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Choi JW, Choi JY, Jang H, Joo KK, Kim BC. Pixel Image Analysis and Its Application with an Alcohol-Based Liquid Scintillator for Particle Therapy. SENSORS (BASEL, SWITZERLAND) 2022; 22:4876. [PMID: 35808370 PMCID: PMC9269500 DOI: 10.3390/s22134876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/09/2022] [Accepted: 06/23/2022] [Indexed: 06/15/2023]
Abstract
We synthesized an alcohol-based liquid scintillator (AbLS), and we implemented an auxiliary monitoring system with short calibration intervals using AbLS for particle therapy. The commercial liquid scintillator used in previous studies did not allow the user to control the chemical ratio and its composition. In our study, the chemical ratio of AbLS was freely controlled by simultaneously mixing water and alcohol. To make an equivalent substance to the human body, 2-ethoxyethanol was used. There was no significant difference between AbLS and water in areal density. As an application of AbLS, the range was measured with AbLS using an electron beam in an image analysis that combined AbLS and a digital phone camera. Given a range-energy relationship for the electron expressed as areal density, the electron beam range (cm) in water can be easily estimated. To date, no literature report for the direct comparison of a pixel image analysis and Monte Carlo (MC) simulation has been published. Furthermore, optical tomography of the inverse problem was performed with AbLS and a mobile phone camera. Analyses of optical tomography images provide deeper insight into Radon transformation. In addition, the human phantom, which is difficult to compose with semiconductor diodes, was easily implemented as an image acquisition and analysis system.
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Affiliation(s)
- Ji-Won Choi
- Institute for Universe & Elementary Particles, Department of Physics, Chonnam National University, Yongbong-ro 77, Puk-gu, Gwangju 61186, Korea;
| | - Ji-Young Choi
- Department of Fire Safety, Seoyeong University, Seogang-ro 1, Puk-gu, Gwangju 61268, Korea;
| | - Hanil Jang
- Department of Fire Safety, Seoyeong University, Seogang-ro 1, Puk-gu, Gwangju 61268, Korea;
| | - Kyung-Kwang Joo
- Institute for Universe & Elementary Particles, Department of Physics, Chonnam National University, Yongbong-ro 77, Puk-gu, Gwangju 61186, Korea;
| | - Byoung-Chan Kim
- Medical Radiation, Wonkwang Health Science University, 514, Iksan-daero, Iksan-si 54538, Korea
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2
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Cloutier E, Beaulieu L, Archambault L. Deformable scintillation dosimeter: II. Real-time simultaneous measurements of dose and tracking of deformation vector fields. Phys Med Biol 2021; 66. [PMID: 34380121 DOI: 10.1088/1361-6560/ac1ca2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 08/11/2021] [Indexed: 12/29/2022]
Abstract
Anatomical motion and deformation pose challenges to the understanding of the delivered dose distribution during radiotherapy treatments. Hence, deformable image registration (DIR) algorithms are increasingly used to map contours and dose distributions from one image set to another. However, the lack of validation tools slows their clinical adoption, despite their commercial availability. This work presents a novel water-equivalent deformable dosimeter that simultaneously measures the dose distribution and tracks deformation vector fields (DVF). The dosimeter in made of an array of 19 scintillating fiber detectors embedded in a cylindrical elastomer matrix. It is imaged by two pairs of stereoscopic cameras tracking the position and angulation of the scintillators, while measuring the dose. The resulting system provides a precision of 0.3 mm on DVF measurements. The dosimeter was irradiated with 5 × 3, 4 × 3 and 3 × 3 cm26 MV photon beams in both fixed and deformed conditions. The measured DVF was compared to the one computed with a DIR algorithm (Plastimatch). The deviations between the computed and measured DVFs was below 1.5 mm. As for dose measurements, the dosimeter acquired the dose distribution in fixed and deformed conditions within 1% of the treatment planning system calculation and complementary dose validation using the Hyperscint dosimetry system. Using the demonstrated qualities of scintillating detectors, we developed a real-time, water-equivalent deformable dosimeter. Given it's sensor tracking position precision and dose measurements accuracy, the developed detector is a promising tools for the validation of DIR algorithms as well as dose distribution measurements under fixed and deformed conditions.
