1
|
Haghparast M, Parwaie W, Bakhshandeh M, Tuncel N, Rabi Mahdavi S. Evaluation of Perkin Elmer Amorphous Silicon Electronic Portal Imaging Device for Small Photon Field Dosimetry. J Biomed Phys Eng 2024; 14:347-356. [PMID: 39175562 PMCID: PMC11336047 DOI: 10.31661/jbpe.v0i0.2112-1445] [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: 12/26/2021] [Accepted: 01/29/2022] [Indexed: 08/24/2024]
Abstract
Background Electronic portal imaging devices (EPIDs) are applied to measure the dose and verify patients' position. Objective The present study aims to evaluate the performance of EPID for measuring dosimetric parameters in small photon fields. Material and Methods In this experimental study, the output factors and beam profiles were obtained using the amorphous silicon (a-Si) EPID for square field sizes ranging from 1×1 to 10×10 cm2 at energies 6 and 18 mega-voltage (MV). For comparison, the dosimetric parameters were measured with the pinpoint, diode, and Semiflex dosimeters. Additionally, the Monaco treatment planning system was selected to calculate the output factors and beam profiles. Results There was a significant difference between the output factors measured using the EPID and that measured with the other dosimeters for field sizes lower than 8×8 cm2. In the energy of 6 MV, the gamma passing rates (3%/3 mm) between EPID and diode profile were 98%, 98%, 95%, 94%, 93%, and 94% for 1×1, 2×2, 3×3, 4×4, 5×5, and 10×10 cm2, respectively. The measured penumbra width with EPID was higher compared to that measured by the diode dosimeter for both energies. Conclusion The EPID can measure the dosimetric parameters in small photon fields, especially for beam profiles and penumbra measurements.
Collapse
Affiliation(s)
- Mohammad Haghparast
- Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
- Department of Radiology, Faculty of Para-Medicine, Hormozgan University of Medical Sciences, Bandare-Abbas, Iran
| | - Wrya Parwaie
- Department of Medical Physics, Faculty of Paramedical Sciences, Ilam University of Medical Sciences, Ilam, Iran
| | - Mohsen Bakhshandeh
- Department of Radiology Technology, School of Allied Medical Sciences, Shahid Beheshti University of Medical Science, Tehran, Iran
| | - Nina Tuncel
- Radiation Oncology Department, School of Medicine, Akdeniz University, Antalya, Turkey
| | - Seied Rabi Mahdavi
- Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| |
Collapse
|
2
|
Small field output factor measurement and verification for CyberKnife robotic radiotherapy and radiosurgery system using 3D polymer gel, ionization chamber, diode, diamond and scintillator detectors, Gafchromic film and Monte Carlo simulation. Appl Radiat Isot 2023; 192:110576. [PMID: 36473319 DOI: 10.1016/j.apradiso.2022.110576] [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: 08/22/2022] [Revised: 11/19/2022] [Accepted: 11/21/2022] [Indexed: 11/24/2022]
Abstract
The dosimetry of small fields has become tremendously important with the advent of intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery, where small field segments or very small fields are used to treat tumors. With high dose gradients in the stereotactic radiosurgery or radiotherapy treatment, small field dosimetry becomes challenging due to the lack of lateral electronic equilibrium in the field, x-ray source occlusion, and detector volume averaging. Small volume and tissue-equivalent detectors are recommended to overcome the challenges. With the lack of a perfect radiation detector, studies on available detectors are ongoing with reasonable disagreement and uncertainties. The joint IAEA and AAPM international code of practice (CoP) for small field dosimetry, TRS 483 (Alfonso et al., 2017) provides guidelines and recommendations for the dosimetry of small static fields in external beam radiotherapy. The CoP provides a methodology for field output factor (FOF) measurements and use of field output correction factors for a series of small field detectors and strongly recommends additional measurements, data collection and verification for CyberKnife (CK) robotic stereotactic radiotherapy/radiosurgery system using the listed detectors and more new detectors so that the FOFs can be implemented clinically. The present investigation is focused on using 3D gel along with some other commercially available detectors for the measurement and verification of field output factors (FOFs) for the small fields available in the CK system. The FOF verification was performed through a comparison with published data and Monte Carlo simulation. The results of this study have proved the suitability of an in-house developed 3D polymer gel dosimeter, several commercially available detectors, and Gafchromic films as a part of small field dosimetric measurements for the CK system.
