51
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Jafari SM, Alalawi AI, Hussein M, Alsaleh W, Najem MA, Hugtenburg RP, Bradley DA, Spyrou NM, Clark CH, Nisbet A. Glass beads and Ge-doped optical fibres as thermoluminescence dosimeters for small field photon dosimetry. Phys Med Biol 2014; 59:6875-89. [DOI: 10.1088/0031-9155/59/22/6875] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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52
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Gersh JA, Best RCM, Watts RJ. The clinical impact of detector choice for beam scanning. J Appl Clin Med Phys 2014; 15:4801. [PMID: 25207408 PMCID: PMC5875504 DOI: 10.1120/jacmp.v15i4.4801] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 02/22/2014] [Accepted: 03/06/2014] [Indexed: 11/23/2022] Open
Abstract
Recently, the developers of Eclipse have recommended the use of ionization chambers for all profile scanning, including for the modeling of VMAT and stereotactic applications. The purpose of this study is to show the clinical impact caused by the choice of detector with respect to its ability to accurately measure dose in the penumbra and tail regions of a scanned profile. Using scan data acquired with several detectors, including an IBA CC13, a PTW 60012, and a Sun Nuclear EDGE Detector, three complete beam models are created, one for each respective detector. Next, using each beam model, dose volumes are retrospectively recalculated from actual anonymous patient plans. These plans include three full‐arc VMAT prostate plans, three left chest wall plans delivered using irregular compensators, two half‐arc VMAT lung plans, three MLC‐collimated static‐field pairs, and two SBRT liver plans. Finally, plans are reweighted to deliver the same number of monitor units, and mean dose‐to‐target volumes and organs at risk are calculated and compared. Penumbra width did not play a role. Dose in the tail region of the profile made the largest difference. By overresponding in the tail region of the profile, the 60012 diode detector scan data affected the beam model in such a way that target doses were reduced by as much as 0.4% (in comparison to CC13 and EDGE data). This overresponse also resulted in an overestimation of dose to peripheral critical structure, whose dose consisted mainly of scatter. This study shows that, for modeling the 6 MV beam of Acuros XB in Eclipse Version 11, the choice to use a CC13 scanning ion chamber or an EDGE Detector was an unimportant choice, providing nearly identical models in the treatment planning system. PACS number: 87.55.kh
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Azangwe G, Grochowska P, Georg D, Izewska J, Hopfgartner J, Lechner W, Andersen CE, Beierholm AR, Helt-Hansen J, Mizuno H, Fukumura A, Yajima K, Gouldstone C, Sharpe P, Meghzifene A, Palmans H. Detector to detector corrections: A comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams. Med Phys 2014; 41:072103. [DOI: 10.1118/1.4883795] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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54
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Moignier C, Huet C, Makovicka L. Determination of the kQclin,Qmsrfclin,fmsr correction factors for detectors used with an 800 MU/min CyberKnife®
system equipped with fixed collimators and a study of detector response to small photon beams using a Monte Carlo method. Med Phys 2014; 41:071702. [DOI: 10.1118/1.4881098] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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55
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Wagner A, Crop F, Lacornerie T, Reynaert N. Characterization of recombination effects in a liquid ionization chamber used for the dosimetry of a radiosurgical accelerator. J Vis Exp 2014. [PMID: 24835586 PMCID: PMC4174048 DOI: 10.3791/51296] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Most modern radiation therapy devices allow the use of very small fields, either through beamlets in Intensity-Modulated Radiation Therapy (IMRT) or via stereotactic radiotherapy where positioning accuracy allows delivering very high doses per fraction in a small volume of the patient. Dosimetric measurements on medical accelerators are conventionally realized using air-filled ionization chambers. However, in small beams these are subject to nonnegligible perturbation effects. This study focuses on liquid ionization chambers, which offer advantages in terms of spatial resolution and low fluence perturbation. Ion recombination effects are investigated for the microLion detector (PTW) used with the Cyberknife system (Accuray). The method consists of performing a series of water tank measurements at different source-surface distances, and applying corrections to the liquid detector readings based on simultaneous gaseous detector measurements. This approach facilitates isolating the recombination effects arising from the high density of the liquid sensitive medium and obtaining correction factors to apply to the detector readings. The main difficulty resides in achieving a sufficient level of accuracy in the setup to be able to detect small changes in the chamber response.
