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Baghani HR, Andreoli S, Robatjazi M. On the measurement of scaling factors in the RW3 plastic phantom during high energy electron beam dosimetry. Phys Eng Sci Med 2023; 46:185-195. [PMID: 36593380 DOI: 10.1007/s13246-022-01209-0] [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: 08/02/2022] [Accepted: 12/05/2022] [Indexed: 01/04/2023]
Abstract
Ionometric electron dosimetry inside water-equivalent plastic phantoms demands special considerations including determination of depth scaling and fluence scaling factors (cpl and hpl) to shift from in-phantom measurements to those relevant to water. This study evaluates these scaling factors for RW3 slab phantom and also introduces a new coefficient, k(RW3), for direct conversion from RW3 measurements to water without involving scaling factors. The RW3 solid phantom developed by the PTW Company was used and the corresponding scaling factors including cpl, hpl, and k(RW3) were measured for conventional electron energies of 4, 6, 9, 12, and 16 MeV. Separate measurements were performed in water and the RW3 slab phantom using the Advanced Markus chamber. The validity of the reported scaling factors was confirmed by comparing the direct and indirect percentage depth dose (PDD) measurements in water and in the RW3 phantom. The cpl values for the RW3 phantom were respectively equal to 0.915, 0.927, 0.934, 0.937, and 0.937 for 4, 6, 9, 12, and 16 MeV electron energies. The hpl and k(RW3) values were dependent on the depth of investigation and electron energy. Application of the cpl-hpl factors and k(RW3) coefficients to measured data inside the RW3 can reliably reproduce the measured PDD curves in water. The mean difference between the PDDs measured directly and indirectly in water and in the RW3 phantom was less than 1.2% in both approaches for PDD conversion (cpl-hpl coupling and the use of k(RW3)). The measured scaling factors and k(RW3) coefficients are sufficiently relevant to mimic water-based dosimetry results through indirect measurements inside the RW3 slab phantom. Nevertheless, employing k(RW3) is more straightforward than the cpl-hpl approach because it does not involve scaling and it is also less time-consuming.
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Affiliation(s)
| | | | - Mostafa Robatjazi
- Medical Physics and Radiological Sciences Department, Sabzevar University of Medical Sciences, Sabzevar, Iran
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2
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Diamantopoulos S, Kantemiris I, Patatoukas G, Dilvoi M, Efstathopoulos E, Kouloulias V, Platoni K. Theoretical and experimental determination of scaling factors in electron dosimetry for 3D-printed polylactic acid. Med Phys 2018; 45:1708-1714. [DOI: 10.1002/mp.12790] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Revised: 12/28/2017] [Accepted: 01/16/2018] [Indexed: 11/11/2022] Open
Affiliation(s)
- Stefanos Diamantopoulos
- 2nd Department of Radiology; University General Hospital “Attikon”; National and Kapodistrian University of Athens; 1 Rimini Street 12462 Chaidari Greece
- Medical Physics Department; Metropolitan Hospital; 9 Ethnarchou Makariou & 1 E. Venizelou Streets 18547 Neo Faliro Greece
| | - Ioannis Kantemiris
- Medical Physics Department; Metropolitan Hospital; 9 Ethnarchou Makariou & 1 E. Venizelou Streets 18547 Neo Faliro Greece
| | - Georgios Patatoukas
- 2nd Department of Radiology; University General Hospital “Attikon”; National and Kapodistrian University of Athens; 1 Rimini Street 12462 Chaidari Greece
| | - Maria Dilvoi
- 2nd Department of Radiology; University General Hospital “Attikon”; National and Kapodistrian University of Athens; 1 Rimini Street 12462 Chaidari Greece
| | - Efstathios Efstathopoulos
- 2nd Department of Radiology; University General Hospital “Attikon”; National and Kapodistrian University of Athens; 1 Rimini Street 12462 Chaidari Greece
| | - Vassilis Kouloulias
- 2nd Department of Radiology; University General Hospital “Attikon”; National and Kapodistrian University of Athens; 1 Rimini Street 12462 Chaidari Greece
| | - Kalliopi Platoni
- 2nd Department of Radiology; University General Hospital “Attikon”; National and Kapodistrian University of Athens; 1 Rimini Street 12462 Chaidari Greece
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Gerbi BJ, Antolak JA, Deibel FC, Followill DS, Herman MG, Higgins PD, Huq MS, Mihailidis DN, Yorke ED, Hogstrom KR, Khan FM. Recommendations for clinical electron beam dosimetry: supplement to the recommendations of Task Group 25. Med Phys 2009; 36:3239-79. [PMID: 19673223 DOI: 10.1118/1.3125820] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The goal of Task Group 25 (TG-25) of the Radiation Therapy Committee of the American Association of.Physicists in Medicine (AAPM) was to provide a methodology and set of procedures for a medical physicist performing clinical electron beam dosimetry in the nominal energy range of 5-25 MeV. Specifically, the task group recommended procedures for acquiring basic information