Collapse
|
3
|
Kaveckyte V, Jørgensen EB, Kertzscher G, Johansen JG, Tedgren ÅC. Monte Carlo characterization of high atomic number inorganic scintillators for in vivo dosimetry in 192 Ir brachytherapy. Med Phys 2022; 49:4715-4730. [PMID: 35443079 DOI: 10.1002/mp.15674] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 03/01/2022] [Accepted: 04/06/2022] [Indexed: 11/05/2022] Open
Abstract
BACKGROUND There is increased interest in vivo dosimetry for 192 Ir brachytherapy (BT) treatments using high atomic number (Z) inorganic scintillators. Their high light output enables construction of small detectors with negligible stem effect and simple readout electronics. Experimental determination of absorbed-dose energy dependence of detectors relative to water is prevalent, but it can be prone to high detector positioning uncertainties and does not allow for decoupling of absorbed-dose energy dependence from other factors affecting detector response. PURPOSE To investigate which measurement conditions and detector properties could affect their absorbed-dose energy dependence in BT in vivo dosimetry. METHODS We used a general-purpose MC code penelope for the characterization of high-Z inorganic scintillators with the focus on ZnSe (Z¯=32). Two other promising media CsI (Z¯=54) and Al2 O3 (Z¯=11) were included for comparison in selected scenarios. We determined absorbed-dose energy dependence of crystals relative to water under different scatter conditions (calibration phantom 12 × 12 × 30 cm3 , characterization phantoms 20 × 20 × 20 cm3 , 30 × 30 × 30 cm3 , 40 × 40 × 40 cm3 , and patient-like elliptic phantom 40 × 30 × 25 cm3 ). To mimic irradiation conditions during prostate treatments, we evaluated whether the presence of pelvic bones and calcifications affect ZnSe response. ZnSe detector design influence was also investigated. RESULTS In contrast to low-Z organic and medium-Z inorganic scintillators, ZnSe and CsI media have substantially greater absorbed-dose energy dependence relative to water. The response was phantom-size dependent and changed by 11 % between limited- and full-scatter conditions for ZnSe, but not for Al2 O3 . For a given phantom size, a part of the absorbed-dose energy dependence of ZnSe is caused not due to in-phantom scatter but due to source anisotropy. Thus, the absorbed-dose energy dependence of high-Z scintillators is a function of not only the radial distance but also the polar angle. Pelvic bones did not affect ZnSe response, whereas large and intermediate size calcifications reduced it by 9 % and 5 %, respectively, when placed midway between the source and the detector. CONCLUSIONS Unlike currently prevalent low- and medium-Z scintillators, high-Z crystals are sensitive to characterization and in vivo measurement conditions. However, good agreement between MC data for ZnSe in the present study and experimental data for ZnSe:O by Jørgensen et al (2021) suggest that detector signal is proportional to the average absorbed dose to the detector cavity. This enables an easy correction for non-TG43-like scenarios (e.g., patient sizes and calcifications) through MC simulations. Information that should be provided to the clinic by the detector vendors. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Vaiva Kaveckyte
- Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, SE-581 85, Sweden
| | - Erik B Jørgensen
- Department of Clinical Medicine, Aarhus University, Aarhus, DK-8000, Denmark.,Department of Oncology, Aarhus University Hospital, Aarhus, DK-8000, Denmark
| | - Gustavo Kertzscher
- Department of Oncology, Aarhus University Hospital, Aarhus, DK-8000, Denmark
| | - Jacob G Johansen
- Department of Clinical Medicine, Aarhus University, Aarhus, DK-8000, Denmark.,Department of Oncology, Aarhus University Hospital, Aarhus, DK-8000, Denmark
| | - Åsa Carlsson Tedgren
- Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, SE-581 85, Sweden.,Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, SE-171 76, Sweden.,Department of Oncology-Pathology, Karolinska Institute, Stockholm, SE-171 76, Sweden