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Affiliation(s)
- E Cloutier
- Service de physique médicale et Axe Oncologie du Centre de recherche, CHU de Québec-Université Laval, Canada.,Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancer, Université Laval, Québec, Canada
| | - L Beaulieu
- Service de physique médicale et Axe Oncologie du Centre de recherche, CHU de Québec-Université Laval, Canada.,Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancer, Université Laval, Québec, Canada
| | - L Archambault
- Service de physique médicale et Axe Oncologie du Centre de recherche, CHU de Québec-Université Laval, Canada.,Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancer, Université Laval, Québec, Canada
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3
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Cloutier E, Archambault L, Beaulieu L. Deformable scintillation dosimeter I: challenges and implementation using computer vision techniques. Phys Med Biol 2021; 66. [PMID: 34380116 DOI: 10.1088/1361-6560/ac1ca1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 08/11/2021] [Indexed: 01/18/2023]
Abstract
Plastic scintillation detectors are increasingly used to measure dose distributions in the context of radiotherapy treatments. Their water-equivalence, real-time response and high spatial resolution distinguish them from traditional detectors, especially in complex irradiation geometries. Their range of applications could be further extended by embedding scintillators in a deformable matrix mimicking anatomical changes. In this work, we characterized signal variations arising from the translation and rotation of scintillating fibers with respect to a camera. Corrections are proposed using stereo vision techniques and two sCMOS complementing a CCD camera. The study was extended to the case of a prototype real-time deformable dosimeter comprising an array of 19 scintillating fibers. The signal to angle relationship follows a gaussian distribution (FWHM = 52°) whereas the intensity variation from radial displacement follows the inverse square law. Tracking the position and angle of the fibers enabled the correction of these spatial dependencies. The detecting system provides an accuracy and precision of respectively 0.08 mm and 0.3 mm on the position detection. This resulted in an uncertainty of 2° on the angle measurement. Displacing the dosimeter by ±3 cm in depth resulted in relative intensities of 100 ± 10% (mean ± standard deviation) to the reference position. Applying corrections reduced the variations thus resulting in relative intensities of 100 ± 1%. Similarly, for lateral displacements of ±3 cm, intensities went from 98 ± 3% to 100 ± 1% after the correction. Therefore, accurate correction of the signal collected by a camera imaging the output of scintillating elements in a 3D volume is possible. This work paves the way to the development of real-time scintillator-based deformable dosimeters.
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Affiliation(s)
- E Cloutier
- Service de physique médicale et Axe Oncologie du Centre de recherche, CHU de Québec-Université Laval, Canada.,Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancer, Université Laval, Québec, Canada
| | - L Archambault
- Service de physique médicale et Axe Oncologie du Centre de recherche, CHU de Québec-Université Laval, Canada.,Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancer, Université Laval, Québec, Canada
| | - L Beaulieu
- Service de physique médicale et Axe Oncologie du Centre de recherche, CHU de Québec-Université Laval, Canada.,Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancer, Université Laval, Québec, Canada
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5
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Nusrat H, Pang G, Ahmad SB, Keller B, Sarfehnia A. Quantifying the impact of lead doping on plastic scintillator response to radiation. Med Phys 2019; 46:4215-4223. [DOI: 10.1002/mp.13691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 05/03/2019] [Accepted: 06/16/2019] [Indexed: 11/08/2022] Open
Affiliation(s)
- Humza Nusrat
- Department of Physics Ryerson University 350 Victoria St. M5B 2K3 Toronto ON Canada
| | - Geordi Pang
- Department of Medical Physics Odette Cancer Center, Sunnybrook Health Sciences Center 2075 Bayview Ave. M4N 3M5 Toronto ON Canada
| | - Syed Bilal Ahmad
- Department of Medical Physics Odette Cancer Center, Sunnybrook Health Sciences Center 2075 Bayview Ave. M4N 3M5 Toronto ON Canada
| | - Brian Keller
- Department of Medical Physics Odette Cancer Center, Sunnybrook Health Sciences Center 2075 Bayview Ave. M4N 3M5 Toronto ON Canada
| | - Arman Sarfehnia
- Department of Medical Physics Odette Cancer Center, Sunnybrook Health Sciences Center 2075 Bayview Ave. M4N 3M5 Toronto ON Canada
