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Zarrini-Monfared Z, Karbasi S, Zamani A, Mosleh-Shirazi MA. Full modulation transfer functions of thick parallel- and focused-element scintillator arrays obtained by a Monte Carlo optical transport model. Med Phys 2023. [PMID: 36779548 DOI: 10.1002/mp.16306] [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: 06/12/2022] [Revised: 01/28/2023] [Accepted: 01/28/2023] [Indexed: 02/14/2023] Open
Abstract
BACKGROUND Arrays of thick segmented crystalline scintillators are useful x-ray converters for image-guided radiation therapy using electronic portal imaging (EPI) and megavoltage cone-beam computed tomography (MV-CBCT). Ionizing-radiation-only simulations previously showed relatively low modulation transfer function (MTF) in parallel-element arrays because of beam divergence. Hence, a focused-element geometry (matching the beam divergence) has been proposed. The "full" (ionizing and optical) MTF performance of such a focused geometry compared to its radiation-only MTF has, however, not been fully investigated. PURPOSE To study the full MTF performance of such arrays in a more realistic situation in which optical characteristics are also included using an in-house detector model that supports light transport, and quantify the errors in MTF estimation when the optical stage is ignored. METHODS First, radiation (x-ray and electron) transport was simulated. Then, transport of the generated optical photons was modeled using ScintSim2, an optical Monte Carlo (MC) code developed in MATLAB for simulation of two-dimensional (2D) parallel- and focused-element scintillator arrays. The full-MTF responses of focused- and parallel-element geometries, for a large array of 3 × 3 mm2 CsI:Tl detector elements of 10, 40, and 60 mm thicknesses, were examined. For each configuration, a composite line spread function (LSF) was calculated to obtain the MTF. RESULTS At the Nyquist frequency, for 10 mm-thick central elements and 60 mm-thick peripheral parallel elements, full-MTF exhibited a drop of up to 15 and 79 times, respectively, compared with radiation-only MTF. This was found to be partly attributable to the angular distribution of the light emerging from the detector-element exit face and the dependence on its aspect ratio, since the light exiting thicker scintillators exhibited a more forward-directed distribution. Focused elements provided an increase of up to nine times in peripheral-area full MTF values. CONCLUSIONS Full MTF was up to 79 times lower than radiation-only MTF. Focused arrays preserved full MTF by up to nine times compared to parallel elements. The differences in the results obtained with and without inclusion of optical photons emphasize the need to include light transport when optimizing thick segmented scintillation detectors. Besides their application in detector optimization for radiotherapy megavoltage photon imaging, these findings can also be useful for other segmented-scintillator-based imaging systems, for example, in nuclear medicine, or in 2D detection systems for quality assurance of MR-linacs.
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Affiliation(s)
- Zinat Zarrini-Monfared
- Department of Medical Physics and Engineering, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Sareh Karbasi
- Physics Unit, Department of Radio-oncology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Ali Zamani
- Department of Medical Physics and Engineering, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Mohammad Amin Mosleh-Shirazi
- Physics Unit, Department of Radio-oncology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.,Ionizing and Non-Ionizing Radiation Protection Research Center (INIRPRC), School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
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2
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Park H, Paganetti H, Schuemann J, Jia X, Min CH. Monte Carlo methods for device simulations in radiation therapy. Phys Med Biol 2021; 66:10.1088/1361-6560/ac1d1f. [PMID: 34384063 PMCID: PMC8996747 DOI: 10.1088/1361-6560/ac1d1f] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 08/12/2021] [Indexed: 11/12/2022]
Abstract
Monte Carlo (MC) simulations play an important role in radiotherapy, especially as a method to evaluate physical properties that are either impossible or difficult to measure. For example, MC simulations (MCSs) are used to aid in the design of radiotherapy devices or to understand their properties. The aim of this article is to review the MC method for device simulations in radiation therapy. After a brief history of the MC method and popular codes in medical physics, we review applications of the MC method to model treatment heads for neutral and charged particle radiation therapy as well as specific in-room devices for imaging and therapy purposes. We conclude by discussing the impact that MCSs had in this field and the role of MC in future device design.
