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Jeong S, Kim CE, Kim C, Pak SI, An S, Cheon W, Shin D, Lim YK, Jeong JH, Kim H, Chung Y, Choi SH, Lee SB. Feasibility study for the development of multilayered solar cells for proton linear energy transfer depth profile measurement. Med Phys 2024. [PMID: 38828894 DOI: 10.1002/mp.17234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 05/09/2024] [Accepted: 05/10/2024] [Indexed: 06/05/2024] Open
Abstract
BACKGROUND Previous study proposed a method to measure linear energy transfer (LET) at specific points using the quenching magnitude of thin film solar cells. This study was conducted to propose a more advanced method for measuring the LET distribution. PURPOSE This study focuses on evaluating the feasibility of estimating the proton LET distribution in proton therapy. The feasibility of measuring the proton LET and dose distribution simultaneously using a single-channel configuration comprising two solar cells with distinct quenching constants is investigated with the objective of paving the way for enhanced proton therapy dosimetry. METHODS Two solar cells with different quenching constants were used to estimate the proton LET distribution. Detector characteristics (e.g., dose linearity and dose-rate dependency) of the solar cells were evaluated to assess their suitability for dosimetry applications. First, using a reference beam condition, the quenching constants of the two solar cells were determined according to the modified Birks equation. The signal ratios of the two solar cells were then evaluated according to proton LET in relation to the estimated quenching constants. The proton LET distributions of six test beams were obtained by measuring the signal ratios of the two solar cells at each depth, and the ratios were evaluated by comparing them with those calculated by Monte Carlo simulation. RESULTS The detector characterization of the two solar cells including dose linearity and dose-rate dependence affirmed their suitability for use in dosimetry applications. The maximum difference between the LET measured using the two solar cells and that calculated by Monte Carlo simulation was 2.34 keV/µm. In the case of the dose distribution measured using the method proposed in this study, the maximum difference between range measured using the proposed method and that measured using a multilayered ionization chamber was 0.7 mm. The expected accuracy of simultaneous LET and dose distribution measurement using the method proposed in this study were estimated to be 3.82%. The signal ratios of the two solar cells, which are related to quenching constants, demonstrated the feasibility of measuring LET and dose distribution simultaneously. CONCLUSION The feasibility of measuring proton LET and dose distribution simultaneously using two solar cells with different quenching constants was demonstrated. Although the method proposed in this study was evaluated using a single channel by varying the measuring depth, the results suggest that the proton LET and dose distribution can be simultaneously measured if the detector is configured in a multichannel form. We believe that the results presented in this study provide the envisioned transition to a multichannel configuration, with the promise of substantially advancing proton therapy's accuracy and efficacy in cancer treatment.
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Affiliation(s)
- Seonghoon Jeong
- Department of Neurosurgery, College of Medicine, Ilsan Paik Hospital, Inje University, Goyang, Republic of Korea
| | - Chae-Eon Kim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
- Department of Nuclear Engineering, Hanyang University, Seoul, Republic of Korea
| | - Chankyu Kim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Sang-Il Pak
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Seohyeon An
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
- Department of Physics, Hanyang University, Seoul, Republic of Korea
| | - Wonjoong Cheon
- Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Dongho Shin
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Young Kyung Lim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Jong Hwi Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Haksoo Kim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Yoonsun Chung
- Department of Nuclear Engineering, Hanyang University, Seoul, Republic of Korea
| | - Sang Hyoun Choi
- Radiation Therapy Technology and Standards, Korea Institute of Radiological & Medical Sciences, Seoul, Republic of Korea
| | - Se Byeong Lee
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
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Hoegele W, Zhang V, Grace Vasquez E, Gineitaite I, Sajo E, Brivio D, Zygmanski P. Radioactive source localization employing resistive electrode array (REA) detector. Biomed Phys Eng Express 2024; 10:025027. [PMID: 38306969 DOI: 10.1088/2057-1976/ad25bd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 02/02/2024] [Indexed: 02/04/2024]
Abstract
Objective.In this feasibility study, we explore an application of a Resistive Electrode Array (REA) for localization of a radioactive point source. The inverse problem posed by multichannel REA detection is studied from mathematical perspective and involves the questions of the minimal configuration of the conductive leads that can achieve this goal. The basic configuration consists of a circularly shaped REA with four opposite electrical lead-pairs at its perimeter.Approach.A robust mathematical reconstruction method for a 3D radioactive source relative to the REA is presented. The characteristic empirical Green's function for the detector response of the REA is determined by numerically solving Laplace equations with appropriate boundary conditions. Based on this model, Monte Carlo simulations of the inverse problem with Gaussian noise are performed and the overall accuracy of the localization is investigated.Main results.The results show a 3D error distribution of localization which is uniform in the (x,y)-plane of the REA and strongly correlated in the orthogonalz-axis. The overall accuracy decreases with higher distance of the source to the detector which is intuitive due to approximate flux dependence following the inverse square law. Further, a saturation in accuracy regarding the number of electrical leads and a linear dependence of the reconstruction error on the measurement noise level are observed.Significance.A broad range of REA detector configurations and their characteristics are investigated by this study for radioactive source localization allowing diverse practical applications with detector diameters ranging from millimeters to meters.