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Delage MÈ, Lecavalier MÈ, Larivière D, Allen CN, Beaulieu L. Dosimetric properties of colloidal quantum dot-based systems for scintillation dosimetry. Phys Med Biol 2019; 64:095027. [PMID: 30884473 DOI: 10.1088/1361-6560/ab109b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Colloidal quantum dots (cQDs) are starting to be used in radiation detection, either combined with an organic fluorophore or used as a sole luminescent material. In the latter case, only few studies report on cQD-based detectors for medical applications, especially for scintillation dosimetry in radiation therapy. Moreover, most of these studies focus on the effects of radiation on cQD photoluminescence but do not look into the properties of the scintillation signal itself. The present article provides a study of those cQD scintillation properties not previously investigated including the linearity of the signal as a function of dose, the signal dose rate and beam energy dependencies. The latter was also characterized for the commercially available scintillating fiber BCF-60 and liquid scintillator Ultima Gold. CdSe multishell cQDs in two physical forms were used as a sensitive dosimeter volume: a cQD powder to constitute a fiber optic based dosimeter and cQD liquid dispersions to be volumetric dosimeters. The signal linearity was assessed with a R2 coefficient >0.999 over a clinically relevant dose range at kV and MV beam energies. The cQDs had a good overall dose rate independence, with a change from the relative dose of 1% at MV energies and 2% at kV energies, of their scintillation output when irradiated with an orthovoltage device and a linear accelerator. Regarding the beam energy dependence, the cQD powder had the highest dependence amongst all the scintillators compared, the 120 kVp light output being up to almost 4 times that of the 6 MV beam. The smallest effect of the beam energy was reported for the cQD alkylbenzene liquid dispersion, having a variation of light signal normalized to 6 MV of 15% that is even less than for BCF-60 and Ultima Gold.
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Affiliation(s)
- Marie-Ève Delage
- Département de Physique, de génie Physique et d'optique et Centre de Recherche sur le Cancer, Université Laval, Québec, QC, G1V 0A6, Canada. Centre de Recherche du CHU de Québec - Université Laval, CHU de Québec, Québec, QC, G1R 2J6, Canada
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Kron T, Lehmann J, Greer PB. Dosimetry of ionising radiation in modern radiation oncology. Phys Med Biol 2016; 61:R167-205. [DOI: 10.1088/0031-9155/61/14/r167] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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8
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Glaser AK, Andreozzi JM, Zhang R, Pogue BW, Gladstone DJ. Optical cone beam tomography of Cherenkov-mediated signals for fast 3D dosimetry of x-ray photon beams in water. Med Phys 2016; 42:4127-36. [PMID: 26133613 DOI: 10.1118/1.4922135] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To test the use of a three-dimensional (3D) optical cone beam computed tomography reconstruction algorithm, for estimation of the imparted 3D dose distribution from megavoltage photon beams in a water tank for quality assurance, by imaging the induced Cherenkov-excited fluorescence (CEF). METHODS An intensified charge-coupled device coupled to a standard nontelecentric camera lens was used to tomographically acquire two-dimensional (2D) projection images of CEF from a complex multileaf collimator (MLC) shaped 6 MV linear accelerator x-ray photon beam operating at a dose rate of 600 MU/min. The resulting projections were used to reconstruct the 3D CEF light distribution, a potential surrogate of imparted dose, using a Feldkamp-Davis-Kress cone beam back reconstruction algorithm. Finally, the reconstructed light distributions were compared to the expected dose values from one-dimensional diode scans, 2D film measurements, and the 3D distribution generated from the clinical Varian ECLIPSE treatment planning system using a gamma index analysis. A Monte Carlo derived correction was applied to the Cherenkov reconstructions to account for beam hardening artifacts. RESULTS 3D light volumes were successfully reconstructed over a 400 × 400 × 350 mm(3) volume at a resolution of 1 mm. The Cherenkov reconstructions showed agreement with all comparative methods and were also able to recover both inter- and intra-MLC leaf leakage. Based upon a 3%/3 mm criterion, the experimental Cherenkov light measurements showed an 83%-99% pass fraction depending on the chosen threshold dose. CONCLUSIONS The results from this study demonstrate the use of optical cone beam computed tomography using CEF for the profiling of the imparted dose distribution from large area megavoltage photon beams in water.