required for acceptance testing and treatment planning of new accelerators with therapeutic electron beams. Since the publication of the TG-25 report, significant advances have taken place in the field of electron beam dosimetry, the most significant being that primary standards laboratories around the world have shifted from calibration standards based on exposure or air kerma to standards based on absorbed dose to water. The AAPM has published a new calibration protocol, TG-51, for the calibration of high-energy photon and electron beams. The formalism and dosimetry procedures recommended in this protocol are based on the absorbed dose to water calibration coefficient of an ionization chamber at 60Co energy, N60Co(D,w), together with the theoretical beam quality conversion coefficient k(Q) for the determination of absorbed dose to water in high-energy photon and electron beams. Task Group 70 was charged to reassess and update the recommendations in TG-25 to bring them into alignment with report TG-51 and to recommend new methodologies and procedures that would allow the practicing medical physicist to initiate and continue a high quality program in clinical electron beam dosimetry. This TG-70 report is a supplement to the TG-25 report and enhances the TG-25 report by including new topics and topics that were not covered in depth in the TG-25 report. These topics include procedures for obtaining data to commission a treatment planning computer, determining dose in irregularly shaped electron fields, and commissioning of sophisticated special procedures using high-energy electron beams. The use of radiochromic film for electrons is addressed, and radiographic film that is no longer available has been replaced by film that is available. Realistic stopping-power data are incorporated when appropriate along with enhanced tables of electron fluence data. A larger list of clinical applications of electron beams is included in the full TG-70 report available at http://www.aapm.org/pubs/reports. Descriptions of the techniques in the clinical sections are not exhaustive but do describe key elements of the procedures and how to initiate these programs in the clinic. There have been no major changes since the TG-25 report relating to flatness and symmetry, surface dose, use of thermoluminescent dosimeters or diodes, virtual source position designation, air gap corrections, oblique incidence, or corrections for inhomogeneities. Thus these topics are not addressed in the TG-70 report.
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Affiliation(s)
- Bruce J Gerbi
- University of Minnesota, Minneapolis, Minnesota 55455, USA.
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4
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Araki F, Hanyu Y, Fukuoka M, Matsumoto K, Okumura M, Oguchi H. Monte Carlo calculations of correction factors for plastic phantoms in clinical photon and electron beam dosimetry. Med Phys 2009; 36:2992-3001. [PMID: 19673198 DOI: 10.1118/1.3151809] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The purpose of this study is to calculate correction factors for plastic water (PW) and plastic water diagnostic-therapy (PWDT) phantoms in clinical photon and electron beam dosimetry using the EGSnrc Monte Carlo code system. A water-to-plastic ionization conversion factor k(pl) for PW and PWDT was computed for several commonly used Farmer-type ionization chambers with different wall materials in the range of 4-18 MV photon beams. For electron beams, a depth-scaling factor c(pl) and a chamber-dependent fluence correction factor h(pl) for both phantoms were also calculated in combination with NACP-02 and Roos plane-parallel ionization chambers in the range of 4-18 MeV. The h(pl) values for the plane-parallel chambers were evaluated from the electron fluence correction factor phi(pl)w and wall correction factors P(wall,w) and P(wall,pl) for a combination of water or plastic materials. The calculated k(pl) and h(pl) values were verified by comparison with the measured values. A set of k(pl) values computed for the Farmer-type chambers was equal to unity within 0.5% for PW and PWDT in photon beams. The k(pl) values also agreed within their combined uncertainty with the measured data. For electron beams, the c(pl) values computed for PW and PWDT were from 0.998 to 1.000 and from 0.992 to 0.997, respectively, in the range of 4-18 MeV. The phi(pl)w values for PW and PWDT were from 0.998 to 1.001 and from 1.004 to 1.001, respectively, at a reference depth in the range of 4-18 MeV. The difference in P(wall) between water and plastic materials for the plane-parallel chambers was 0.8% at a maximum. Finally, h(pl) values evaluated for plastic materials were equal to unity within 0.6% for NACP-02 and Roos chambers. The h(pl) values also agreed within their combined uncertainty with the measured data. The absorbed dose to water from ionization chamber measurements in PW and PWDT plastic materials corresponds to that in water within 1%. Both phantoms can thus be used as a substitute for water for photon and electron dosimetry.
