF and flattened beams of 6 MV and 10 MV energy from an Elekta Versa HD linac. The 6MVFFF and 10MVFFF beams had an equivalent mean energy to the flattened beams and showed less PDD variations with the field sizes. Compared with their corresponding flattened beams, Dmax was deeper for FFF beams for all field sizes; the ionization ratio variations with the field size were lower for FFF beams; the out‐of‐field doses were lower and the penumbras were sharper for the FFF beams; the off‐axis profile variations with the depths were lesser for the FFF beams. Further, the 6MVFFF and 10MVFFF beams had 35.7% and 40.9% less variations in output factor with the field size, respectively. The collimator exchange effect was reduced in the FFF mode. The head scatter factor showed 59.1% and 73.6% less variations, on average, for the 6MVFFF and 10MVFFF beams, respectively; the variations in the phantom scatter factor were also smaller. The surface doses for all beams increased linearly with the field size. The 6MVFFF and 10MVFFF beams had higher surface doses than the corresponding flattened beams for field sizes of up to 10×10cm2 but had lower surface doses for larger fields. Both FFF beams had lower average MLC transmissions than the flattened beams. The finding that the FFF beams were of equivalent quality to the corresponding flattened beams indicates a significant difference from the data on unmatched FFF beams. PACS number(s): 87.56.bd, 87.55.Qr
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Saenz DL, Narayanasamy G, Cruz W, Papanikolaou N, Stathakis S. Pinnacle3 modeling and end-to-end dosimetric testing of a Versa HD linear accelerator with the Agility head and flattening filter-free modes. J Appl Clin Med Phys 2016; 17:192-206. [PMID: 26894352 PMCID: PMC5690210 DOI: 10.1120/jacmp.v17i1.5808] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 08/27/2015] [Accepted: 08/26/2015] [Indexed: 11/23/2022] Open
Abstract
The Elekta Versa HD incorporates a variety of upgrades to the line of Elekta linear accelerators, primarily including the Agility head and flattening filter‐free (FFF) photon beam delivery. The completely distinct dosimetric output of the head from its predecessors, combined with the FFF beams, requires a new investigation of modeling in treatment planning systems. A model was created in Pinnacle3 v9.8 with the commissioned beam data. A phantom consisting of several plastic water and Styrofoam slabs was scanned and imported into Pinnacle3, where beams of different field sizes, source‐to‐surface distances (SSDs), wedges, and gantry angles were devised. Beams included all of the available photon energies (6, 10, 18, 6 FFF, and 10 FFF MV), as well as the four electron energies commissioned for clinical use (6, 9, 12, and 15 MeV). The plans were verified at calculation points by measurement with a calibrated ionization chamber. Homogeneous and heterogeneous point‐dose measurements agreed within 2% relative to maximum dose for all photon and electron beams. AP photon open field measurements along the central axis at 100 cm SSD passed within 1%. In addition, IMRT testing was also performed with three standard plans (step and shoot IMRT, as well as a small‐ and large‐field VMAT plan). The IMRT plans were delivered on the Delta4 IMRT QA phantom, for which a gamma passing rate was >99.5% for all plans with a 3% dose deviation, 3 mm distance‐to‐agreement, and 10% dose threshold. The IMRT QA results for the first 23 patients yielded gamma passing rates of 97.4%±2.3%. Such testing ensures confidence in the ability of Pinnacle3 to model photon and electron beams with the Agility head. PACS numbers: 87.55.D, 87.56.bd
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Affiliation(s)
- Daniel L Saenz
- University of Texas Health Science Center - San Antonio.