| |
Collapse
|
4
|
Bouchard H. Reference dosimetry of modulated and dynamic photon beams. Phys Med Biol 2021; 65:24TR05. [PMID: 33438582 DOI: 10.1088/1361-6560/abc3fb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In the late 1980s, a new technique was proposed that would revolutionize radiotherapy. Now referred to as intensity-modulated radiotherapy, it is at the core of state-of-the-art photon beam delivery techniques, such as helical tomotherapy and volumetric modulated arc therapy. Despite over two decades of clinical application, there are still no established guidelines on the calibration of dynamic modulated photon beams. In 2008, the IAEA-AAPM work group on nonstandard photon beam dosimetry published a formalism to support the development of a new generation of protocols applicable to nonstandard beam reference dosimetry (Alfonso et al 2008 Med. Phys. 35 5179-86). The recent IAEA Code of Practice TRS-483 was published as a result of this initiative and addresses exclusively small static beams. But the plan-class specific reference calibration route proposed by Alfonso et al (2008 Med. Phys. 35 5179-86) is a change of paradigm that is yet to be implemented in radiotherapy clinics. The main goals of this paper are to provide a literature review on the dosimetry of nonstandard photon beams, including dynamic deliveries, and to discuss anticipated benefits and challenges in a future implementation of the IAEA-AAPM formalism on dynamic photon beams.
Collapse
Affiliation(s)
- Hugo Bouchard
- Département de physique, Université de Montréal, Complexe des sciences, 1375 Avenue Thérèse-Lavoie-Roux, Montréal, Québec H2V 0B3, Canada. Centre de recherche du Centre hospitalier de l'Université de Montréal, 900 Rue Saint-Denis, Montréal, Québec H2X 0A9, Canada. Département de radio-oncologie, Centre hospitalier de l'Université de Montréal (CHUM), 1051 Rue Sanguinet, Montréal, Québec H2X 3E4, Canada
| |
Collapse
|
5
|
Ghazal M, Westermark M, Kaveckyte V, Carlsson‐Tedgren Å, Benmakhlouf H. 6‐MV small field output factors: intra‐/intermachine comparison and implementation of TRS‐483 using various detectors and several linear accelerators. Med Phys 2019; 46:5350-5359. [DOI: 10.1002/mp.13830] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 09/05/2019] [Accepted: 09/05/2019] [Indexed: 11/10/2022] Open
Affiliation(s)
- Mohammed Ghazal
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
| | - Mathias Westermark
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
| | - Vaiva Kaveckyte
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
- Radiation Physics Department of Medical and Health Sciences Linköping University SE‐581 85Linköping Sweden
| | - Åsa Carlsson‐Tedgren
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
- Radiation Physics Department of Medical and Health Sciences Linköping University SE‐581 85Linköping Sweden
| | - Hamza Benmakhlouf
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
| |
Collapse
|
6
|
Palmans H, Andreo P, Huq MS, Seuntjens J, Christaki KE, Meghzifene A. Dosimetry of small static fields used in external photon beam radiotherapy: Summary of TRS‐483, the IAEA–AAPM international Code of Practice for reference and relative dose determination. Med Phys 2018; 45:e1123-e1145. [DOI: 10.1002/mp.13208] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/24/2018] [Accepted: 07/30/2018] [Indexed: 12/18/2022] Open
Affiliation(s)
- Hugo Palmans
- Medical Radiation Science National Physical Laboratory Teddington TW11 0LWUK
- Department of Medical Physics EBG MedAustron GmbH A‐2700Wiener Neustadt Austria
| | - Pedro Andreo
- Department of Medical Physics and Nuclear Medicine Karolinska University Hospital SE‐17176Stockholm Sweden
| | - M. Saiful Huq
- Department of Radiation Oncology University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center Pittsburgh PA15232USA
| | - Jan Seuntjens