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Barbés B, Azcona JD, Burguete J, Martí-Climent JM. Application of spherical diodes for megavoltage photon beams dosimetry. Med Phys 2014; 41:012102. [PMID: 24387520 DOI: 10.1118/1.4837178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE External beam radiation therapy (EBRT) usually uses heterogeneous dose distributions in a given volume. Designing detectors for quality control of these treatments is still a developing subject. The size of the detectors should be small to enhance spatial resolution and ensure low perturbation of the beam. A high uniformity in angular response is also a very important feature in a detector, because it has to measure radiation coming from all the directions of the space. It is also convenient that detectors are inexpensive and robust, especially to perform in vivo measurements. The purpose of this work is to introduce a new detector for measuring megavoltage photon beams and to assess its performance to measure relative dose in EBRT. METHODS The detector studied in this work was designed as a spherical photodiode (1.8 mm in diameter). The change in response of the spherical diodes is measured regarding the angle of incidence, cumulated irradiation, and instantaneous dose rate (or dose per pulse). Additionally, total scatter factors for large and small fields (between 1 × 1 cm(2) and 20 × 20 cm(2)) are evaluated and compared with the results obtained from some commercially available ionization chambers and planar diodes. Additionally, the over-response to low energy scattered photons in large fields is investigated using a shielding layer. RESULTS The spherical diode studied in this work produces a high signal (150 nC/Gy for photons of nominal energy of 15 MV and 160 for 6 MV, after 12 kGy) and its angular dependence is lower than that of planar diodes: less than 5% between maximum and minimum in all directions, and 2% around one of the axis. It also has a moderated variation with accumulated dose (about 1.5%/kGy for 15 MV photons and 0.7%/kGy for 6 MV, after 12 kGy) and a low variation with dose per pulse (± 0.4%), and its behavior is similar to commercial diodes in total scatter factor measurements. CONCLUSIONS The measurements of relative dose using the spherical diode described in this work show its feasibility for the dosimetry of megavoltage photon beams. A particularly important feature is its good angular response in the MV range. They would be good candidates for in vivo dosimetry, and quality assurance of VMAT and tomotherapy, and other modalities with beams irradiating from multiple orientations, such as Cyberknife and ViewRay, with minor modifications.
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Affiliation(s)
- Benigno Barbés
- Servicio de Oncología Radioterápica, Clínica Universidad de Navarra, Avda. Pío XII, 36, E-31008 Pamplona, Navarra, Spain
| | - Juan D Azcona
- Department of Radiation Oncology, Stanford University, Stanford, California 94305 and Servicio de Oncología Radioterápica, Clínica Universidad de Navarra, Avda. Pío XII 36, E-31008 Pamplona, Navarra, Spain
| | - Javier Burguete
- Departamento de Física y Matemática Aplicada, Facultad de Ciencias, Universidad de Navarra, Irunlarrea 1, E-31008 Pamplona, Navarra, Spain
| | - Josep M Martí-Climent
- Servicio de Medicina Nuclear, Clínica Universidad de Navarra, Avda. Pío XII 36, E-31008 Pamplona, Navarra, Spain
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Almendral P, Mancha PJ, Roberto D. Feasibility of a simple method of hybrid collimation for megavoltage grid therapy. Med Phys 2013; 40:051712. [PMID: 23635260 DOI: 10.1118/1.4801902] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Megavoltage grid therapy is currently delivered with step-and-shoot multisegment techniques or using a high attenuation block with divergent holes. However, the commercial availability of grid blocks is limited, their construction is difficult, and step-and-shoot techniques require longer treatment times and are not practical with some multileaf collimators. This work studies the feasibility of a hybrid collimation system for grid therapy that does not require multiple segments and can be easily implemented with widely available technical means. METHODS The authors have developed a system to generate a grid of beamlets by the simultaneous use of two perpendicular sets of equally spaced leaves that project stripe patterns in orthogonal directions. One of them is generated with the multileaf collimator integrated in the accelerator and the other with an in-house made collimator constructed with a low melting point alloy commonly available at radiation oncology departments. The characteristics of the grid fields for 6 and 18 MV have been studied with a shielded diode, an unshielded diode, and radiochromic film. RESULTS The grid obtained with the hybrid collimation is similar to some of the grids used clinically with respect to the beamlet size (about 1 cm) and the percentage of open beam (1/4 of the total field). The grid fields are less penetrating than the open fields of the same energy. Depending on the depth and the direction of the profiles (diagonal or along the principal axes), the measured valley-to-peak dose ratios range from 5% to 16% for 6 MV and from 9% to 20% for 18 MV. All the detectors yield similar results in the measurement of profiles and percent depth dose, but the shielded diode seems to overestimate the output factors. CONCLUSIONS The combination of two stripe pattern collimators in orthogonal directions is a feasible method to obtain two-dimensional arrays of beamlets and has potential usefulness as an efficient way to deliver grid therapy. The implementation of this method is technically simpler than the construction of a conventional grid block.