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Chow JCL, Owrangi AM. A surface energy spectral study on the bone heterogeneity and beam obliquity using the flattened and unflattened photon beams. Rep Pract Oncol Radiother 2015; 21:63-70. [PMID: 26900360 DOI: 10.1016/j.rpor.2015.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 09/30/2015] [Accepted: 11/05/2015] [Indexed: 11/28/2022] Open
Abstract
AIM Using flattened and unflattened photon beams, this study investigated the spectral variations of surface photon energy and energy fluence in the bone heterogeneity and beam obliquity. BACKGROUND Surface dose enhancement is a dosimetric concern when using unflattened photon beam in radiotherapy. It is because the unflattened photon beam contains more low-energy photons which are removed by the flattening filter of the flattened photon beam. MATERIALS AND METHODS We used a water and bone heterogeneity phantom to study the distributions of energy, energy fluence and mean energy of the 6 MV flattened and unflattened photon beams (field size = 10 cm × 10 cm) produced by a Varian TrueBEAM linear accelerator. These elements were calculated at the phantom surfaces using Monte Carlo simulations. The photon energy and energy fluence calculations were repeated with the beam angle turned from 0° to 15°, 30° and 45° in the water and bone phantom. RESULTS Spectral results at the phantom surfaces showed that the unflattened photon beams contained more photons concentrated mainly in the low-energy range (0-2 MeV) than the flattened beams associated with a flattening filter. With a bone layer of 1 cm under the phantom surface and within the build-up region of the 6 MV photon beam, it is found that both the flattened and unflattened beams had slightly less photons in the energy range <0.4 MeV compared to the water phantom. This shows that the presence of the bone decreased the low-energy photon backscatters to the phantom surface. When both the flattened and unflattened photon beams were rotated from 0° to 45°, the number of photon and mean photon energy increased. This indicates that both photon beams became more hardened or penetrate when the beam angle increased. In the presence of bone, the mean energies of both photon beams increased. This is due to the absorption of low-energy photons by the bone, resulting in more beam hardening. CONCLUSIONS This study explores the spectral relationships of surface photon energy and energy fluence with bone heterogeneity and beam obliquity for the flattened and unflattened photon beams. The photon spectral information is important in studies on the patient's surface dose enhancement using unflattened photon beams in radiotherapy.
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Affiliation(s)
- James C L Chow
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5G 2M9, Canada; Radiation Medicine Program, Princess Margaret Caner Center, University Health Network, Toronto, ON M5G 2M9, Canada
| | - Amir M Owrangi
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5G 2M9, Canada; Department of Medical Physics, Sunnybrook Health Sciences Center, Toronto ON M4N 3M5, Canada
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A comparison between direct TMR measurements and TMRs calculated from PDDs using BJR Supplement 25 data for flattened and unflattened photon beams. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2015; 38:503-7. [DOI: 10.1007/s13246-015-0359-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 06/23/2015] [Indexed: 10/23/2022]
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Xiao Y, Kry SF, Popple R, Yorke E, Papanikolaou N, Stathakis S, Xia P, Huq S, Bayouth J, Galvin J, Yin FF. Flattening filter-free accelerators: a report from the AAPM Therapy Emerging Technology Assessment Work Group. J Appl Clin Med Phys 2015; 16:5219. [PMID: 26103482 PMCID: PMC5690108 DOI: 10.1120/jacmp.v16i3.5219] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Revised: 02/06/2015] [Accepted: 01/23/2015] [Indexed: 11/23/2022] Open
Abstract
This report describes the current state of flattening filter‐free (FFF) radiotherapy beams implemented on conventional linear accelerators, and is aimed primarily at practicing medical physicists. The Therapy Emerging Technology Assessment Work Group of the American Association of Physicists in Medicine (AAPM) formed a writing group to assess FFF technology. The published literature on FFF technology was reviewed, along with technical specifications provided by vendors. Based on this information, supplemented by the clinical experience of the group members, consensus guidelines and recommendations for implementation of FFF technology were developed. Areas in need of further investigation were identified. Removing the flattening filter increases beam intensity, especially near the central axis. Increased intensity reduces treatment time, especially for high‐dose stereotactic radiotherapy/radiosurgery (SRT/SRS). Furthermore, removing the flattening filter reduces out‐of‐field dose and improves beam modeling accuracy. FFF beams are advantageous for small field (e.g., SRS) treatments and are appropriate for intensity‐modulated radiotherapy (IMRT). For conventional 3D radiotherapy of large targets, FFF beams may be disadvantageous compared to flattened beams because of the heterogeneity of FFF beam across the target (unless modulation is employed). For any application, the nonflat beam characteristics and substantially higher dose rates require consideration during the commissioning and quality assurance processes relative to flattened beams, and the appropriate clinical use of the technology needs to be identified. Consideration also needs to be given to these unique characteristics when undertaking facility planning. Several areas still warrant further research and development. Recommendations pertinent to FFF technology, including acceptance testing, commissioning, quality assurance, radiation safety, and facility planning, are presented. Examples of clinical applications are provided. Several of the areas in which future research and development are needed are also indicated. PACS number: 87.53.‐j, 87.53.Bn, 87.53.Ly, 87.55.‐x, 87.55.N‐, 87.56.bc
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Affiliation(s)
- Ying Xiao
- Thomas Jefferson University Hospital.