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Affiliation(s)
- Hyojun Park
- Department of Radiation Convergence Engineering, Yonsei University, Wonju, Republic of Korea
| | - Harald Paganetti
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States of America
| | - Jan Schuemann
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States of America
| | - Xun Jia
- Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX 75235, United States of America
| | - Chul Hee Min
- Department of Radiation Convergence Engineering, Yonsei University, Wonju, Republic of Korea
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3
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Park H, Paganetti H, Schuemann J, Jia X, Min CH. Monte Carlo methods for device simulations in radiation therapy. Phys Med Biol 2021. [PMID: 34384063 DOI: 10.1088/1361-6560/ac1d1f.10.1088/1361-6560/ac1d1f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Monte Carlo (MC) simulations play an important role in radiotherapy, especially as a method to evaluate physical properties that are either impossible or difficult to measure. For example, MC simulations (MCSs) are used to aid in the design of radiotherapy devices or to understand their properties. The aim of this article is to review the MC method for device simulations in radiation therapy. After a brief history of the MC method and popular codes in medical physics, we review applications of the MC method to model treatment heads for neutral and charged particle radiation therapy as well as specific in-room devices for imaging and therapy purposes. We conclude by discussing the impact that MCSs had in this field and the role of MC in future device design.
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Affiliation(s)
- Hyojun Park
- Department of Radiation Convergence Engineering, Yonsei University, Wonju, Republic of Korea
| | - Harald Paganetti
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States of America
| | - Jan Schuemann
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States of America
| | - Xun Jia
- Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX 75235, United States of America
| | - Chul Hee Min
- Department of Radiation Convergence Engineering, Yonsei University, Wonju, Republic of Korea
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Jacobson MW, Lehmann M, Huber P, Wang A, Myronakis M, Shi M, Ferguson D, Valencia-Lozano I, Hu YH, Baturin P, Harris T, Fueglistaller R, Williams C, Morf D, Berbeco R. Abbreviated on-treatment CBCT using roughness penalized mono-energization of kV-MV data and a multi-layer MV imager. Phys Med Biol 2021; 66:10.1088/1361-6560/abddd2. [PMID: 33472189 PMCID: PMC11103584 DOI: 10.1088/1361-6560/abddd2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 01/20/2021] [Indexed: 11/11/2022]
Abstract
Simultaneous acquisition of cone beam CT (CBCT) projections using both the kV and MV imagers of an image guided radiotherapy system reduces set-up scan times-a benefit to lung cancer radiation oncology patients-but increases noise in the 3D reconstruction. In this article, we present a kV-MV scan time reduction technique that uses two noise-reducing measures to achieve superior performance. The first is a high-DQE multi-layer MV imager prototype. The second is a beam hardening correction algorithm which combines poly-energetic modeling with edge-preserving, regularized smoothing of the projections. Performance was tested in real acquisitions of the Catphan 604 and a thorax phantom. Percent noise was quantified from voxel values in a soft tissue volume of interest (VOI) while edge blur was quantified from a VOI straddling a boundary between air and soft material. Comparisons in noise/resolution performance trade-off were made between our proposed approach, a dose-equivalent kV-only scan, and a kV-MV reconstruction technique previously published by Yinet al(2005Med. Phys.329). The proposed technique demonstrated lower noise as a function of spatial resolution than the baseline kV-MV method, notably a 50% noise reduction at typical edge blur levels. Our proposed method also exhibited fainter non-uniformity artifacts and in some cases superior contrast. Overall, we find that the combination of a multi-layer MV imager, acquiring at a LINAC source energy of 2.5 MV, and a denoised beam hardening correction algorithm enables noise, resolution, and dose performance comparable to standard kV-imager only set-up CBCT, but with nearly half the gantry rotation time.