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Affiliation(s)
- Pedro Almendral
- Servicio de Protección Radiológica y Radiofísica Hospitalaria, Hospital Infanta Cristina, 06080 Badajoz, Spain.
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Lechner W, Palmans H, Sölkner L, Grochowska P, Georg D. Detector comparison for small field output factor measurements in flattening filter free photon beams. Radiother Oncol 2013; 109:356-60. [DOI: 10.1016/j.radonc.2013.10.022] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 10/11/2013] [Accepted: 10/19/2013] [Indexed: 11/28/2022]
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Bagalà P, Di Venanzio C, Falco MD, Guerra AS, Marinelli M, Milani E, Pimpinella M, Pompili F, Prestopino G, Santoni R, Tonnetti A, Verona C, Verona-Rinati G. Radiotherapy electron beams collimated by small tubular applicators: characterization by silicon and diamond diodes. Phys Med Biol 2013; 58:8121-33. [DOI: 10.1088/0031-9155/58/22/8121] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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60
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Benítez E, Casado F, García-Pareja S, Martín-Viera J, Moreno C, Parra V. Evaluation of a liquid ionization chamber for relative dosimetry in small and large fields of radiotherapy photon beams. RADIAT MEAS 2013. [DOI: 10.1016/j.radmeas.2013.08.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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61
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Marsolat F, Tromson D, Tranchant N, Pomorski M, Le Roy M, Donois M, Moignau F, Ostrowsky A, De Carlan L, Bassinet C, Huet C, Derreumaux S, Chea M, Cristina K, Boisserie G, Bergonzo P. A new single crystal diamond dosimeter for small beam: comparison with different commercial active detectors. Phys Med Biol 2013; 58:7647-60. [DOI: 10.1088/0031-9155/58/21/7647] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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62
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Cranmer-Sargison G, Liu PZY, Weston S, Suchowerska N, Thwaites DI. Small field dosimetric characterization of a new 160-leaf MLC. Phys Med Biol 2013; 58:7343-54. [DOI: 10.1088/0031-9155/58/20/7343] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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63
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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.
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Affiliation(s)
- Ruoxi Wang
- Institut des Nanotechnologies de Lyon INL, CNRS UMR5270, Université Lyon 1, Villeurbanne, France
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64
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The dose response functions of ionization chambers in photon dosimetry – Gaussian or non-Gaussian? Z Med Phys 2013; 23:129-43. [DOI: 10.1016/j.zemedi.2012.12.010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 12/05/2012] [Accepted: 12/21/2012] [Indexed: 11/22/2022]
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65
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Wagner A, Crop F, Lacornerie T, Vandevelde F, Reynaert N. Use of a liquid ionization chamber for stereotactic radiotherapy dosimetry. Phys Med Biol 2013; 58:2445-59. [DOI: 10.1088/0031-9155/58/8/2445] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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66
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Di Venanzio C, Marinelli M, Milani E, Prestopino G, Verona C, Verona-Rinati G, Falco MD, Bagalà P, Santoni R, Pimpinella M. Characterization of a synthetic single crystal diamond Schottky diode for radiotherapy electron beam dosimetry. Med Phys 2013; 40:021712. [DOI: 10.1118/1.4774360] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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67
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Morin J, Béliveau-Nadeau D, Chung E, Seuntjens J, Thériault D, Archambault L, Beddar S, Beaulieu L. A comparative study of small field total scatter factors and dose profiles using plastic scintillation detectors and other stereotactic dosimeters: The case of the CyberKnife. Med Phys 2013; 40:011719. [DOI: 10.1118/1.4772190] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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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
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69