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Impact of flattening-filter-free radiation on the clonogenic survival of astrocytic cell lines. Strahlenther Onkol 2015; 191:590-6. [DOI: 10.1007/s00066-015-0823-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 01/28/2015] [Indexed: 11/25/2022]
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Abstract
In radiation therapy, unlike most other applications involving radiation, the intention is to deliver high doses of radiation to diseased tissue, constrained by the effects of radiation to healthy tissue. With regard to patient exposure, the radiation protection framework of justification, optimization, and limitation is a direct part of the prescription process of radiation therapy. Staff and public exposures are typically far below occupational maximum permissible exposures. However, a number of other issues arise in radiation therapy that fall into the category of radiation protection. After an historical review, this paper discusses several contemporary and emerging concerns within radiation therapy, including fetal dose, secondary malignancies, and dose to implantable devices, all of which involve accurate dose assessment outside the intended treatment volume. Other concerns include quality and safety, molecularly based disease assessment and treatment, and other novel treatment strategies. The paper ends with a discussion of the interplay between best practices and regulatory oversight.
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Affiliation(s)
- Steven G Sutlief
- * Professor, Division of Medical Physics and Technology, Department of Radiation Medicine & Applied Sciences, University of California, San Diego, 3855 Health Sciences Dr. #0843, La Jolla, CA 92093-0843
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Sahani G, Sharma SD, Sharma PKD, Deshpande DD, Negi PS, Sathianarayanan VK, Rath GK. Acceptance criteria for flattening filter-free photon beam from standard medical electron linear accelerator: AERB task group recommendations. J Med Phys 2014; 39:206-11. [PMID: 25525307 PMCID: PMC4258727 DOI: 10.4103/0971-6203.144482] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Revised: 09/25/2014] [Accepted: 09/29/2014] [Indexed: 11/13/2022] Open
Abstract
Medical electron linear accelerators with the capability of generating unflat photon (flattening filter-free, FFF) beams are also available commercially for clinical applications in radiotherapy. However, the beam characteristics evaluation criteria and parameters are not yet available for such photon beams. Atomic Energy Regulatory Board (AERB) of India constituted a Task Group comprising experts from regulatory agency, advisory body/research and technical institutions, and clinical radiotherapy centers in the country to evolve and recommend the acceptance criteria for the flattening filter-free (FFF) photon beams. The Task Group thoroughly reviewed the literature and inputs of the manufactures/suppliers of the FFF linac and recommended a set of dosimetry parameters for evaluating the characteristics of the unflat photon beam. The recommendations included the evaluation of quality index, degree of unflatness, difference in percentage surface dose between flat and unflat photon beams, percentage depth dose at 10 cm depth, off-axis-ratios and radiation beam penumbra. The recommended parameters were evaluated for FFF photon beams generated by three different models of the linac, and it was observed that recommended evaluation methods are simple and easy to be implemented with the existing dosimetry and quality assurance infrastructure of the linac facilities of the radiotherapy departments. Recommendations were also made for periodic quality control check of the unflat photon beams and constancy evaluation in the beam characteristics.