- Medical Physics Unit McGill University Montréal QCH3A 0G4Canada
| | - Karen E. Christaki
- Dosimetry and Medical Radiation Physics Section International Atomic Energy Agency A‐1400Vienna Austria
| | - Ahmed Meghzifene
- Dosimetry and Medical Radiation Physics Section International Atomic Energy Agency A‐1400Vienna Austria
| |
Collapse
|
7
|
Parwaie W, Refahi S, Ardekani MA, Farhood B. Different Dosimeters/Detectors Used in Small-Field Dosimetry: Pros and Cons. JOURNAL OF MEDICAL SIGNALS & SENSORS 2018; 8:195-203. [PMID: 30181968 PMCID: PMC6116321 DOI: 10.4103/jmss.jmss_3_18] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
With the advent of complex and precise radiation therapy techniques, the use of relatively small fields is needed. Using such field sizes can cause uncertainty in dosimetry; therefore, special attention is required both in dose calculations and measurements. There are several challenges in small-field dosimetry such as the steep gradient of the radiation field, volume averaging effect, lack of charged particle equilibrium, partial occlusion of radiation source, beam alignment, and unable to use a reference dosimeter. Due to these challenges, special dosimeters are needed for small-field dosimetry, and this review article discusses this topic.
Collapse
Affiliation(s)
- Wrya Parwaie
- Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Soheila Refahi
- Department of Medical Physics, Faculty of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran
| | - Mahdieh Afkhami Ardekani
- Department of Radiology, Faculty of Para-Medicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran
| | - Bagher Farhood
- Department of Radiology and Medical Physics, Faculty of Paramedical Sciences, Kashan University of Medical Sciences, Kashan, Iran
| |
Collapse
|
8
|
Gholami S, Longo F, Nedaie HA, Berti A, Mousavi M, Meigooni AS. Application of Geant4 Monte Carlo simulation in dose calculations for small radiosurgical fields. Med Dosim 2017; 43:214-223. [PMID: 28988675 DOI: 10.1016/j.meddos.2017.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 08/21/2017] [Accepted: 08/25/2017] [Indexed: 11/17/2022]
Abstract
The Geant4 toolkit was used to develop a Monte Carlo (MC)-based engine for accurate dose calculations in small radiation field sizes. The Geant4 toolkit (version 10.1.p02) was used to simulate 6-MV photon beam of a Varian2100C linear accelerator that is being used for stereotactic radiosurgery (SRS) treatment with small radiation fields. Geometric models of 3 in-house designed radiosurgical divergent cones, with the diameters of their projections at the isocenter being 10, 20, and 30 mm, were simulated. The accuracy of the MC simulation technique was examined by reproducing several different simulated dosimetric parameters of the primary beams with the experimental data. The dose distributions are first checked for single beams for each cone, then standard multiple field (SMF) techniques are applied. A sample set of DICOM files from computed tomography (CT) scan imaging of a patient's head was converted to the Geant4 geometry format to implement MC-based engine for a clinical test. To validate the accuracy of the MC-based calculations for SMF arrangements, the isodose lines from MC simulation in water phantom were compared with the measured isodose lines using EBT3 Gafchromic film in Solid Water phantoms. Agreements between measured and simulated depth dose values and beam profiles for SRS cones were generally within 2%/2 mm. For output factors, the largest discrepancy was observed for 10 mm SRS cone, which was 1.7%. For SMF techniques, in SRS cones, the MC simulation and EBT3 Gafchromic film dosimetry were in acceptable agreement (5%/5 mm). Excellent agreement between the results of the MC-based and measured dose values for both single and SMF techniques in SRS cones indicates the ability of the Geant4 toolkit to be applied as the platform for treatment planning of advanced radiotherapy techniques.
