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Feasibility study of a chlorophyll dosimeter for high energy X-ray beam used in radiotherapy. J Radioanal Nucl Chem 2021. [DOI: 10.1007/s10967-021-08106-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Baumann KS, Kaupa S, Bach C, Engenhart-Cabillic R, Zink K. Monte Carlo calculation of perturbation correction factors for air-filled ionization chambers in clinical proton beams using TOPAS/GEANT. Z Med Phys 2021; 31:175-191. [PMID: 33775521 DOI: 10.1016/j.zemedi.2020.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 08/20/2020] [Accepted: 08/31/2020] [Indexed: 10/21/2022]
Abstract
INTRODUCTION Current dosimetry protocols for clinical protons using air-filled ionization chambers assume that the perturbation correction factor is equal to unity for all ionization chambers and proton energies. Since previous Monte Carlo based studies suggest that perturbation correction factors might be significantly different from unity this study aims to determine perturbation correction factors for six plane-parallel and four cylindrical ionization chambers in proton beams at clinical energies. MATERIALS AND METHODS The dose deposited in the air cavity of the ionization chambers was calculated with the help of the Monte Carlo code TOPAS/Geant4 while specific constructive details of the chambers were removed step by step. By comparing these dose values the individual perturbation correction factors pcel, pstem, psleeve, pwall, pcav⋅pdis as well as the total perturbation correction factor pQ were derived for typical clinical proton energies between 80 and 250MeV. RESULTS The total perturbation correction factor pQ was smaller than unity for almost every ionization chamber and proton energy and in some cases significantly different from unity (deviation larger than 1%). The maximum deviation from unity was 2.0% for cylindrical and 1.5% for plane-parallel ionization chambers. Especially the factor pwall was found to differ significantly from unity. It was shown that this is due to the fact that secondary particles, especially alpha particles and fragments, are scattered from the chamber wall into the air cavity resulting in an overresponse of the chamber. CONCLUSION Perturbation correction factors for ionization chambers in proton beams were calculated using Monte Carlo simulations. In contrast to the assumption of current dosimetry protocols the total perturbation correction factor pQ can be significantly different from unity. Hence, beam quality correction factors [Formula: see text] that are calculated with the help of perturbation correction factors that are assumed to be unity come with a corresponding additional uncertainty.
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Affiliation(s)
- Kilian-Simon Baumann
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany; Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany.
| | - Sina Kaupa
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Constantin Bach
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Rita Engenhart-Cabillic
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany
| | - Klemens Zink
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany; Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany; Frankfurt Institute of Advanced Studies - FIAS, Frankfurt, Germany
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Badano A, Kyprianou IS, Freed M, Jennings RJ, Sempau J. Effect of oblique X-ray incidence in flat-panel computed tomography of the breast. IEEE TRANSACTIONS ON MEDICAL IMAGING 2009; 28:696-702. [PMID: 19272986 DOI: 10.1109/tmi.2008.2010443] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We quantify the variation in resolution due to anisotropy caused by oblique X-ray incidence in indirect flat-panel detectors for computed tomography breast imaging systems. We consider a geometry and detector type utilized in breast computed tomography (CT) systems currently being developed. Our methods rely on mantis, a combined X-ray, electron, and optical Monte Carlo transport open source code. The physics models are the most accurate available in general-purpose Monte Carlo packages in the diagnostic energy range. We consider maximum-obliquity angles of 10 ( degrees ) and 13 ( degrees ) at the centers of the 30 and 40 cm detector edges, respectively, and 16 ( degrees ) at the corner of the detector. Our results indicate that blur is asymmetric and that the resolution properties vary significantly with the angle (or location) of incidence. Our results suggest that the asymmetry can be as high as a factor of 2.6 between orthogonal directions. Anisotropy maps predicted by mantis provide an understanding of the effect that such variations have on the imaging system and allow more accurate modeling and optimization of breast CT systems. These maps of anisotropy across the detector could lead to improved reconstruction and help motivate physics-based strategies for computer detection of breast lesions.