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Affiliation(s)
- G Sahani
- Radiological Safety Division, Atomic Energy Regulatory Board, Niyamak Bhavan, Mumbai, India
| | - S D Sharma
- Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, CTCRS, Mumbai, India
| | - P K Dash Sharma
- Radiological Safety Division, Atomic Energy Regulatory Board, Niyamak Bhavan, Mumbai, India
| | - D D Deshpande
- Department of Medical Physics, Tata Memorial Hospital, Mumbai, India
| | - P S Negi
- Department of Medical Physics, Delhi State Cancer Institute, New Delhi, India
| | | | - G K Rath
- Dr. B. R. Ambedkar Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India
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Wen N, Zhao B, Kim J, Chin-Snyder K, Bellon M, Glide-Hurst C, Barton K, Chen D, Chetty IJ. IMRT and RapidArc commissioning of a TrueBeam linear accelerator using TG-119 protocol cases. J Appl Clin Med Phys 2014; 15:4843. [PMID: 25207569 PMCID: PMC5711094 DOI: 10.1120/jacmp.v15i5.4843] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 06/11/2014] [Accepted: 06/04/2014] [Indexed: 12/03/2022] Open
Abstract
The purpose of this study is to evaluate the overall accuracy of intensity‐modulated radiation therapy (IMRT) and RapidArc delivery using both flattening filter (FF) and flattening filter‐free (FFF) modalities based on test cases developed by AAPM Task Group 119. Institutional confidence limits (CLs) were established as the baseline for patient specific treatment plan quality assurance (QA). The effects of gantry range, gantry speed, leaf speed, dose rate, as well as the capability to capture intentional errors, were evaluated by measuring a series of Picket Fence (PF) tests using the electronic portal imaging device (EPID) and EBT3 films. Both IMRT and RapidArc plans were created in a Solid Water phantom (30 × 30 × 15 cm3) for the TG‐119 test cases representative of normal clinical treatment sites for all five photon energies (6X, 10X, 15X, 6X‐FFF, 10X‐FFF) and the Exact IGRT couch was included in the dose calculation. One high‐dose point in the PTV and one low‐dose point in the avoidance structure were measured with an ion chamber in each case for each energy. Similarly, two GAFCHROMIC EBT3 films were placed in the coronal planes to measure planar dose distributions in both high‐ and low‐dose regions. The confidence limit was set to have 95% of the measured data fall within the tolerance. The mean of the absolute dose deviation for variable dose rate and gantry speed during RapidArc delivery was within 0.5% for all energies. The corresponding results for leaf speed tests were all within 0.4%. The combinations of dynamic leaf gap (DLG) and MLC transmission factor were optimized based on the ion chamber measurement results of RapidArc delivery for each energy. The average 95% CLs for the high‐dose point in the PTV were 0.030 ± 0.007 (range, 0.022–0.038) for the IMRT plans and 0.029 ± 0.011 (range, 0.016–0.043) for the RapidArc plans. For low‐point dose in the avoidance structures, the CLs were 0.029 ± 0.006 (range, 0.024–0.039) for the IMRT plans and 0.027 ± 0.013 (range, 0.017–0.047) for the RapidArc plans. The average 95% CLs using 3%/3 mm gamma criteria in the high‐dose region were 5.9 ± 2.7 (range, 1.4–8.6) and 3.9 ± 2.9 (range, 1.5–8.8) for IMRT and RapidArc plans, respectively. The average 95% CLs in the low‐dose region were 5.3 ± 2.6 (range, 1.2–7.4) and 3.7 ± 2.8 (range, 1.8–8.3) for IMRT and RapidArc plans, respectively. Based on ion chamber, as well as film measurements, we have established CLs values to ensure the high precision of IMRT and RapidArc delivery for both FF and FFF modalities. PACS number: 87
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Huang JY, Eklund D, Childress NL, Howell RM, Mirkovic D, Followill DS, Kry SF. Investigation of various energy deposition kernel refinements for the convolution∕superposition method. Med Phys 2014; 40:121721. [PMID: 24320507 DOI: 10.1118/1.4831758] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Several simplifications used in clinical implementations of the convolution∕superposition (C∕S) method, specifically, density scaling of water kernels for heterogeneous media and use of a single polyenergetic kernel, lead to dose calculation inaccuracies. Although these weaknesses of the C∕S method are known, it is not well known which of these simplifications has the largest effect on dose calculation accuracy in clinical situations. The purpose of this study was to generate and characterize high-resolution, polyenergetic, and material-specific energy deposition kernels (EDKs), as well as to investigate the dosimetric impact of implementing spatially variant polyenergetic and material-specific kernels in a collapsed cone C∕S algorithm. METHODS High-resolution, monoenergetic water EDKs and various material-specific EDKs