Collapse
Affiliation(s)
- Somayeh Gholami
- Radiotherapy Oncology Research Centre, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran; The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, Trieste 34151, Italy.
| | - Francesco Longo
- Department of Physics, University of Trieste and INFN Trieste, Italy
| | - Hassan Ali Nedaie
- Radiotherapy Oncology Research Centre, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran
| | - Alessio Berti
- Department of Physics, University of Trieste and INFN Trieste, Italy
| | - Mehdi Mousavi
- Faculty of Medicine, Jirof University of Medical Sciences, Jiroft, Iran
| | - Ali S Meigooni
- Comprehensive Cancer Centers of Nevada, Las Vegas, NV, United States
| |
Collapse
|
9
|
De Coste V, Francescon P, Marinelli M, Masi L, Paganini L, Pimpinella M, Prestopino G, Russo S, Stravato A, Verona C, Verona-Rinati G. Is the PTW 60019 microDiamond a suitable candidate for small field reference dosimetry? ACTA ACUST UNITED AC 2017; 62:7036-7055. [DOI: 10.1088/1361-6560/aa7e59] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
10
|
Tyler MK, Liu PZY, Lee C, McKenzie DR, Suchowerska N. Small field detector correction factors: effects of the flattening filter for Elekta and Varian linear accelerators. J Appl Clin Med Phys 2016; 17:223-235. [PMID: 27167280 PMCID: PMC5690940 DOI: 10.1120/jacmp.v17i3.6059] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 01/12/2016] [Accepted: 01/11/2016] [Indexed: 11/24/2022] Open
Abstract
Flattening filter‐free (FFF) beams are becoming the preferred beam type for stereotactic radiosurgery (SRS) and stereotactic ablative radiation therapy (SABR), as they enable an increase in dose rate and a decrease in treatment time. This work assesses the effects of the flattening filter on small field output factors for 6 MV beams generated by both Elekta and Varian linear accelerators, and determines differences between detector response in flattened (FF) and FFF beams. Relative output factors were measured with a range of detectors (diodes, ionization chambers, radiochromic film, and microDiamond) and referenced to the relative output factors measured with an air core fiber optic dosimeter (FOD), a scintillation dosimeter developed at Chris O'Brien Lifehouse, Sydney. Small field correction factors were generated for both FF and FFF beams. Diode measured detector response was compared with a recently published mathematical relation to predict diode response corrections in small fields. The effect of flattening filter removal on detector response was quantified using a ratio of relative detector responses in FFF and FF fields for the same field size. The removal of the flattening filter was found to have a small but measurable effect on ionization chamber response with maximum deviations of less than ±0.9% across all field sizes measured. Solid‐state detectors showed an increased dependence on the flattening filter of up to ±1.6%. Measured diode response was within ±1.1% of the published mathematical relation for all fields up to 30 mm, independent of linac type and presence or absence of a flattening filter. For 6 MV beams, detector correction factors between FFF and FF beams are interchangeable for a linac between FF and FFF modes, providing that an additional uncertainty of up to ±1.6% is accepted. PACS number(s): 87.55.km, 87.56.bd, 87.56.Da
Collapse
|
11
|
Godson HF, Ravikumar M, Ganesh K, Sathiyan S, Ponmalar YR. Small field output factors: Comparison of measurements with various detectors and effects of detector orientation with primary jaw setting. RADIAT MEAS 2016. [DOI: 10.1016/j.radmeas.2015.12.038] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
12
|
Nguyen D, O'Connor D, Yu VY, Ruan D, Cao M, Low DA, Sheng K. Dose domain regularization of MLC leaf patterns for highly complex IMRT plans. Med Phys 2015; 42:1858-70. [PMID: 25832076 DOI: 10.1118/1.4915286] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The advent of automated beam orientation and fluence optimization enables more complex intensity modulated radiation therapy (IMRT) planning using an increasing number of fields to exploit the expanded solution space. This has created a challenge in converting complex fluences to robust multileaf collimator (MLC) segments for delivery. A novel method to regularize the fluence map and simplify MLC segments is introduced to maximize delivery efficiency, accuracy, and plan quality. METHODS In this work, we implemented a novel approach to regularize optimized fluences in the dose domain. The treatment planning problem was formulated in an optimization framework to minimize the segmentation-induced dose distribution degradation subject to a total variation regularization to encourage piecewise smoothness in fluence maps. The optimization problem was solved using a first-order primal-dual algorithm known as