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Affiliation(s)
- Matthew W Jacobson
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, 02115, United States of America
| | | | - Pascal Huber
- Varian Medical Systems, Baden-Dattwil, CH-5405, Switzerland
| | - Adam Wang
- Varian Medical Systems, Palo Alto, CA, 94304-1030, United States of America
| | - Marios Myronakis
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, 02115, United States of America
| | - Mengying Shi
- Medical Physics Program, Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, MA 01854, United States of America
| | - Dianne Ferguson
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, 02115, United States of America
| | - Ingrid Valencia-Lozano
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, 02115, United States of America
| | - Yue-Houng Hu
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, 02115, United States of America
| | - Paul Baturin
- Varian Medical Systems, Palo Alto, CA, 94304-1030, United States of America
| | - Tom Harris
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, 02115, United States of America
| | | | - Christopher Williams
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, 02115, United States of America
| | - Daniel Morf
- Varian Medical Systems, Baden-Dattwil, CH-5405, Switzerland
| | - Ross Berbeco
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, 02115, United States of America
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Valencia Lozano I, Shi M, Myronakis M, Baturin P, Fueglistaller R, Huber P, Lehmann M, Morf D, Ferguson D, Jacobson MW, Harris T, Berbeco RI, Williams CL. Frequency-dependent optimal weighting approach for megavoltage multilayer imagers. Phys Med Biol 2021; 66. [PMID: 33503603 DOI: 10.1088/1361-6560/abe051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 01/27/2021] [Indexed: 11/12/2022]
Abstract
Multi-layer imaging (MLI) devices improve the detective quantum efficiency (DQE) while maintaining the spatial resolution of conventional mega-voltage (MV) x-ray detectors for applications in radiotherapy. To date, only MLIs with identical detector layers have been explored. However, it may be possible to instead use different scintillation materials in each layer to improve the final image quality. To this end, we developed and validated a method for optimally combining the individual images from each layer of MLI devices that are built with heterogeneous layers. Two configurations were modeled within the GATE Monte Carlo package by stacking different layers of a terbium doped gadolinium oxysulfide Gd2O2S:Tb (GOS) phosphor and a LKH-5 glass scintillator. Detector response was characterized in terms of the modulation transfer function (MTF), normalized noise power spectrum (NNPS) and DQE. Spatial frequency-dependent weighting factors were then analytically derived for each layer such that the total DQE of the summed combination image would be maximized across all spatial modes. The final image is obtained as the weighted sum of the sub-images from each layer. Optimal weighting factors that maximize the DQE were found to be the quotient of MTF and NNPS of each layer in the heterogeneous MLI detector. Results validated the improvement of the DQE across the entire frequency domain. For the LKH-5 slab configuration, DQE(0) increases between 2%-3% (absolute), while the corresponding improvement for the LKH-5 pixelated configuration was 7%. The performance of the weighting method was quantitatively evaluated with respect to spatial resolution, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of simulated planar images of phantoms at 2.5 and 6 MV. The line pair phantom acquisition exhibited a twofold increase in CNR and SNR, however MTF was degraded at spatial frequencies greater than 0.2 lp mm-1. For the Las Vegas phantom, the weighting improved the CNR by around 30% depending on the contrast region while the SNR values are higher by a factor of 2.5. These results indicate that the imaging performance of MLI systems can be enhanced using the proposed frequency-dependent weighting scheme. The CNR and SNR of the weighted combined image are improved across all spatial scales independent of the detector combination or photon beam energy.