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Affiliation(s)
- Adam K Glaser
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755
| | | | - Rongxiao Zhang
- Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755
| | - Brian W Pogue
- Thayer School of Engineering and Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755
| | - David J Gladstone
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766
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Ingram WS, Robertson D, Beddar S. Calculations and measurements of the scintillator-to-water stopping power ratio of liquid scintillators for use in proton radiotherapy. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION A, ACCELERATORS, SPECTROMETERS, DETECTORS AND ASSOCIATED EQUIPMENT 2015; 776:15-20. [PMID: 25705066 PMCID: PMC4332394 DOI: 10.1016/j.nima.2014.12.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Liquid scintillators are a promising detector for high-resolution three-dimensional proton therapy dosimetry. Because the scintillator comprises both the active volume of the detector and the phantom material, an ideal scintillator will exhibit water equivalence in its radiological properties. One of the most fundamental of these is the scintillator's stopping power. The objective of this study was to compare calculations and measurements of scintillator-to-water stopping power ratios to evaluate the suitability of the liquid scintillators BC-531 and OptiPhase HiSafe 3 for proton dosimetry. We also measured the relative scintillation output of the two scintillators. Both calculations and measurements show that the linear stopping power of OptiPhase is significantly closer to water than that of BC-531. BC-531 has a somewhat higher scintillation output. OptiPhase can be mixed with water at high concentrations, which further improves its scintillator-to-water stopping power ratio. However, this causes the solution to become cloudy, which has a negative impact on the scintillation output and spatial resolution of the detector. OptiPhase is preferred over BC-531 for proton dosimetry because its density and scintillator-to-water stopping power ratio are more water equivalent.
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Affiliation(s)
- W. Scott Ingram
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX 77030, USA
| | - Daniel Robertson
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Sam Beddar
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX 77030, USA
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Hui C, Robertson D, Beddar S. 3D reconstruction of scintillation light emission from proton pencil beams using limited viewing angles-a simulation study. Phys Med Biol 2014; 59:4477-92. [PMID: 25054735 DOI: 10.1088/0031-9155/59/16/4477] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
An accurate and high-resolution quality assurance (QA) method for proton radiotherapy beams is necessary to ensure correct dose delivery to the target. Detectors based on a large volume of liquid scintillator have shown great promise in providing fast and high-resolution measurements of proton treatment fields. However, previous work with these detectors has been limited to two-dimensional measurements, and the quantitative measurement of dose distributions was lacking. The purpose of the current study is to assess the feasibility of reconstructing three-dimensional (3D) scintillation light distributions of spot scanning proton beams using a scintillation system. The proposed system consists of a tank of liquid scintillator imaged by charge-coupled device cameras at three orthogonal viewing angles. Because of the limited number of viewing angles, we developed a profile-based technique to obtain an initial estimate that can improve the quality of the 3D reconstruction. We found that our proposed scintillator system and profile-based technique can reconstruct a single energy proton beam in 3D with a gamma passing rate (3%/3 mm local) of 100.0%. For a single energy layer of an intensity modulated proton therapy prostate treatment plan, the proposed method can reconstruct the 3D light distribution with a gamma pass rate (3%/3 mm local) of 99.7%. In addition, we also found that the proposed method is effective in detecting errors in the treatment plan, indicating that it can be a very useful tool for 3D proton beam QA.