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Affiliation(s)
- Aldo Badano
- NIBIB/CDRH Laboratory for the Assessment of Medical Imaging Systems, Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, US FDA, Silver Spring, MD 20993 USA.
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Sterpin E, Salvat F, Cravens R, Ruchala K, Olivera GH, Vynckier S. Monte Carlo simulation of helical tomotherapy with PENELOPE. Phys Med Biol 2008; 53:2161-80. [DOI: 10.1088/0031-9155/53/8/011] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Badano A, Kyprianou IS, Jennings RJ, Sempau J. Anisotropic imaging performance in breast tomosynthesis. Med Phys 2008; 34:4076-91. [PMID: 18074617 DOI: 10.1118/1.2779943] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We describe the anisotropy in imaging performance caused by oblique x-ray incidence in indirect detectors for breast tomosynthesis based on columnar scintillator screens. We use MANTIS, a freely available combined x-ray, electron, and optical Monte Carlo transport package which models the indirect detection processes in columnar screens, interaction by interaction. The code has been previously validated against published optical distributions. In this article, initial validation results are provided concerning the blur for particular designs of phosphor screens for which some details with respect to the columnar geometry are available from scanning electron microscopy. The polyenergetic x-ray spectrum utilized comes from a database of experimental data for three different anode/filter/kVp combinations: Mo/Mo at 28 kVp, Rh/Rh at 28 kVp, and W/Al at 42 kVp. The x-ray spectra were then filtered with breast tissue (3, 4, and 6 cm thickness), compression paddle, and support base, according to the oblique paths determined by the incidence angle. The composition of the breast tissue was 50%/50% adipose/glandular tissue mass ratio. Results are reported on the pulse-height statistics of the light output and on spatial blur, expressed as the response of the detector to a pencil beam with a certain incidence angle. Results suggest that the response is nonsymmetrical and that the resolution properties of a tomosynthesis system vary significantly with the angle of x-ray incidence. In contrast, it is found that the noise due to the variability in the number of light photons detected per primary x-ray interaction changes only a few percent. The anisotropy in the response is not less in screens with absorptive backings while the noise introduced by variations in the depth-dependent light output and optical transport is larger. The results suggest that anisotropic imaging performance across the detector area can be incorporated into reconstruction algorithms for improving the image quality of breast tomosynthesis. This study also demonstrates that the assessment of image quality of breast tomosynthesis systems requires a more complete description of the detector response beyond local, center measurements of resolution and noise that assume some degree of symmetry in the detector performance.
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Affiliation(s)
- Aldo Badano
- Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland 20993, USA.
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Badano A, Kyprianou IS, Sempau J. Anisotropic imaging performance in indirect x-ray imaging detectors. Med Phys 2006; 33:2698-713. [PMID: 16967568 DOI: 10.1118/1.2208925] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
We report on the variability in imaging system performance due to oblique x-ray incidence, and the associated transport of quanta (both x rays and optical photons) through the phosphor, in columnar indirect digital detectors. The analysis uses MANTIS, a combined x-ray, electron, and optical Monte Carlo transport code freely available. We describe the main features of the simulation method and provide some validation of the phosphor screen models considered in this work. We report x-ray and electron three-dimensional energy deposition distributions and point-response functions (PRFs), including optical spread in columnar phosphor screens of thickness 100 and 500 microm, for 19, 39, 59, and 79 keV monoenergetic x-ray beams incident at 0 degrees, 10 degrees, and 15 degrees. In addition, we present pulse-height spectra for the same phosphor thickness, x-ray energies, and angles of incidence. Our results suggest that the PRF due to the phosphor blur is highly nonsymmetrical, and that the resolution properties of a columnar screen in a tomographic, or tomosynthetic imaging system varies significantly with the angle of x-ray incidence. Moreover, we find that the noise due to the variability in the number of light photons detected per primary x-ray interaction, summarized in the information or Swank factor, is somewhat independent of thickness and incidence angle of the x-ray beam. Our results also suggest that the anisotropy in the PRF is not less in screens with absorptive backings, while the noise introduced by variations in the gain and optical transport is larger. Predictions from MANTIS, after additional validation, can provide the needed understanding of the extent of such variations, and eventually, lead to the incorporation of the changes in imaging performance with incidence angle into the reconstruction algorithms for volumetric x-ray imaging systems.