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Affiliation(s)
- Ingrid Valencia Lozano
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, United States of America
| | - Mengying Shi
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, United States of America.,Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, MA, United States of America
| | - Marios Myronakis
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, United States of America
| | - Paul Baturin
- Varian Medical Systems, Palo Alto, CA, United States of America
| | | | | | | | | | - Dianne Ferguson
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, United States of America
| | - Matthew W Jacobson
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, United States of America
| | - Thomas Harris
- Varian Medical Systems, Palo Alto, CA, United States of America
| | - Ross I Berbeco
- Varian Medical Systems, Palo Alto, CA, United States of America
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Myronakis M, Huber P, Lehmann M, Fueglistaller R, Jacobson M, Hu Y, Baturin P, Wang A, Shi M, Harris T, Morf D, Berbeco R. Low‐dose megavoltage cone‐beam computed tomography using a novel multi‐layer imager (MLI). Med Phys 2020; 47:1827-1835. [DOI: 10.1002/mp.14017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 01/06/2020] [Accepted: 01/07/2020] [Indexed: 12/27/2022] Open
Affiliation(s)
- Marios Myronakis
- Department of Radiation Oncology Dana Farber/Brigham and Women's Cancer Center Harvard Medical School Boston MA 02115USA
| | | | | | | | - Matthew Jacobson
- Department of Radiation Oncology Dana Farber/Brigham and Women's Cancer Center Harvard Medical School Boston MA 02115USA
| | - Yue‐Houng Hu
- Department of Radiation Oncology Dana Farber/Brigham and Women's Cancer Center Harvard Medical School Boston MA 02115USA
| | - Paul Baturin
- Varian Medical Systems Palo Alto CA 94304‐1030USA
| | - Adam Wang
- Varian Medical Systems Palo Alto CA 94304‐1030USA
- Radiological Sciences Laboratory Stanford University Stanford CA 94305USA
| | - Mengying Shi
- Department of Radiation Oncology Dana Farber/Brigham and Women's Cancer Center Harvard Medical School Boston MA 02115USA
- Department of Radiation Oncology University of Massachusetts Lowell MA USA
| | - Thomas Harris
- Department of Radiation Oncology Dana Farber/Brigham and Women's Cancer Center Harvard Medical School Boston MA 02115USA
| | - Daniel Morf
- Varian Medical Systems Baden CH‐5405Switzerland
| | - Ross Berbeco
- Department of Radiation Oncology Dana Farber/Brigham and Women's Cancer Center Harvard Medical School Boston MA 02115USA
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Hu YH, Shedlock D, Wang A, Rottmann J, Baturin P, Myronakis M, Huber P, Fueglistaller R, Shi M, Morf D, Star-Lack J, Berbeco RI. Characterizing a novel scintillating glass for application to megavoltage cone-beam computed tomography. Med Phys 2019; 46:1323-1330. [PMID: 30586163 DOI: 10.1002/mp.13355] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 12/10/2018] [Accepted: 12/16/2018] [Indexed: 01/19/2023] Open
Abstract
PURPOSE The purpose of this study was to evaluate the performance of a prototype electric portal imaging device (EPID) with a high detective quantum efficiency (DQE) scintillator, LKH-5. Specifically, image quality in context of both planar and megavoltage (MV) cone-beam computed tomography (CBCT) is analyzed. METHODS Planar image quality in terms of modulation transfer function (MTF), noise power spectrum (NPS), and DQE are measured and compared to an existing EPID (AS-1200) using the 6 MV beamline for a Varian TrueBeam linac. Imager performance is contextualized for three-dimensional (3D), MV-CBCT performance by measuring imager lag and analyzing the expected degradation of the DQE as a function of dose. Finally, comparisons between reconstructed images of the Catphan phantom in terms of qualitative quality and signal-difference-to-noise ratio (SDNR) are made for 6 MV images using both conventional and LKH-5 EPIDs as well as for the kilovoltage (kV) on-board imager (OBI). RESULTS Analysis of the NPS reveals linearity at all measured doses using the prototype LKH-5 detector. While the first zero of the MTF is much lower for the LKH-5 detector than the