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Lacroix F, Guillot M, McEwen M, Gingras L, Beaulieu L. Extraction of depth-dependent perturbation factors for silicon diodes using a plastic scintillation detector. Med Phys 2011; 38:5441-7. [DOI: 10.1118/1.3637496] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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70
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Experimental small field 6MV output ratio analysis for various diode detector and accelerator combinations. Radiother Oncol 2011; 100:429-35. [DOI: 10.1016/j.radonc.2011.09.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 09/02/2011] [Accepted: 09/03/2011] [Indexed: 11/21/2022]
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71
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Commissioning of Photon Beams of a Flattening Filter-Free Linear Accelerator and the Accuracy of Beam Modeling Using an Anisotropic Analytical Algorithm. Int J Radiat Oncol Biol Phys 2011; 80:1228-37. [DOI: 10.1016/j.ijrobp.2010.09.050] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 09/08/2010] [Accepted: 09/28/2010] [Indexed: 11/21/2022]
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72
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González W, Lallena AM, Alfonso R. Monte Carlo simulation of the dynamic micro-multileaf collimator of a LINAC Elekta Precise using PENELOPE. Phys Med Biol 2011; 56:3417-31. [DOI: 10.1088/0031-9155/56/11/015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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73
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González-Castaño D, Gómez F, Brualla L, Roselló J, Planes D, Sánchez M, Pombar M. A liquid-filled ionization chamber for high precision relative dosimetry. Phys Med 2011; 27:89-96. [DOI: 10.1016/j.ejmp.2010.04.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2009] [Revised: 03/31/2010] [Accepted: 04/28/2010] [Indexed: 10/19/2022] Open
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74
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Low DA, Moran JM, Dempsey JF, Dong L, Oldham M. Dosimetry tools and techniques for IMRT. Med Phys 2011; 38:1313-38. [DOI: 10.1118/1.3514120] [Citation(s) in RCA: 298] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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75
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Eklund K, Ahnesjö A. Modeling silicon diode dose response factors for small photon fields. Phys Med Biol 2010; 55:7411-23. [DOI: 10.1088/0031-9155/55/24/002] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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76
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Lacroix F, Guillot M, McEwen M, Cojocaru C, Gingras L, Beddar AS, Beaulieu L. Extraction of depth-dependent perturbation factors for parallel-plate chambers in electron beams using a plastic scintillation detector. Med Phys 2010; 37:4331-42. [PMID: 20879593 DOI: 10.1118/1.3463383] [Citation(s) in RCA: 32] [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 This work presents the experimental extraction of the overall perturbation factor PQ in megavoltage electron beams for NACP-02 and Roos parallel-plate ionization chambers using a plastic scintillation detector (PSD). METHODS The authors used a single scanning PSD mounted on a high-precision scanning tank to measure depth-dose curves in 6, 12, and 18 MeV clinical electron beams. The authors also measured depth-dose curves using the NACP-02 and PTW Roos chambers. RESULTS The authors found that the perturbation factors for the NACP-02 and Roos chambers increased substantially with depth, especially for low-energy electron beams. The experimental results were in good agreement with the results of Monte Carlo simulations reported by other investigators. The authors also found that using an effective point of measurement (EPOM) placed inside the air cavity reduced the variation of perturbation factors with depth and that the optimal EPOM appears to be energy dependent. CONCLUSIONS A PSD can be used to experimentally extract perturbation factors for ionization chambers. The dosimetry protocol recommendations indicating that the point of measurement be placed on the inside face of the front window appear to be incorrect for parallel-plate chambers and result in errors in the R50 of approximately 0.4 mm at 6 MeV, 1.0 mm at 12 MeV, and 1.2 mm at 18 MeV.
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Affiliation(s)
- Frédéric Lacroix
- Département de Radio-Oncologie, Centre hospitalier de l'Université de Montréal, Québec, Canada.