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Affiliation(s)
- CheukKai Hui
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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Gorjiara T, Hill R, Bosi S, Kuncic Z, Baldock C. Water equivalence of NIPAM based polymer gel dosimeters with enhanced sensitivity for x-ray CT. Radiat Phys Chem Oxf Engl 1993 2013. [DOI: 10.1016/j.radphyschem.2013.05.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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12
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Goulet M, Archambault L, Beaulieu L, Gingras L. 3D tomodosimetry using long scintillating fibers: A feasibility study. Med Phys 2013; 40:101703. [DOI: 10.1118/1.4819937] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Robertson D, Mirkovic D, Sahoo N, Beddar S. Quenching correction for volumetric scintillation dosimetry of proton beams. Phys Med Biol 2013; 58:261-73. [PMID: 23257200 PMCID: PMC3849813 DOI: 10.1088/0031-9155/58/2/261] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Volumetric scintillation dosimetry has the potential to provide fast, high-resolution, three-dimensional radiation dosimetry. However, scintillators exhibit a nonlinear response at the high linear energy transfer (LET) values characteristic of proton Bragg peaks. The purpose of this study was to develop a quenching correction method for volumetric scintillation dosimetry of proton beams. Scintillation light from a miniature liquid scintillator detector was measured along the central axis of a 161.6 MeV proton pencil beam. Three-dimensional dose and LET distributions were calculated for 85.6, 100.9, 144.9 and 161.6 MeV beams using a validated Monte Carlo model. LET values were also calculated using an analytical formula. A least-squares fit to the data established the empirical parameters of a quenching correction model. The light distribution in a tank of liquid scintillator was measured with a CCD camera at all four beam energies. The quenching model and LET data were used to correct the measured light distribution. The calculated and measured Bragg peak heights agreed within ±3% for all energies except 85.6 MeV, where the agreement was within ±10%. The quality of the quenching correction was poorer for sharp low-energy Bragg peaks because of blurring and detector size effects. The corrections performed using analytical LET values resulted in doses within 1% of those obtained using Monte Carlo LET values. The proposed method can correct for quenching with sufficient accuracy for dosimetric purposes. The required LET values may be computed effectively using Monte Carlo or analytical methods. Future detectors should improve blurring correction methods and optimize the pixel size to improve accuracy for low-energy Bragg peaks.
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Affiliation(s)
- Daniel Robertson
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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Glaser AK, Davis SC, Voigt WHA, Zhang R, Pogue BW, Gladstone DJ. Projection imaging of photon beams using Čerenkov-excited fluorescence. Phys Med Biol 2013; 58:601-19. [PMID: 23318469 DOI: 10.1088/0031-9155/58/3/601] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Full 3D beam profiling and quality assurance (QA) of therapeutic megavoltage linear accelerator (LINAC) x-ray photon beams is not routinely performed due to the slow point-by-point measurement nature of conventional scanning ionization chamber systems. In this study we explore a novel optical-based dose imaging approach using a standard commercial camera, water tank, and fluorescent dye, which when excited by the Čerenkov emission induced by the radiation beam, allows 2D projection imaging in a fast timeframe, potentially leading toward 3D tomographic beam profiling. Detailed analysis was carried out to optimize the imaging parameters in the experimental setup. The results demonstrate that the captured images are linear with delivered dose, independent of dose rate, and comparison of experimentally captured images to a reference dose distribution for a 4 × 4 cm(2) 6 MV x-ray photon beam yielded results with improved accuracy over a previous study which used direct imaging and Monte Carlo calibration of the Čerenkov emission itself. The agreement with the reference dose distribution was within 1-2% in the lateral direction, and ±3% in the depth direction. The study was restricted to single 2D image projection, with the eventual goal of creating full 3D profiles after tomographic reconstruction from multiple projections. Given the increasingly complex advances in radiation therapy, and the increased emphasis on patient-specific treatment plans, further refinement of the technique could prove to be an important tool for fast and robust QA of x-ray photon LINAC beams.
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Affiliation(s)
- Adam K Glaser
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA.
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Gorjiara T, Hill R, Kuncic Z, Bosi S, Davies JB, Baldock C. Radiological characterization and water equivalency of genipin gel for x-ray and electron beam dosimetry. Phys Med Biol 2011; 56:4685-99. [PMID: 21734335 DOI: 10.1088/0031-9155/56/15/004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The genipin radiochromic gel offers enormous potential as a three-dimensional dosimeter in advanced radiotherapy techniques. We have used several methods (including Monte Carlo simulation), to investigate the water equivalency of genipin gel by characterizing its radiological properties, including mass and electron densities, photon interaction cross sections, mass energy absorption coefficient, effective atomic number, collisional, radiative and total mass stopping powers and electron mass scattering power. Depth doses were also calculated for clinical kilovoltage and megavoltage x-ray beams as well as megavoltage electron beams. The mass density, electron density and effective atomic number of genipin were found to differ from water by less than 2%. For energies below 150 keV, photoelectric absorption cross sections are more than 3% higher than water due to the strong dependence on atomic number. Compton scattering and pair production interaction cross sections for genipin gel differ from water by less than 1%. The mass energy absorption coefficient is approximately 3% higher than water for energies <60 keV due to the dominance of photoelectric absorption in this energy range. The electron mass stopping power and mass scattering power differ from water by approximately 0.3%. X-ray depth dose curves for genipin gel agree to within 1% with those for water. Our results demonstrate that genipin gel can be considered water equivalent for kilovoltage and megavoltage x-ray beam dosimetry. For megavoltage electron beam dosimetry, however, our results suggest that a correction factor may be needed to convert measured dose in genipin gel to that of water, since differences in some radiological properties of up to 3% compared to water are observed. Our results indicate that genipin gel exhibits greater water equivalency than polymer gels and PRESAGE formulations.