the Chambolle-Pock algorithm. Plans for 2 GBM, 2 head and neck, and 2 lung patients were created using 20 automatically selected and optimized noncoplanar beams. The fluence was first regularized using Chambolle-Pock and then stratified into equal steps, and the MLC segments were calculated using a previously described level reducing method. Isolated apertures with sizes smaller than preset thresholds of 1-3 bixels, which are square units of an IMRT fluence map from MLC discretization, were removed from the MLC segments. Performance of the dose domain regularized (DDR) fluences was compared to direct stratification and direct MLC segmentation (DMS) of the fluences using level reduction without dose domain fluence regularization. RESULTS For all six cases, the DDR method increased the average planning target volume dose homogeneity (D95/D5) from 0.814 to 0.878 while maintaining equivalent dose to organs at risk (OARs). Regularized fluences were more robust to MLC sequencing, particularly to the stratification and small aperture removal. The maximum and mean aperture sizes using the DDR were consistently larger than those from DMS for all tested number of segments. CONCLUSIONS The fluence map to MLC segmentation conversion problem was formulated as a secondary optimization problem in the dose domain to minimize the smoothness-regularized dose discrepancy. The large scale optimization problem was solved using a primal-dual algorithm that transformed complicated fluences into maps that were more robust to the MLC segmentation and sequencing, affording fewer and larger segments with minimal degradation to dose distribution.
Collapse
Affiliation(s)
- Dan Nguyen
- Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095
| | - Daniel O'Connor
- Department of Mathematics, University of California Los Angeles, Los Angeles, California 90095
| | - Victoria Y Yu
- Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095
| | - Dan Ruan
- Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095
| | - Minsong Cao
- Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095
| | - Daniel A Low
- Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095
| | - Ke Sheng
- Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095
| |
Collapse
|
13
|
Teke T, Duzenli C, Bergman A, Viel F, Atwal P, Gete E. Monte Carlo validation of the TrueBeam 10XFFF phase-space files for applications in lung SABR. Med Phys 2015; 42:6863-74. [PMID: 26632043 DOI: 10.1118/1.4935144] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
PURPOSE To establish the clinical acceptability of universal Monte Carlo phase-space data for the 10XFFF (flattening filter free) photon beam on the Varian TrueBeam Linac, including previously unreported data for small fields, output factors, and inhomogeneous media. The study was particularly aimed at confirming the suitability for use in simulations of lung stereotactic ablative radiotherapy treatment plans. METHODS Monte Carlo calculated percent depth doses (PDDs), transverse profiles, and output factors for the TrueBeam 10 MV FFF beam using generic phase-space data that have been released by the Varian MC research team were compared with in-house measurements and published data from multiple institutions (ten Linacs from eight different institutions). BEAMnrc was used to create field size specific phase-spaces located underneath the jaws. Doses were calculated with DOSXYZnrc in a water phantom for fields ranging from 1 × 1 to 40 × 40 cm(2). Particular attention was paid to small fields (down to 1 × 1 cm(2)) and dose per pulse effects on dosimeter response for high dose rate 10XFFF beams. Ion chamber measurements were corrected for changes in ion collection efficiency (P(ion)) with increasing dose per pulse. MC and ECLIPSE ANISOTROPIC ANALYTICAL ALGORITHM (AAA) calculated PDDs were compared to Gafchromic film measurement in inhomogeneous media (water, bone, lung). RESULTS Measured data from all machines agreed with Monte Carlo simulations within 1.0% and 1.5% for PDDs and in-field transverse profiles, respectively, for field sizes >1 × 1 cm(2) in a homogeneous water phantom. Agreements in the 80%-20% penumbra widths were better than 2 mm for all the fields that were compared. For all the field sizes considered, the agreement between their measured and calculated output factors was within 1.1%. Monte Carlo results for dose to water at water/bone, bone/lung, and lung/water interfaces as well as within lung agree with film measurements to within 2.8% for 10 × 10 and 3 × 3 cm(2) field sizes. This represents a significant improvement over the performance of the ECLIPSE AAA. CONCLUSIONS The 10XFFF phase-space data offered by the Varian Monte Carlo research team have been validated for clinical use using measured, interinstitutional beam data in water and with film dosimetry in inhomogeneous media.