were simulated using the EGSnrc Monte Carlo code. Polyenergetic kernels, reflecting the primary spectrum of a clinical 6 MV photon beam at different locations in a water phantom, were calculated for different depths, field sizes, and off-axis distances. To investigate the dosimetric impact of implementing spatially variant polyenergetic kernels, depth dose curves in water were calculated using two different implementations of the collapsed cone C∕S method. The first method uses a single polyenergetic kernel, while the second method fully takes into account spectral changes in the convolution calculation. To investigate the dosimetric impact of implementing material-specific kernels, depth dose curves were calculated for a simplified titanium implant geometry using both a traditional C∕S implementation that performs density scaling of water kernels and a novel implementation using material-specific kernels. RESULTS For our high-resolution kernels, we found good agreement with the Mackie et al. kernels, with some differences near the interaction site for low photon energies (<500 keV). For our spatially variant polyenergetic kernels, we found that depth was the most dominant factor affecting the pattern of energy deposition; however, the effects of field size and off-axis distance were not negligible. For the material-specific kernels, we found that as the density of the material increased, more energy was deposited laterally by charged particles, as opposed to in the forward direction. Thus, density scaling of water kernels becomes a worse approximation as the density and the effective atomic number of the material differ more from water. Implementation of spatially variant, polyenergetic kernels increased the percent depth dose value at 25 cm depth by 2.1%-5.8% depending on the field size, while implementation of titanium kernels gave 4.9% higher dose upstream of the metal cavity (i.e., higher backscatter dose) and 8.2% lower dose downstream of the cavity. CONCLUSIONS Of the various kernel refinements investigated, inclusion of depth-dependent and metal-specific kernels into the C∕S method has the greatest potential to improve dose calculation accuracy. Implementation of spatially variant polyenergetic kernels resulted in a harder depth dose curve and thus has the potential to affect beam modeling parameters obtained in the commissioning process. For metal implants, the C∕S algorithms generally underestimate the dose upstream and overestimate the dose downstream of the implant. Implementation of a metal-specific kernel mitigated both of these errors.
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Affiliation(s)
- Jessie Y Huang
- The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas 77030 and Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030
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Chow JC, Owrangi AM. Dosimetric dependences of bone heterogeneity and beam angle on the unflattened and flattened photon beams: A Monte Carlo comparison. Radiat Phys Chem Oxf Engl 1993 2014. [DOI: 10.1016/j.radphyschem.2014.03.041] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Javedan K, Feygelman V, Zhang RR, Moros EG, Correa CR, Trotti A, Li W, Zhang GG. Monte Carlo comparison of superficial dose between flattening filter free and flattened beams. Phys Med 2014; 30:503-8. [PMID: 24662096 DOI: 10.1016/j.ejmp.2014.03.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 01/27/2014] [Accepted: 03/03/2014] [Indexed: 10/25/2022] Open
Abstract
This study investigates the superficial dose from FFF beams in comparison with the conventional flattened ones using a Monte Carlo (MC) method. Published phase-space files which incorporated real geometry of a TrueBeam accelerator were used for the dose calculation in phantom and clinical cases. The photon fluence on the central axis is 3 times that of a flattened beam for a 6 MV FFF beam and 5 times for a 10 MV beam. The mean energy across the field in air at the phantom surface is 0.92-0.95 MeV for the 6 MV FFF beam and 1.18-1.30 MeV for the corresponding flattened beam. At 10 MV, the values are 1.52-1.72 and 2.15-2.87 MeV for the FFF and flattened beams, respectively. The phantom dose at the depth of 1 mm in the 6 MV FFF beam is 6% ± 2.5% (of the maximum dose) higher compared to the flattened beam for a 25 × 25 cm(2) field and 14.6% ± 1.9% for the 2 × 2 cm(2) field. For the 10 MV beam, the corresponding differences are 3.4% ± 1.5% and 10.7% ± 0.6%. The skin dose difference at selected points on the patient's surface between the plans using FFF and flattened beams in the head-and-neck case was 6.5% ± 2.3% (1SD), and for the breast case it was 6.4% ± 2.3%. The Monte Carlo simulations showed that due to the lower mean energy in the FFF beam, the clinical superficial dose is higher without the flattening filter compared to the flattened beam.