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Affiliation(s)
- Fujio Araki
- Department of Radiological Technology, Kumamoto University School of Health Sciences, 4-24-1, Kuhonji, Kumamoto 862-0976, Japan.
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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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Zink K, Wulff J. Positioning of a plane-parallel ionization chamber in clinical electron beams and the impact on perturbation factors. Phys Med Biol 2009; 54:2421-35. [DOI: 10.1088/0031-9155/54/8/011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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7
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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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8
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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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Araki F. Monte Carlo study of correction factors for the use of plastic phantoms in clinical electron dosimetry. Med Phys 2007; 34:4368-77. [DOI: 10.1118/1.2790840] [Citation(s) in RCA: 8] [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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10
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Assiamah M, Nam TL, Keddy RJ. Radiation doses from low energy X-ray beams measured with synthetic diamond compared with calculated values obtained from the PENELOPE Monte Carlo code. Appl Radiat Isot 2007; 65:952-8. [PMID: 17482827 DOI: 10.1016/j.apradiso.2007.01.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2006] [Revised: 12/11/2006] [Accepted: 01/29/2007] [Indexed: 11/18/2022]
Abstract
The utilization of a probe with synthetic diamond as the sensing material developed to measure radiation doses from mammography X-ray beams is described. The computer code system PENELOPE was used, with a geometry model simulating the experimental conditions, to compute the doses from the mammography X-ray beams to the diamond sensing material. The orientation of the diamond sensor to provide maximum absorption of the incident X-ray beam during exposure was also investigated using the PENELOPE code. The results from the theoretical model and experimental measurements are compared.
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Affiliation(s)
- M Assiamah
- Health Physics Unit, & FRD/NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
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11
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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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12
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Abstract
For over 50 years, electron beams have been an important modality for providing an accurate dose of radiation to superficial cancers and disease and for limiting the dose to underlying normal tissues and structures. This review looks at many of the important contributions of physics and dosimetry to the development and utilization of electron beam therapy, including electron treatment machines, dose specification and calibration, dose measurement, electron transport calculations, treatment and treatment-planning tools, and clinical utilization, including special procedures. Also, future changes in the practice of electron therapy resulting from challenges to its utilization and from potential future technology are discussed.
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Affiliation(s)
- Kenneth R Hogstrom
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001, USA.
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13
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McEwen MR, Niven D. Characterization of the phantom material Virtual Water™ in high-energy photon and electron beams. Med Phys 2006; 33:876-87. [PMID: 16696463 DOI: 10.1118/1.2174186] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The material Virtual Water has been characterized in photon and electron beams. Range-scaling factors and fluence correction factors were obtained, the latter with an uncertainty of around 0.2%. This level of uncertainty means that it may be possible to perform dosimetry in a solid phantom with an accuracy approaching that of measurements in water. Two formulations of Virtual Water were investigated with nominally the same elemental composition but differing densities. For photon beams neither formulation showed exact water equivalence-the water/Virtual Water dose ratio varied with the depth of measurement with a difference of over 1% at 10 cm depth. However, by using a density (range) scaling factor very good agreement (<0.2%) between water and Virtual Water at all depths was obtained. In the case of electron beams a range-scaling factor was also required to match the shapes of the depth dose curves in water and Virtual Water. However, there remained a difference in the measured fluence in the two phantoms after this scaling factor had been applied. For measurements around the peak of the depth-dose curve and the reference depth this difference showed some small energy dependence but was in the range 0.1%-0.4%. Perturbation measurements have indicated that small slabs of material upstream of a detector have a small (<0.1% effect) on the chamber reading but material behind the detector can have a larger effect. This has consequences for the design of experiments and in the comparison of measurements and Monte Carlo-derived values.
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Affiliation(s)
- M R McEwen
- Ionizing Radiation Standards, Institute for National Measurement Standards, National Research Council of Canada, Ottawa, Canada
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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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