Collapse
Affiliation(s)
- Tony Teke
- Medical Physics, BC Cancer Agency-Centre for the Southern Interior, Kelowna, British Columbia V1Y 5L3, Canada
| | - Cheryl Duzenli
- Medical Physics, BC Cancer Agency-Vancouver Centre, Vancouver, British Columbia V5Z 4E6, Canada
| | - Alanah Bergman
- Medical Physics, BC Cancer Agency-Vancouver Centre, Vancouver, British Columbia V5Z 4E6, Canada
| | - Francis Viel
- Medical Physics, BC Cancer Agency-Vancouver Centre, Vancouver, British Columbia V5Z 4E6, Canada
| | - Parmveer Atwal
- Medical Physics, BC Cancer Agency-Vancouver Centre, Vancouver, British Columbia V5Z 4E6, Canada
| | - Ermias Gete
- Medical Physics, BC Cancer Agency-Vancouver Centre, Vancouver, British Columbia V5Z 4E6, Canada
| |
Collapse
|
14
|
Benmakhlouf H, Johansson J, Paddick I, Andreo P. Monte Carlo calculated and experimentally determined output correction factors for small field detectors in Leksell Gamma Knife Perfexion beams. Phys Med Biol 2015; 60:3959-73. [DOI: 10.1088/0031-9155/60/10/3959] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
15
|
Benmakhlouf H, Sempau J, Andreo P. Output correction factors for nine small field detectors in 6 MV radiation therapy photon beams: A PENELOPE Monte Carlo study. Med Phys 2014; 41:041711. [DOI: 10.1118/1.4868695] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
16
|
Wang R, Pittet P, Ribouton J, Lu GN, Chaikh A, Ahnesjö A. Implementation and validation of a fluence pencil kernels model for GaN-based dosimetry in photon beam radiotherapy. Phys Med Biol 2013; 58:6701-12. [PMID: 24018737 DOI: 10.1088/0031-9155/58/19/6701] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Gallium nitride (GaN), a direct-gap semiconductor that is radioluminescent, can be used as a transducer yielding a high signal from a small detecting volume and thus potentially suitable for use in small fields and for high dose gradients. A common drawback of semiconductor dosimeters with effective atomic numbers higher than soft tissues is that their responses depend on the presence of low energy photons for which the photoelectric cross section varies strongly with atomic number, which may affect the accuracy of dosimetric measurements. To tackle this 'over-response' issue, we propose a model for GaN-based dosimetry with readout correction. The local photon spectrum is calculated by convolving fluence pencil kernel spectra with the beam aperture fluence distribution. The response of a GaN detector is modelled by combining large cavity theory and small cavity theory for the low and high energy components of the local spectrum. Monte Carlo simulations are employed for determination of specific correction factors for different GaN transducer sizes and irradiation conditions. Some model parameters such as the cut-off energy and partitioning energy are discussed. The accuracy of the GaN dosimetric response model has been evaluated for tissue phantom ratio experiments along the central axis. These experiments have shown that calculated and measured GaN responses stay within ±3% at all depths beyond the build-up depth. The calculated GaN response factor is also in good agreement with measured data (±2.5%). The validated model with response compensation improves significantly the accuracy of dosimetric measurements: below 2.5% deviation as compared to 13% without compensation, for a 10 × 10 cm(2) field, at depth from 1.5 to 22 cm.