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Affiliation(s)
- Tina Gorjiara
- Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006, Australia
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Lacroix F, Beddar AS, Guillot M, Beaulieu L, Gingras L. A design methodology using signal-to-noise ratio for plastic scintillation detectors design and performance optimization. Med Phys 2010; 36:5214-20. [PMID: 19994531 DOI: 10.1118/1.3231947] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The design of novel plastic scintillation detectors (PSDs) is impeded by the lack of a suitable framework to simulate and predict their performance. The authors propose to use the signal-to-noise ratio (SNR) to model the performance of PSDs that use charge-coupled devices (CCDs) as photodetectors. METHODS In PSDs using CCDs, the SNR is inversely related to the normalized standard deviation of the dose measurement. Thus, optimizing the SNR directly optimizes the system's precision. In this work, a model of SNR as a function of the system parameters is derived for optical fiber-based PSD systems. Furthermore, this proposed model is validated using experimental results. A formula for the efficiency of fiber coupling to CCDs is derived and used to simulate the performance of a PSD under varying magnifications. RESULTS The proposed model is shown to simulate the experimental performance of an actual PSD to a suitable degree of accuracy under various conditions. CONCLUSIONS The SNR constitutes a useful tool to simulate the dosimetric precision of PSDs. Using the SNR model, recommendations for the design and optimization of PSDs are provided. Using the same framework, recommendations for non-fiber-based PSDs are also provided.
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Affiliation(s)
- Frédéric Lacroix
- Département de Radio-Oncologie, Centre hospitalier de l'Université de Montéfal, 1560 Sherbrooke est, Montréal, Quebec H2L 4MI, Canada.
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Beddar S, Archambault L, Sahoo N, Poenisch F, Chen GT, Gillin MT, Mohan R. Exploration of the potential of liquid scintillators for real-time 3D dosimetry of intensity modulated proton beams. Med Phys 2009; 36:1736-43. [PMID: 19544791 DOI: 10.1118/1.3117583] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In this study, the authors investigated the feasibility of using a 3D liquid scintillator (LS) detector system for the verification and characterization of proton beams in real time for intensity and energy-modulated proton therapy. A plastic tank filled with liquid scintillator was irradiated with pristine proton Bragg peaks. Scintillation light produced during the irradiation was measured with a CCD camera. Acquisition rates of 20 and 10 frames per second (fps) were used to image consecutive frame sequences. These measurements were then compared to ion chamber measurements and Monte Carlo simulations. The light distribution measured from the images acquired at rates of 20 and 10 fps have standard deviations of 1.1% and 0.7%, respectively, in the plateau region of the Bragg curve. Differences were seen between the raw LS signal and the ion chamber due to the quenching effects of the LS and due to the optical properties of the imaging system. The authors showed that this effect can be accounted for and corrected by Monte Carlo simulations. The liquid scintillator detector system has a good potential for performing fast proton beam verification and characterization.
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Affiliation(s)
- Sam Beddar
- Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 94, Houston, Texas 77030, USA.