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Affiliation(s)
- Wolfgang Hoegele
- Munich University of Applied Sciences HM, Department of Computer Science and Mathematics, Germany
| | - Victoria Zhang
- Department of Physics, Harvard University, Cambridge, MA, 02138, United States of America
| | - Elena Grace Vasquez
- Department of Physics, University of California, Berkeley, CA, 94720-7300, United States of America
| | - Indre Gineitaite
- Department of Radiation Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, United States of America
| | - Erno Sajo
- Department of Physics and Applied Physics, Medical Physics Program, University of Massachusetts Lowell, Lowell, MA, 01854, United States of America
| | - Davide Brivio
- Department of Radiation Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, United States of America
| | - Piotr Zygmanski
- Department of Radiation Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, United States of America
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Jeong S, Kim C, An S, Kwon YC, Pak SI, Cheon W, Shin D, Lim Y, Jeong JH, Kim H, Lee SB. Determination of the proton LET using thin film solar cells coated with scintillating powder. Med Phys 2023; 50:1194-1204. [PMID: 36135795 DOI: 10.1002/mp.15977] [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: 03/04/2022] [Revised: 08/30/2022] [Accepted: 08/30/2022] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The amount of luminescent light detected in a scintillator is reduced with increased proton linear energy transfer (LET) despite receiving the same proton dose, through a phenomenon called quenching. This study evaluated the ability of a solar cell coated with scintillating powder (SC-SP) to measure therapeutic proton LET by measuring the quenching effect of the scintillating powder using a solar cell while simultaneously measuring the dose of the proton beam. METHODS SC-SP was composed of a flexible thin film solar cell and scintillating powder. The LET and dose of the pristine Bragg peak in the 14 cm range were calculated using a validated Monte Carlo model of a double scattering proton beam nozzle. The SC-SP was evaluated by measuring the proton beam under the same conditions at specific depths using SC-SP and Markus chamber. Finally, the 10 and 20 cm range pristine Bragg peaks and 5 cm spread-out Bragg peak (SOBP) in the 14 cm range were measured using the SC-SP and the Markus chamber. LETs measured using the SC-SP were compared with those calculated using Monte Carlo simulations. RESULTS The quenching factors of the SC-SP and solar cell alone, which were slopes of linear fit obtained from quenching correction factors according to LET, were 0.027 and 0.070 µm/keV (R2 : 0.974 and 0.975). For pristine Bragg peaks in the 10 and 20 cm ranges, the maximum differences between LETs measured using the SC-SP and calculated using Monte Carlo simulations were 0.5 keV/µm (15.7%) and 1.2 keV/µm (12.0%), respectively. For a 5 cm SOBP proton beam, the LET measured using the SC-SP and calculated using Monte Carlo simulations differed by up to 1.9 keV/µm (18.7%). CONCLUSIONS Comparisons of LETs for pristine Bragg peaks and SOBP between measured using the SC-SP and calculated using Monte Carlo simulations indicated that the solar cell-based system could simultaneously measure both LET and dose in real-time and is cost-effective.
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Affiliation(s)
- Seonghoon Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Chankyu Kim
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Seohyeon An
- Proton Therapy Center, National Cancer Center, Goyang, Korea.,Department of Physics, Hanyang University, Seoul, Korea
| | - Yong-Cheol Kwon
- Department of Radiation Oncology, Samsung Medical Center, Seoul, Korea
| | - Sang-Il Pak
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Wonjoong Cheon
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Dongho Shin
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Youngkyung Lim
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Jong Hwi Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Haksoo Kim
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Se Byeong Lee
- Proton Therapy Center, National Cancer Center, Goyang, Korea
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Jeong S, An S, Kwon YC, Pak SI, Cheon W, Shin D, Lim YK, Jeong JH, Kim H, Lee SB. Development of a real-time in vivo dosimetry tool for electron beam therapy using a flexible thin film solar cell coated with scintillator powder. Med Phys 2023; 50:557-569. [PMID: 35993665 DOI: 10.1002/mp.15947] [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: 05/03/2022] [Revised: 08/12/2022] [Accepted: 08/15/2022] [Indexed: 01/25/2023] Open
Abstract
PURPOSE A real-time solar cell based in vivo dosimetry system (SC-IVD) was developed using a flexible thin film solar cell and scintillating powder. The present study evaluated the clinical feasibility of the SC-IVD in electron beam therapy. METHODS A thin film solar cell was coated with 100 mg of scintillating powder using an optical adhesive to enhance the sensitivity of the SC-IVD. Calibration factors were obtained by dividing the dose, measured at a reference depth for 6-20 MeV electron beam energy, by the signal obtained using the SC-IVD. Dosimetric characteristics of SC-IVDs containing variable quantities of scintillating powder (0-500 mg) were evaluated, including energy, dose rate, and beam angle dependencies, as well as dose linearity. To determine the extent to which the SC-IVD affected the dose to the medium, doses at R90 were compared depending on whether the SC-IVD was on the surface. Finally, the accuracy of surface doses measured using the SC-IVD was evaluated by comparison with surface doses measured using a Markus chamber. RESULTS Charge measured using the SC-IVD increased linearly with dose and was within 1% of the average signal according to the dose rate. The signal generated by the SC-IVD increased as the beam angle increased. The presence of the SC-IVD on the surface of a phantom resulted in a 0.5%-2.2% reduction in dose at R90 for 6-20 MeV electron beams compared with the bare phantom. Surface doses measured using the SC-IVD system and Markus chamber differed by less than 5%. CONCLUSIONS The dosimetric characteristics of the SC-IVD were evaluated in this study. The results showed that it accurately measured the surface dose without a significant difference of dose in the medium when compared with the Markus chamber. The flexibility of the SC-IVD allows it to be attached to a patient's skin, enabling real-time and cost-effective measurement.