Collapse
Affiliation(s)
- Ruoxi Wang
- Institut des Nanotechnologies de Lyon INL, CNRS UMR5270, Université Lyon 1, Villeurbanne, France
| | | | | | | | | | | |
Collapse
|
17
|
Czarnecki D, Zink K. Monte Carlo calculated correction factors for diodes and ion chambers in small photon fields. Phys Med Biol 2013; 58:2431-44. [DOI: 10.1088/0031-9155/58/8/2431] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
18
|
Scarboro SB, Kry SF. Characterisation of energy response of Al(2)O(3):C optically stimulated luminescent dosemeters (OSLDs) using cavity theory. RADIATION PROTECTION DOSIMETRY 2013; 153:23-31. [PMID: 22653437 PMCID: PMC3528097 DOI: 10.1093/rpd/ncs086] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 01/23/2012] [Accepted: 05/02/2012] [Indexed: 05/24/2023]
Abstract
Aluminium oxide (Al(2)O(3):C) is a common material used in optically stimulated luminescent dosemeters (OSLDs). OSLDs have a known energy dependence, which can impact on the accuracy of dose measurements, especially for lower photon energies, where the dosemeter can overrespond by a factor of 3-4. The purpose of this work was to characterise the response of Al(2)O(3):C using cavity theory and to evaluate the applicability of this approach for polyenergetic photon beams. The cavity theory energy response showed good agreement (within 2 %) with the corresponding measured values. A comparison with measured values reported in the literature for low-energy polyenergetic spectra showed more varied agreement (within 6 % on average). The discrepancy between these results is attributed to differences in the raw photon energy spectra used to calculate the energy response. Analysis of the impact of the photon energy spectra versus the mean photon energy showed improved accuracy if the energy response was determined using the entire photon spectrum rather than the mean photon energy. If not accounted for, the overresponse due to photon energy could introduce substantial inaccuracy in dose measurement using OSLDs, and the results of this study indicate that cavity theory may be used to determine the response with reasonable accuracy.
Collapse
Affiliation(s)
- S. B. Scarboro
- Department of Radiation Physics, Unit 607, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
- Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, 6767 Bertner Ave., Houston, TX 77030, USA
| | - S. F. Kry
- Department of Radiation Physics, Unit 607, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
- Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, 6767 Bertner Ave., Houston, TX 77030, USA
| |
Collapse
|
19
|
Brualla-González L, Gómez F, Vicedo A, González-Castaño DM, Gago-Arias A, Pazos A, Zapata M, Roselló JV, Pardo-Montero J. A two-dimensional liquid-filled ionization chamber array prototype for small-field verification: characterization and first clinical tests. Phys Med Biol 2012; 57:5221-34. [DOI: 10.1088/0031-9155/57/16/5221] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
20
|
Cranmer-Sargison G, Weston S, Evans JA, Sidhu NP, Thwaites DI. Monte Carlo modelling of diode detectors for small field MV photon dosimetry: detector model simplification and the sensitivity of correction factors to source parameterization. Phys Med Biol 2012; 57:5141-53. [DOI: 10.1088/0031-9155/57/16/5141] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
|
21
|
Ralston A, Liu P, Warrener K, McKenzie D, Suchowerska N. Small field diode correction factors derived using an air core fibre optic scintillation dosimeter and EBT2 film. Phys Med Biol 2012; 57:2587-602. [DOI: 10.1088/0031-9155/57/9/2587] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
22
|
Gago-Arias A, Brualla-González L, González-Castaño DM, Gómez F, García MS, Vega VL, Sueiro JM, Pardo-Montero J. Evaluation of chamber response function influence on IMRT verification using 2D commercial detector arrays. Phys Med Biol 2012; 57:2005-20. [DOI: 10.1088/0031-9155/57/7/2005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
23
|
Cranmer-Sargison G, Weston S, Evans JA, Sidhu NP, Thwaites DI. Implementing a newly proposed Monte Carlo based small field dosimetry formalism for a comprehensive set of diode detectors. Med Phys 2011; 38:6592-602. [DOI: 10.1118/1.3658572] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
24
|
Francescon P, Cora S, Satariano N. Calculation of kQclin,Qmsrfclin,fmsr for several small detectors and for two linear accelerators using Monte Carlo simulations. Med Phys 2011; 38:6513-27. [DOI: 10.1118/1.3660770] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|