conventional EPID (0.6 cycles/mm vs 1.6 cycles/mm), the normalized NPS (NNPS) multiplied by total quanta (qNNPS) of the LKH-5 detector is roughly a factor of seven to eight times lower, yielding a DQE(0) of approximately 8%. First, second, and third frame lag were measured at approximately 23%, 5%, and 1%, respectively, although no noticeable image artifacts were apparent in reconstructed volumes. Analysis of low-dose performance reveals that DQE(0) remains at 80% of its maximum value at a dose as low as 7.5 × 10-6 MU. For a 400 projection technique, this represents a total scan dose of 0.0030 MU, suggesting that if imaging doses are increased to a value typical of kV-CBCT scans (~2.7 cGy), the LKH-5 detector will retain quantum noise limited performance. Finally, comparing Catphan scans, the prototype detector exhibits much lower image noise than the conventional EPID, resulting in improved small object representation. Furthermore, SDNR of H2 O and polystyrene cylinders improved from -1.95 and 2.94 to -15 and 18.7, respectively. CONCLUSIONS Imaging performance of the prototype LKH-5 detector was measured and analyzed for both planar and 3D contexts. Improving noise transfer of the detector results in concurrent improvement of DQE(0). For 3D imaging, temporal characteristics were adequate for artifact-free performance and at relevant doses, the detector retained quantum noise limited performance. Although quantitative MTF measurements suggest poorer resolution, small object representation of the prototype imager is qualitatively improved over the conventional detector due to the measured reduction in noise.
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Affiliation(s)
- Yue-Houng Hu
- Department of Radiation Oncology, Division of Medical Physics and Biophysics, Brigham and Women's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 02115, USA
| | | | - Adam Wang
- Varian Medical Systems, Palo Alto, CA, 94304-1030, USA
| | - Joerg Rottmann
- Department of Radiation Oncology, Division of Medical Physics and Biophysics, Brigham and Women's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 02115, USA
| | - Paul Baturin
- Varian Medical Systems, Palo Alto, CA, 94304-1030, USA
| | - Marios Myronakis
- Department of Radiation Oncology, Division of Medical Physics and Biophysics, Brigham and Women's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 02115, USA
| | - Pascal Huber
- Varian Medical Systems, CH-5405, Baden-Dattwil, Switzerland
| | | | - Mengying Shi
- University of Massachusetts Lowell, Lowell, MA, 01854, USA
| | - Daniel Morf
- Varian Medical Systems, CH-5405, Baden-Dattwil, Switzerland
| | | | - Ross I Berbeco
- Department of Radiation Oncology, Division of Medical Physics and Biophysics, Brigham and Women's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 02115, USA
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Hu YH, Jacobson MW, Shi M, Myronakis M, Wang A, Baturin P, Huber P, Fueglistaller R, Morf D, Star-Lack J, Berbeco RI. Feasibility of closed-MLC tracking using high sensitivity and multi-layer electronic portal imagers. Phys Med Biol 2018; 63:235030. [DOI: 10.1088/1361-6560/aaef60] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Liu B, Zygmanski P, Sajo E. Portal MV imaging with thin-film high-energy current X-ray detectors: A Monte Carlo study. Med Phys 2017; 44:6128-6137. [DOI: 10.1002/mp.12613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 09/03/2017] [Accepted: 09/23/2017] [Indexed: 11/09/2022] Open
Affiliation(s)
- Bo Liu
- Department of Physics and Applied Physics; Medical Physics Program; University of Massachusetts Lowell; Lowell MA USA
| | - Piotr Zygmanski
- Harvard Medical School; Dana Farber Cancer Institute; Brigham and Women's Hospital; Boston MA USA
| | - Erno Sajo
- Department of Physics and Applied Physics; Medical Physics Program; University of Massachusetts Lowell; Lowell MA USA
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Liu L, Antonuk LE, El-Mohri Y, Zhao Q, Jiang H. Theoretical investigation of the design and performance of a dual energy (kV and MV) radiotherapy imager. Med Phys 2015; 42:2072-84. [DOI: 10.1118/1.4915120] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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