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Affiliation(s)
- Khosrow Javedan
- Radiation Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
| | | | - Ray R Zhang
- School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
| | - Eduardo G Moros
- Radiation Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
| | - Candace R Correa
- Radiation Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
| | - Andy Trotti
- Radiation Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
| | - Weiqi Li
- Radiation Oncology Department, Moffitt Cancer Center, Tampa, FL, USA
| | - Geoffrey G Zhang
- Radiation Oncology Department, Moffitt Cancer Center, Tampa, FL, USA.
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Foster RD, Speiser MP, Solberg TD. Commissioning and verification of the collapsed cone convolution superposition algorithm for SBRT delivery using flattening filter-free beams. J Appl Clin Med Phys 2014; 15:4631. [PMID: 24710452 PMCID: PMC5875462 DOI: 10.1120/jacmp.v15i2.4631] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 10/22/2013] [Accepted: 10/22/2013] [Indexed: 11/25/2022] Open
Abstract
Linacs equipped with flattening filter‐free (FFF) megavoltage photon beams are now commercially available. However, the commissioning of FFF beams poses challenges that are not shared with traditional flattened megavoltage X‐ray beams. The planning system must model a beam that is peaked in the center and has an energy spectrum that is softer than the flattened beam. Removing the flattening filter also increases the maximum possible dose rates from 600 MU/min up to 2400 MU/min in some cases; this increase in dose rate affects the recombination correction factor, Pion, used during absolute dose calibration with ionization chambers. We present the first‐reported experience of commissioning, verification, and clinical use of the collapsed cone convolution superposition (CCCS) dose calculation algorithm for commercially available flattening filter‐free beams. Our commissioning data are compared to previously reported measurements and Monte Carlo studies of FFF beams. Commissioning was verified by making point‐dose measurement of test plans, irradiating the RPC lung phantom, and performing patient‐specific QA. The average point‐dose difference between calculations and measurements of all test plans and all patient specific QA measurements is 0.80%, and the RPC phantom absolute dose differences for the two thermoluminescent dosimeters (TLDs) in the phantom planning target volume (PTV) were 1% and 2%, respectively. One hundred percent (100%) of points in the RPC phantom films passed the RPC gamma criteria of 5% and 5 mm. Our results show that the CCCS algorithm can accurately model FFF beams and calculate SBRT dose distributions using those beams. PACS number: 87.55.kh
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Chung H, Prado KL, Yi BY. An analytical formalism to calculate phantom scatter factors for flattening filter free (FFF) mode photon beams. Phys Med Biol 2014; 59:951-60. [PMID: 24503449 DOI: 10.1088/0031-9155/59/4/951] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Phantom Scatter Factors, Sp in the Khan formalism (Khan et al 1980 J. Radiat. Oncol. Biol. Phys. 6 745-51) describe medium-induced changes in photon-beam intensity as a function of size of the beam. According to the British Journal of Radiology, Supplement 25, megavoltage phantom scatter factors are invariant as a function of photon-beam energy. However, during the commissioning of an accelerator with flattening filter free (FFF) photon beams (Varian TrueBeam(TM) 6-MV FFF and 10-MV FFF), differences were noted in phantom scatter between the filtered beams and FFF-mode beams. The purpose of this work was to evaluate this difference and provide an analytical formalism to explain the phantom scatter differences between FFF-mode and the filtered mode. An analytical formalism was devised to demonstrate the source of phantom scatter differences between the filtered and the FFF-mode beams. The reason for the differences in the phantom scatter factors between the filtered and the FFF-mode beams is hypothesized to be the non-uniform beam profiles of the FFF-mode beams. The analytical formalism proposed here is based on this idea, taking the product of the filtered phantom scatter factors and the ratio of the off-axis ratio between the FFF-mode and the filtered beams. All measurements were performed using a Varian TrueBeam(TM) linear accelerator with photon energies of 6-MV and 10-MV in both filtered and FFF-modes. For all measurements, a PTW Farmer type chamber and a Scanditronix CC04 cylindrical ionization were used. The in-water measurements were made at depth dose maximum and 100 cm source-to-axis distance. The in-air measurements were done at 100 cm source-to-axis distance with appropriate build-up cap. From these measurements, the phantom scatter factors were derived for the filtered beams and the FFF-mode beams for both energies to be evaluated against the phantoms scatter factors calculated using the proposed algorithm. For 6-MV, the difference between the measured and the calculated FFF-mode phantom scatter factors ranged from -0.34% to 0.73%. The average per cent difference was -0.17% (1σ = 0.25%). For 10-MV, the difference ranged from -0.19% to 0.24%. The average per cent difference was -0.17% (1σ = 0.13%). An analytical formalism was presented to calculate the phantom scatter factors for FFF-mode beams using filtered phantom scatter factors as a basis. The overall differences between measurements and calculations were within ± 0.5% for 6-MV and ± 0.25% for 10-MV.