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Affiliation(s)
- Aldo Badano
- Division of Imaging and Applied Mathematics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, U.S. Food & Drug Administration, 12720 Twinbrook Parkway, Rockville, Maryland 20857, USA.
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Badano A, Sempau J. MANTIS: combined x-ray, electron and optical Monte Carlo simulations of indirect radiation imaging systems. Phys Med Biol 2006; 51:1545-61. [PMID: 16510962 DOI: 10.1088/0031-9155/51/6/013] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We describe MANTIS (Monte carlo x-rAy electroN opTical Imaging Simulation), a tool for simulating imaging systems that tracks x-rays, electrons and optical photons in arbitrary materials and complex geometries. The x-ray and electron transport and involved physics models are from the PENELOPE package, and the optical transport and corresponding physics models are from DETECT-II and include Fresnel refraction and reflection at material boundaries, bulk absorption and scattering. Complex geometries can be handled with the aid of the geometry routines included in PENELOPE. When x-rays or electrons interact and deposit energy in the scintillator, the code generates a number of optical quanta according to a user-selected model for the conversion process. The optical photons are then tracked until they reach an absorption event, which in some cases contributes to the output signal, or escape from the geometry. We demonstrate the capabilities of this new tool with respect to the statistics of the optical signal detected and to the three-dimensional point-response functions corresponding to columnar phosphor screens.
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Affiliation(s)
- Aldo Badano
- NIBIB/CDRH Laboratory for the Assessment of Medical Imaging Systems, 12720 Twinbrook Parkway, HFZ-142, Rockville, MD 20857, USA.
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Sempau J, Andreo P, Aldana J, Mazurier J, Salvat F. Electron beam quality correction factors for plane-parallel ionization chambers: Monte Carlo calculations using the PENELOPE system. Phys Med Biol 2004; 49:4427-44. [PMID: 15509075 DOI: 10.1088/0031-9155/49/18/016] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Simulations of three plane-parallel ionization chambers have been used to determine directly the chamber- and quality-dependent factors fc,Q, instead of the product (Sw,air p)Q, and kQ,Q0 (or kQ,Q,int) for a broad range of electron beam qualities (4-20 MeV) using divergent monoenergetic beams and phase-space data from two accelerators. An original calculation method has been used which circumvents the weakness of the so far assumed independence between stopping-power ratios and perturbation factors. Very detailed descriptions of the geometry and materials of the chambers have been obtained from the manufacturers, and prepared as input to the PENELOPE 2003 Monte Carlo system using a computer code that includes correlated sampling and particle splitting. Values of the beam quality factors have been determined for the case of an electron reference beam. The calculated values have been compared with those in the IAEA TRS-398 dosimetry protocol and the differences analysed. The results for a NACP-02 chamber show remarkably good agreement with TRS-398 at high electron beam qualities but differ slightly at low energies. Arguments to explain the differences include questioning the undemonstrated assumption that the NACP is a 'perturbation-free' chamber even at very low electron beam energies. Results for Wellhöfer PPC-40 and PPC-05 chambers cannot be compared with data from others for these chambers because no calculations or reliable experimental data exist. It has been found that the results for the PPC-40 are very close to those of a Roos chamber, but the values for the PPC-05 are considerably different from those of a Markus chamber, and rather approach those of a Roos chamber. Results for monoenergetic electrons and accelerator phase-space data have been compared to assess the need for detailed and costly simulations, finding very small differences. This questions the emphasis given in recent years to the use of 'realistic' source data for accurate electron beam dosimetry.