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Pönisch F, Archambault L, Briere TM, Sahoo N, Mohan R, Beddar S, Gillin MT. Liquid scintillator for 2D dosimetry for high-energy photon beams. Med Phys 2009; 36:1478-85. [PMID: 19544763 PMCID: PMC2736702 DOI: 10.1118/1.3106390] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Complex radiation therapy techniques require dosimetric verification of treatment planning and delivery. The authors investigated a liquid scintillator (LS) system for application for real-time high-energy photon beam dosimetry. The system was comprised of a transparent acrylic tank filled with liquid scintillating material, an opaque outer tank, and a CCD camera. A series of images was acquired when the tank with liquid scintillator was irradiated with a 6 MV photon beam, and the light data measured with the CCD camera were filtered to correct for scattering of the optical light inside the liquid scintillator. Depth-dose and lateral profiles as well as two-dimensional (2D) dose distributions were found to agree with results from the treatment planning system. Further, the corrected light output was found to be linear with dose, dose rate independent, and is robust for single or multiple acquisitions. The short time needed for image acquisition and processing could make this system ideal for fast verification of the beam characteristics of the treatment machine. This new detector system shows a potential usefulness of the LS for 2D QA.
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Affiliation(s)
- Falk Pönisch
- Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard., Unit 94, Houston, Texas 77030, USA
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Nowotny R, Taubeck A. A method for the production of composite scintillators for dosimetry in diagnostic radiology. Phys Med Biol 2009; 54:1457-68. [DOI: 10.1088/0031-9155/54/6/005] [Citation(s) in RCA: 8] [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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Kirov AS, Piao JZ, Mathur NK, Miller TR, Devic S, Trichter S, Zaider M, Soares CG, LoSasso T. The three-dimensional scintillation dosimetry method: test for a106Ru eye plaque applicator. Phys Med Biol 2005; 50:3063-81. [PMID: 15972981 DOI: 10.1088/0031-9155/50/13/007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The need for fast, accurate and high resolution dosimetric quality assurance in radiation therapy has been outpacing the development of new and improved 2D and 3D dosimetry techniques. This paper summarizes the efforts to create a novel and potentially very fast, 3D dosimetry method based on the observation of scintillation light from an irradiated liquid scintillator volume serving simultaneously as a phantom material and as a dose detector medium. The method, named three-dimensional scintillation dosimetry (3DSD), uses visible light images of the liquid scintillator volume at multiple angles and applies a tomographic algorithm to a series of these images to reconstruct the scintillation light emission density in each voxel of the volume. It is based on the hypothesis that with careful design and data processing, one can achieve acceptable proportionality between the local light emission density and the locally absorbed dose. The method is applied to a Ru-106 eye plaque immersed in a 16.4 cm3 liquid scintillator volume and the reconstructed 3D dose map is compared along selected profiles and planes with radiochromic film and diode measurements. The comparison indicates that the 3DSD method agrees, within 25% for most points or within approximately 2 mm distance to agreement, with the relative radiochromic film and diode dose distributions in a small (approximately 4.5 mm high and approximately 12 mm diameter) volume in the unobstructed, high gradient dose region outside the edge of the plaque. For a comparison, the reproducibility of the radiochromic film results for our measurements ranges from 10 to 15% within this volume. At present, the 3DSD method is not accurate close to the edge of the plaque, and further than approximately 10 mm (<10% central axis depth dose) from the plaque surface. Improvement strategies, considered important to provide a more accurate quick check of the dose profiles in 3D for brachytherapy applicators, are discussed.
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Affiliation(s)
- A S Kirov
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
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Abstract
The use of ionization chambers in diagnostic radiology is not feasible in measurement situations requiring small and robust dose sensors. The composition of LiF:W developed as a scintillator for the measurement of thermal neutrons seems profitable for an application in dosimetry of low-energy photons. Properties of a small LiF:W scintillator were determined with DV- and DH-standard radiation qualities. For a tube voltage range of 40 to 150 kV (corresponding to a HVL of 1.56 to 13.69 mm Al) a maximum variation in sensitivity of +/-13% was determined for a scintillator thickness of 3.7 mm. The scintillator signal was linear in a range from 6.6 mGy min(-1) to at least 13.7 Gy min(-1). Higher dose rates could not be obtained in the measurement setup. The temperature dependence of the luminescence response was found to decrease from +3.7% (at +2.5 degrees C) to -7.0% (at +45 degrees C) with respect to the luminescence response at 20 degrees C. LiF:W appears to be an interesting choice as a dosimetric scintillator in diagnostic radiology making immediate measurements of dose and dose rate with high spatial resolution feasible.
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Affiliation(s)
- R Nowotny
- Institute for Biomedical Engineering and Physics, Medical University Vienna, AKH-4L, A-1090 Vienna, Austria.
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