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77
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Mapping radiation quality inside photon-irradiated absorbers by means of a twin-chamber method. Z Med Phys 2009; 19:252-63. [DOI: 10.1016/j.zemedi.2009.05.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 05/28/2009] [Accepted: 05/30/2009] [Indexed: 11/22/2022]
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78
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Eklund K, Ahnesjö A. Modeling silicon diode energy response factors for use in therapeutic photon beams. Phys Med Biol 2009; 54:6135-50. [DOI: 10.1088/0031-9155/54/20/007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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79
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Scherf C, Peter C, Moog J, Licher J, Kara E, Zink K, Rödel C, Ramm U. Silicon Diodes as an Alternative to Diamond Detectors for Depth Dose Curves and Profile Measurements of Photon and Electron Radiation. Strahlenther Onkol 2009; 185:530-6. [DOI: 10.1007/s00066-009-2004-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Accepted: 03/05/2009] [Indexed: 10/20/2022]
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80
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Djouguela A, Harder D, Kollhoff R, Foschepoth S, Kunth W, Rühmann A, Willborn K, Poppe B. Fourier deconvolution reveals the role of the Lorentz function as the convolution kernel of narrow photon beams. Phys Med Biol 2009; 54:2807-27. [DOI: 10.1088/0031-9155/54/9/015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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81
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Collomb-Patton V, Boher P, Leroux T, Fontbonne JM, Vela A, Batalla A. The DOSIMAP, a high spatial resolution tissue equivalent 2D dosimeter for LINAC QA and IMRT verification. Med Phys 2009; 36:317-28. [PMID: 19291971 DOI: 10.1118/1.3013703] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The continual need for more accurate and effective techniques in radiation therapy makes it necessary to devise new control means combining high spatial resolution as well as high dose accuracy. Intensity modulated radio therapy (IMRT) allows highly conformed fields with high spatial gradient and therefore requires a precise monitoring of all the multileaf positions. In response to this need, the authors have developed a new 2D tissue equivalent dosimeter with high spatial resolution. A plastic scintillator sheet is sandwiched between two polystyrene blocks and the emitted light is captured by a high resolution camera. A newly developed procedure described herein allows efficient discrimination of the scintillation from the parasitic Cerenkov radiation. This processing is applied on the cumulated image from a sequence of images taken during an irradiation field at a rate of 10 images/s. It provides a high resolution mapping of the cumulated dose in quasireal time. The dosimeter is tissue equivalent (ICRU-44) and works both for electrons and photons without complex parameter adjustment since phantom and detector materials are identical. Instrument calibration is simple and independent of the irradiation conditions (energy, fluence, quality, ...). In this article, the authors present the principle of the dosimeter and its calibration procedure. They compare the results obtained for photons and electron beams with ionization chamber measurements in polystyrene. Technical specifications such as accuracy and repeatability are precisely evaluated and discussed. Finally, they present different IMRT field measurements and compare DOSIMAP measurements to TPS simulations and dosimetric film profiles. The results confirm the excellent spatial resolution of the instrument and its capacity to inspect the leaf positions for each segment of a given field.
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82
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Francescon P, Cora S, Cavedon C, Scalchi P. Application of a Monte Carlo-based method for total scatter factors of small beams to new solid state micro-detectors. J Appl Clin Med Phys 2009; 10:147-152. [PMID: 19223843 PMCID: PMC5720495 DOI: 10.1120/jacmp.v10i1.2939] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Accepted: 10/17/2008] [Indexed: 11/23/2022] Open
Abstract
The scope of this work was to apply a method for estimation of total scatter factors of the smallest beams of the Cyberknife radiosurgery system to newly available solid‐state detectors: the PTW 60008 diode, the SunNuclear EdgeDetector™ diode, and the Thomson and Nielsen TN502RDM micromosfet. The method is based on a consistency check between Monte Carlo simulation of the detectors and experimental results, and was described in a recent publication. Corrected total scatter factors were in excellent agreement with the findings of the former study. The results showed that the diodes tend to overestimate the total scatter factor of small beams, probably due to excessive scatter from the material surrounding the active layer. The correction factor for diodes and for the micromosfet, however, was found to be independent of the electron beam width. This is a desirable characteristic because it allows standard correction factors to be used for treatment units of the same type, without the need of case‐by‐case Monte Carlo simulation. PACS numbers: 87.55.kh; 87.55.ne; 87.56.Fc.