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Affiliation(s)
- Heeteak Chung
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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Improvement of the penumbra for small radiosurgical fields using flattening filter free low megavoltage beams. Z Med Phys 2013; 23:291-9. [DOI: 10.1016/j.zemedi.2013.03.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 03/12/2013] [Accepted: 03/18/2013] [Indexed: 11/21/2022]
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Wiant DB, Terrell JA, Maurer JM, Yount CL, Sintay BJ. Commissioning and validation of BrainLAB cones for 6X FFF and 10X FFF beams on a Varian TrueBeam STx. J Appl Clin Med Phys 2013; 14:4493. [PMID: 24257290 PMCID: PMC5714633 DOI: 10.1120/jacmp.v14i6.4493] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 07/15/2013] [Accepted: 07/08/2013] [Indexed: 11/23/2022] Open
Abstract
Small field dosimetry is a challenging task. The difficulties of small field measurements, particularly stereotactic field size measurements, are highlighted by the large interinstitution variability that can be observed for circular cone collimator commissioning measurements. We believe the best way to improve the consistency of small field measurements is to clearly document and share the results of small field measurements. In this work we report on the commissioning and validation of a BrainLAB cone system for 6 MV and 10 MV flattening filter‐free (FFF) beams on a Varian TrueBeam STx. Commissioning measurements consisted of output factors, percent depth dose, and off‐axis factor measurements with a diode. Validation measurements were made in a polystyrene slab phantom at depths of 5 cm, 10 cm, and 15 cm using radiochromic film. Output factors for the 6xFFF cones are 0.689, 0. 790, 0.830, 0.871, 0.890, and 0.901 for 4 mm, 6 mm, 7.5 mm, 10 mm, 12.5 mm, and the 15 mm cones, respectively. Output factors for the 10xFFF cones are 0.566, 0. 699, 0.756, 0.826, 0.864, and 0.888 for 4 mm, 6 mm, 7.5 mm, 10 mm, 12.5 mm, and the 15 mm cones, respectively. The full width half maximum values of the off‐axis factors agreed with the nominal cone size to within 0.5 mm. Validation measurements showed an agreement of absolute dose between calculation and plan of ≤ 3.6%, and an agreement of field sizes of ≤ 0.3 mm in all cases. Radiochromic film validation measurements show reasonable agreement with beam models for circular collimators based on diode commissioning measurements. PACS numbers: 87.53.Ly, 87.53.Bn, 87.56.nk, 87.55.D‐, 87.55.km
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Zavgorodni S. Monte Carlo investigation into feasibility and dosimetry of flat flattening filter free beams. Phys Med Biol 2013; 58:7699-713. [PMID: 24140752 DOI: 10.1088/0031-9155/58/21/7699] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Flattening filter free (FFF) beams due to their non-uniformity, are sub-optimal for larger field sizes. The purpose of this study was to investigate the incident electron beam distributions that would produce flat FFF (F4) beams without the use of a flattening filter (FF). Monte Carlo (MC) simulations with BEAMnrc and DOSXYZnrc codes have been performed to evaluate feasibility of this approach. The dose distributions in water for open 6 MV beams were simulated using the Varian 21EX linac head model, which will be called the FF model. The FF was then removed from the FF model, and MC simulations were performed using (1) 6 MeV electrons incident on the target and (2) a 6 MeV electron beam with electron angular distributions optimized to provide as flat dose profiles as possible. Configuration (1) represents FFF beam while configuration (2) allowed producing a F4 beam. Optimizations have also been performed to produce flattest profiles for a set of dose rates (DRs) in the range from 1.25 to 2.4 of the DR of FF beam. Profiles and percentage depth doses (PDDs) from 6 MV F4 beams have been calculated and compared to those from the FF beam. Calculated profiles demonstrated improved flatness of the FFF beams. In fact, up to field sizes within the circle of 35 cm diameter the flatness of F4 beam at dmax was better or comparable to that of FF beam. At 20 cm off-axis the dose increased from 52% for FFF to 92% for F4 beam. Also, profiles of F4 beams did not change considerably with depth. PDDs from F4 beams were similar to those of the FFF beam. The DR for the largest modeled (44 cm diameter) F4 beam was higher than the DR from FF beam by a factor of 1.25. It was shown that the DR can be increased while maintaining beam flatness, but at the cost of reduced field size.