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Affiliation(s)
- Josep Sempau
- Institut de Tècniques Enèrgetiques, Universitat Politècnica de Catalunya, Barcelona, Spain
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Ye SJ, Brezovich IA, Pareek P, Naqvi SA. Benchmark of PENELOPE code for low-energy photon transport: dose comparisons with MCNP4 and EGS4. Phys Med Biol 2004; 49:387-97. [PMID: 15012008 DOI: 10.1088/0031-9155/49/3/003] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The expanding clinical use of low-energy photon emitting 125I and 103Pd seeds in recent years has led to renewed interest in their dosimetric properties. Numerous papers pointed out that higher accuracy could be obtained in Monte Carlo simulations by utilizing newer libraries for the low-energy photon cross-sections, such as XCOM and EPDL97. The recently developed PENELOPE 2001 Monte Carlo code is user friendly and incorporates photon cross-section data from the EPDL97. The code has been verified for clinical dosimetry of high-energy electron and photon beams, but has not yet been tested at low energies. In the present work, we have benchmarked the PENELOPE code for 10-150 keV photons. We computed radial dose distributions from 0 to 10 cm in water at photon energies of 10-150 keV using both PENELOPE and MCNP4C with either DLC-146 or DLC-200 cross-section libraries, assuming a point source located at the centre of a 30 cm diameter and 20 cm length cylinder. Throughout the energy range of simulated photons (except for 10 keV), PENELOPE agreed within statistical uncertainties (at worst +/- 5%) with MCNP/DLC-146 in the entire region of 1-10 cm and with published EGS4 data up to 5 cm. The dose at 1 cm (or dose rate constant) of PENELOPE agreed with MCNP/DLC-146 and EGS4 data within approximately +/- 2% in the range of 20-150 keV, while MCNP/DLC-200 produced values up to 9% lower in the range of 20-100 keV than PENELOPE or the other codes. However, the differences among the four datasets became negligible above 100 keV.
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Affiliation(s)
- Sung-Joon Ye
- Department of Radiation Oncology, University of Alabama School of Medicine, 1824 6th Avenue South, Birmingham, AL 35294, USA.
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Asenjo J, Fernández-Varea JM, Sánchez-Reyes A. Characterization of a high-dose-rate 90Sr-90Y source for intravascular brachytherapy by using the Monte Carlo code PENELOPE. Phys Med Biol 2002; 47:697-711. [PMID: 11931465 DOI: 10.1088/0031-9155/47/5/301] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Radiation treatment with catheter-based beta-emitter sources is currently under clinical trial to prevent restenosis. In the present paper, we address the characterization of the high-dose-rate 90Sr-90Y seeds of the Beta-Cath system supplied by Novoste Corporation, one of the commercially available sources for intravascular brachytherapy. The Monte Carlo code PENELOPE has been used to simulate the transport of electrons emitted by the encapsulated 90Sr-90Y seeds. The calculated radial dose function and anisotropy function for a single seed in water are compared with simulation results from other authors. Regarding g(r), the present result lies between the ITS3 and EGS4 curves, being somewhat closer to ITS3, while in the case of F(r, theta) some differences appear for certain angular intervals and radial distances. In order to put the observed differences into perspective, we have calculated radial doses for point isotropic sources in water. Our results for 0.5 and 1 MeV electrons are in good agreement with simulations using EGSnrc, and an excellent agreement is obtained with ITS for point 90Sr-90Y emitters. Dose distributions in water are calculated for source 'trains' consisting of 1, 2, 3, 4, 5, 9 and 12 seeds. The dose at the source midplane is enhanced if the number of seeds is up to 4, and saturates for trains with 5 or more seeds. We also compare the dose distribution obtained by simply adding the contributions of individual seeds with the simulation of the complete source train. It is found that both calculation procedures yield essentially the same result for distances greater than about 2 mm. Finally, the contribution of bremsstrahlung photons to the dose is briefly analysed.
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Affiliation(s)
- J Asenjo
- Servicio de Oncología Radioterápica, Hospital Clínic de Barcelona, Spain
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