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Affiliation(s)
| | - Stefania Cora
- Department of Medical Physics, ULSS6 "Vicenza", Vicenza, Italy
| | - Carlo Cavedon
- Department of Medical Physics, ULSS6 "Vicenza", Vicenza, Italy
| | - Paolo Scalchi
- Department of Medical Physics, ULSS6 "Vicenza", Vicenza, Italy
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83
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Dosimetric characteristics of an unshielded p-type Si diode: linearity, photon energy dependence and spatial resolution. Z Med Phys 2008; 18:301-6. [DOI: 10.1016/j.zemedi.2008.06.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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84
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Scott AJD, Nahum AE, Fenwick JD. Using a Monte Carlo model to predict dosimetric properties of small radiotherapy photon fields. Med Phys 2008; 35:4671-84. [DOI: 10.1118/1.2975223] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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85
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Collomb-Patton V, Boher P, Leroux T, Fontbonne JM, Batalla A, Vela A. DOSIMAP: a high-resolution 2-D tissue equivalent dosemeter for linac QA and IMRT verification. RADIATION PROTECTION DOSIMETRY 2008; 131:100-109. [PMID: 18757897 DOI: 10.1093/rpd/ncn228] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
New generation of radiation therapy accelerators requires highly accurate dose measurements with high spatial resolution patterns. IMRT is especially demanding since the positioning accuracy of all the multi-leafs should be verified for each applied field and at any incidence. A new 2-D tissue equivalent dosemeter is presented with high spatial resolution that can fulfil these tasks. A plastic scintillator sheet is sandwiched between two polystyrene cubes, and the emitted light is observed by a high-resolution camera. A patented procedure allows efficient discrimination of the scintillation proportional to the dose from the parasitic Cerenkov radiation. This extraction made on the cumulated images taken during an irradiation field at a rate of 10 images s(-1) provides high-resolution mapping of the dose rate and cumulated dose in quasi real time. The dosemeter is tissue equivalent (ICRU-44) and works both for electrons and photons without complex parameter adjustment, since phantom and detector materials are identical. The calibration is simple and independent of the irradiation conditions (energy, fluence, quality and so on). The principle of the dosemeter and its calibration procedure are discussed in this paper. The results and, in particular, the dose depth profiles are compared with standard ionisation chamber measurements in polystyrene for both photons and electrons. Finally, the detector specifications are summarised and one example of complex IMRT field is discussed.
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86
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Das IJ, Cheng CW, Watts RJ, Ahnesjö A, Gibbons J, Li XA, Lowenstein J, Mitra RK, Simon WE, Zhu TC. Accelerator beam data commissioning equipment and procedures: Report of the TG-106 of the Therapy Physics Committee of the AAPM. Med Phys 2008; 35:4186-215. [PMID: 18841871 DOI: 10.1118/1.2969070] [Citation(s) in RCA: 302] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Indra J Das
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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87
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Wilcox EE, Daskalov GM. Accuracy of dose measurements and calculations within and beyond heterogeneous tissues for 6MV photon fields smaller than 4cm produced by Cyberknife. Med Phys 2008; 35:2259-66. [DOI: 10.1118/1.2912179] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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88
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Francescon P, Cora S, Cavedon C. Total scatter factors of small beams: a multidetector and Monte Carlo study. Med Phys 2008; 35:504-13. [PMID: 18383671 DOI: 10.1118/1.2828195] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The scope of this study was to estimate total scatter factors (S(c,p)) of the three smallest collimators of the Cyberknife radiosurgery system (5-10 mm in diameter), combining experimental measurements and Monte Carlo simulation. Two microchambers, a diode, and a diamond detector were used to collect experimental data. The treatment head and the detectors were simulated by means of a Monte Carlo code in order to calculate correction factors for the detectors and to estimate total scatter factors by means of a consistency check between measurement and simulation. Results for the three collimators were: S(c,p) (5 mm) = 0.677 +/- 0.004, S(c,p) (7.5 mm) = 0.820 +/- 0.008, S(c,p) (10 mm) = 0.871 +/- 0.008, all relative to the 60 mm collimator at 80 cm source-to-detector distance. The method also allows the full width at half maximum of the electron beam to be estimated; estimations made with different collimators and different detectors were in excellent agreement and gave a value of 2.1 mm. Correction factors to be applied to the detectors for the measurement of S(c,p) were consistent with a prevalence of volume effect for the microchambers and the diamond and a prevalence of scattering from high-Z material for the diode detector. The proposed method is more sensitive to small variations of the electron beam diameter with respect to the conventional method used to commission Monte Carlo codes, i.e., by comparison with measured percentage depth doses (PDD) and beam profiles. This is especially important for small fields (less than 10 mm diameter), for which measurements of PDD and profiles are strongly affected by the type of detector used. Moreover, this method should allow S(c,p) of Cyberknife systems different from the unit under investigation to be estimated without the need for further Monte Carlo calculation, provided that one of the microchambers or the diode detector of the type used in this study are employed. The results for the diamond are applicable only to the specific detector that was investigated due to excessive variability in manufacturing.