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Affiliation(s)
- Sergei Zavgorodni
- Department of Medical Physics, BC Cancer Agency--Vancouver Island Centre, Vancouver, BC, Canada. Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada
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Gete E, Duzenli C, Milette MP, Mestrovic A, Hyde D, Bergman AM, Teke T. A Monte Carlo approach to validation of FFF VMAT treatment plans for the TrueBeam linac. Med Phys 2013; 40:021707. [PMID: 23387730 DOI: 10.1118/1.4773883] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To commission and benchmark a vendor-supplied (Varian Medical Systems) Monte Carlo phase-space data for the 6 MV flattening filter free (FFF) energy mode on a TrueBeam linear accelerator for the purpose of quality assurance of clinical volumetric modulated arc therapy (VMAT) treatment plans. A method for rendering the phase-space data compatible with BEAMnrc/DOSXYZnrc simulation software package is presented. METHODS Monte Carlo (MC) simulations were performed to benchmark the TrueBeam 6 MV FFF phase space data that have been released by the Varian MC Research team. The simulations to benchmark the phase space data were done in three steps. First, the original phase space which was created on a cylindrical surface was converted into a format that was compatible with BEAMnrc. Second, BEAMnrc was used to create field size specific phase spaces located underneath the jaws. Third, doses were calculated with DOSXYZnrc in a water phantom for fields ranging from 1 × 1 to 40 × 40 cm(2). Calculated percent depth doses (PDD), transverse profiles, and output factors were compared with measurements for all the fields simulated. After completing the benchmarking study, three stereotactic body radiotherapy (SBRT) VMAT plans created with the Eclipse treatment planning system (TPS) were calculated with Monte Carlo. Ion chamber and film measurements were also performed on these plans. 3D gamma analysis was used to compare Monte Carlo calculation with TPS calculations and with film measurement. RESULTS For the benchmarking study, MC calculated and measured values agreed within 1% and 1.5% for PDDs and in-field transverse profiles, respectively, for field sizes >1 × 1 cm(2). Agreements in the 80%-20% penumbra widths were better than 2 mm for all the fields that were compared. With the exception of the 1 × 1 cm(2) field, the agreement between measured and calculated output factors was within 1%. It is of note that excellent agreement in output factors for all field sizes including highly asymmetric fields was achieved without accounting for backscatter into the beam monitor chamber. For the SBRT VMAT plans, the agreement between Monte Carlo and ion chamber point dose measurements was within 1%. Excellent agreement between Monte Carlo, treatment planning system and Gafchromic film dose distribution was observed with over 99% of the points in the high dose volume passing the 3%, 3 mm gamma test. CONCLUSIONS The authors have presented a method for making the Varian IAEA compliant 6 MV FFF phase space file of the TrueBeam linac compatible with BEAMnrc/DOSXYZnrc. After benchmarking the modified phase space against measurement, they have demonstrated its potential for use in MC based quality assurance of complex delivery techniques.
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Affiliation(s)
- Ermias Gete
- Medical Physics, BC Cancer Agency, Vancouver Centre, Vancouver, British Columbia, Canada
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