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89
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Ma CM, Li JS, Deng J, Fan J. Implementation of Monte Carlo Dose calculation for CyberKnife treatment planning. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/102/1/012016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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90
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Best S, Ralston A, McKenzie D, Suchowerska N. Effect of scatter material on diode detector performance forin vivodosimetry. Phys Med Biol 2007; 53:89-97. [DOI: 10.1088/0031-9155/53/1/006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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91
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Sharma SC, Ott JT, Williams JB, Dickow D. Commissioning and acceptance testing of a CyberKnife linear accelerator. J Appl Clin Med Phys 2007; 8:119-125. [PMID: 17712305 PMCID: PMC5722603 DOI: 10.1120/jacmp.v8i3.2473] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 06/04/2007] [Accepted: 05/15/2007] [Indexed: 11/23/2022] Open
Abstract
Acceptance testing and commissioning of a CyberKnife robotic stereotactic radiosurgery system was performed in April 2006. The CyberKnife linear accelerator produces a photon beam of 6 MV nominal energy, without the use of a flattening filter. Clinically measured tissue-phantom ratios, off-center ratios, and output factors are presented and compared with similar data from other CyberKnife sites throughout the United States. In general, these values agreed to within 2%.
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Affiliation(s)
| | - Joseph T. Ott
- Parkview Comprehensive Cancer CenterFort WayneIndianaU.S.A.
| | | | - Danny Dickow
- Parkview Comprehensive Cancer CenterFort WayneIndianaU.S.A.
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92
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Schwedas M, Scheithauer M, Wiezorek T, Wendt TG. Strahlenphysikalische Einflussgrößen bei der Dosimetrie mit verschiedenen Detektortypen. Z Med Phys 2007; 17:172-9. [PMID: 17879814 DOI: 10.1016/j.zemedi.2007.03.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The present study investigated the radiophysical influences on the measurement of dosimetry basic data, attributable to field size, photon energy and detector type. A natural diamond detector, two ionisation chambers, different Si-diodes and a EBT-Gafchromic film were studied for this purpose. The characteristics of the detectors were investigated with regard to the measurement of output factors, lateral beam profiles and relative depth-dose curves for narrow and wide photon beams of 15 MV Significant differences in output factors were obtained with different detectors. For narrow fields, the natural diamond detector and the diodes PTW-60012 and SCX_WH-PFD measured output factors close to those of the EBT-Gafchromic film. The output facto rfor large fields was overestimated by the unshielded diode PTW 60012 and the PinPoint-chamber PTW-31006 because of their over-response to scattered photons. The relative depth dose distributions for wide beams at large depths agree well for the diamond, the ionisation chambers and the shielded Diode SCX_ WH-PFD and PTW-60008, while the measured dose was overestimated by an unshielded diode PTW-60012. Considering the influence due to the sensitive materials and the construction of the detectors the manufacturers of dosimeters have specified the application ranges for the various types of detectors.
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Affiliation(s)
- Michael Schwedas
- Universitätsklinikum Jena, Klinik für Strahlentherapie und Radioonkologie.
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93
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Alaei P, Higgins P, Gerbi B. SU-FF-T-197: Effect of the Added Buildup On P-Type Silicon Diodes' Response in Daily in Vivo Dosimetry Measurements. Med Phys 2007. [DOI: 10.1118/1.2760857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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94
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Abstract
Silicon semiconductor diodes measure almost the same depth-dose distributions in both photon and electron beams as those measured by ion chambers. A recent study in ion chamber dosimetry has suggested that the wall correction factor for a parallel-plate ion chamber in electron beams changes with depth by as much as 6%. To investigate diode detector response with respect to depth, a silicon diode model is constructed and the water/silicon dose ratio at various depths in electron beams is calculated using EGSnrc. The results indicate that, for this particular diode model, the diode response per unit water dose (or water/diode dose ratio) in both 6 and 18 MeV electron beams is flat within 2% versus depth, from near the phantom surface to the depth of R50 (with calculation uncertainty <0.3%). This suggests that there must be some other correction factors for ion chambers that counter-balance the large wall correction factor at depth in electron beams. In addition, the beam quality and field-size dependence of the diode model are also calculated. The results show that the water/diode dose ratio remains constant within 2% over the electron energy range from 6 to 18 MeV. The water/diode dose ratio does not depend on field size as long as the incident electron beam is broad and the electron energy is high. However, for a very small beam size (1 X 1 cm(2)) and low electron energy (6 MeV), the water/diode dose ratio may decrease by more than 2% compared to that of a broad beam.
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Affiliation(s)
- Lilie L W Wang
- Physics Department, Carleton University, Ottawa KIS 5B6, Canada
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95
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96
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Poppe B, Blechschmidt A, Djouguela A, Kollhoff R, Rubach A, Willborn KC, Harder D. Two-dimensional ionization chamber arrays for IMRT plan verification. Med Phys 2006; 33:1005-15. [PMID: 16696477 DOI: 10.1118/1.2179167] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In this paper we describe a concept for dosimetric treatment plan verification using two-dimensional ionization chamber arrays. Two different versions of the 2D-ARRAY (PTW-Freiburg, Germany) will be presented, a matrix of 16 x 16 chambers (chamber cross section 8 mm x 8 mm; the distance between chamber centers, 16 mm) and a matrix of 27 x 27 chambers (chamber cross section 5 mm x 5 mm; the distance between chamber centers is 10 mm). The two-dimensional response function of a single chamber is experimentally determined by scanning it with a slit beam. For dosimetric plan verification, the expected two-dimensional distribution of the array signals is calculated via convolution of the planned dose distribution, obtained from the treatment planning system, with the two-dimensional response function of a single chamber. By comparing the measured two-dimensional distribution of the array signals with the expected one, a distribution of deviations is obtained that can be subjected to verification criteria, such as the gamma index criterion. As an example, this verification method is discussed for one sequence of an IMRT plan. The error detection capability is demonstrated in a case study. Both versions of two-dimensional ionization chamber arrays, together with the developed treatment plan verification strategy, have been found to provide a suitable and easy-to-handle quality assurance instrument for IMRT.
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Affiliation(s)
- Bjoern Poppe
- Klinik fuer Strahlentherapie und Internistische Onkologie, Pius-Hospital, Oldenburg, Germany.
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97
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d'Errico F. Dosimetric issues in radiation protection of radiotherapy patients. RADIATION PROTECTION DOSIMETRY 2006; 118:205-12. [PMID: 16581918 DOI: 10.1093/rpd/ncl034] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
As life expectancy increases, thanks to improving general medical practices, cancer treatments for the ageing population become evermore necessary. Radiation therapy is increasingly a treatment of choice, promoted by continuing improvements in dose delivery technologies. Some techniques, collectively referred to as intensity-modulated radiation therapy, are encountering widespread acceptance and implementation, promoted by reports of superior tumour control and reduced toxicity. However, these new techniques pose new challenges in terms of radiation protection of patients, as they cause a more extensive low-dose exposure of normal tissues compared with conventional radiation therapy. The related dosimetric challenges and the methods available to tackle them are reviewed in this paper, which also emphasises the need for standard radiation protection dosimetry procedures so that information may be consistently gathered for a comparative evaluation of the different treatment modalities.
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Affiliation(s)
- Francesco d'Errico
- Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione, Università di Pisa, Italy.
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98
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Djouguela A, Harder D, Kollhoff R, Rühmann A, Willborn KC, Poppe B. The dose-area product, a new parameter for the dosimetry of narrow photon beams. Z Med Phys 2006; 16:217-27. [PMID: 16986461 DOI: 10.1078/0939-3889-00317] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In the dosimetry of narrow photon fields with side lengths of the order of 1 cm, the traditional parametrisation via the absolute dose on the beam axis and the relative lateral dose distribution has to deal with the difficulty to find sufficiently small detectors and to adjust them accurately on the narrow-beam axis. This can be avoided by reconsidering the parametrisation, using as normalization factor the surface integral of the dose in the plane perpendicular to the beam axis, abbreviated as the "dose-area product" (DAP). We investigated and confirmed the ability of a large-area parallel-plate ionisation chamber, with a sensitive volume shaped as a flat cylinder of 81.6 mm diameter and 2 mm thickness, to perform the integration over the full lateral dose profile of narrow photon beams with side lengths up to 5 cm. The lateral adjustment of this large-area detector relative to a narrow photon beam is not critical. The large-area ionisation chamber was calibrated in terms of the DAP by reference to a 0.3 cm3 ionisation chamber. A field-size dependent "modified output factor" was defined as the ratio of the DAP measured at 5 cm phantom depth for 100 cm SSD, and the monitor reading. A prominent phenomenon of narrow photon fields is the field-size and source-distance independence of the relative axial profile of the DAP as function of the thickness of a pre-absorber or of the depth in a phantom. For narrow-beam treatment planning in IMRT, the DAP is combined with the energy- and field size-dependent relative lateral dose distribution which is represented, for example, by a Gaussian convolution kernel. Another useful feature of the DAP is the possibility of its direct control during patient irradiation by means of an on-line monitor with spatial resolution, arranged in the accessory holder.
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