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Affiliation(s)
- Seonghoon Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Seohyeon An
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea.,Department of Physics, Hanyang University, Seoul, Republic of Korea
| | - Yong-Cheol Kwon
- Department of Radiation Oncology, Samsung Medical Center, Seoul, Republic of Korea
| | - Sang-Il Pak
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Wonjoong Cheon
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Dongho Shin
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Young Kyung Lim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Jong Hwi Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Haksoo Kim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Se Byeong Lee
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
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Shin DS, Kim TH, Rah JE, Lee SB, Lim YK, Jeong J, Kim H, Shin D, Son J. Flexible real-time skin dosimeter based on a thin-film copper indium gallium selenide solar cell for electron radiation therapy. Med Phys 2022; 50:2402-2416. [PMID: 36583513 DOI: 10.1002/mp.16191] [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: 04/20/2022] [Revised: 11/20/2022] [Accepted: 12/13/2022] [Indexed: 12/31/2022] Open
Abstract
PURPOSE Various dosimeters have been proposed for skin dosimetry in electron radiotherapy. However, one main drawback of these skin dosimeters is their lack of flexibility, which could make accurate dose measurements challenging due to air gaps between a curved patient surface and dosimeter. Therefore, the purpose of this study is to suggest a novel flexible skin dosimeter based on a thin-film copper indium gallium selenide (CIGS) solar cell, and to evaluate its dosimetric characteristics. METHODS The CIGS solar cell dosimeter consisted of (a) a customized thin-film CIGS solar cell and (b) a data acquisition (DAQ) system. The CIGS solar cell with a thickness of 0.33 mm was customized to a size of 10 × 10 mm2 . This customized solar cell plays a role in converting therapeutic electron radiation into electrical signals. The DAQ system was composed of a voltage amplifier with a gain of 1000, a voltage input module, a DAQ chassis, and an in-house software. This system converted the electrical analog signals (from solar cell) to digital signals with a sampling rate of ≤50 kHz and then quantified/visualized the digital signals in real time. We quantified the linearity/ sampling rate effect/dose rate dependence/energy dependence/field size output factor/reproducibility/curvature/bending recoverability/angular dependence of the CIGS solar cell dosimeter in therapeutic electron beams. To evaluate clinical feasibility, we measured the skin point doses by attaching the CIGS solar cell to an anthropomorphic phantom surface (for forehead, mouth, and thorax). The CIGS-measured doses were compared with calculated doses (by treatment planning system) and measured doses (by optically stimulated luminescent dosimeter). RESULTS The normalized signals of the solar cell dosimeter increased linearly as the delivered dose increased. The gradient of the linearly fitted line was 1.00 with an R-square of 0.9999. The sampling rates (2, 10, and 50 kHz) of the solar cell dosimeter showed good performance even at low doses (<50 cGy). The solar cell dosimeter exhibited dose rate independence within 1% and energy independence within 3% error margins. The signals of the solar cell dosimeter were similar (<1%) when penetrating the same side of the CIGS cell regardless of the rotation angle of the solar cell. The field size output factor measured by the solar cell dosimeter was comparable to that measured by the ion chamber. The solar cell signals were similar between the baseline (week 1) and the last time point (week 4). Our detector showed curvature independence within 1.8% (curvatures of <0.10 mm- ) and bending recovery (curvature of 0.10 mm-1 ). The differences between measured doses (CIGS solar cell dosimeter vs. optically stimulated luminescent dosimeter) were 7.1%, 9.6%, and 1.0% for forehead, mouth, and thorax, respectively. CONCLUSION We present the construction of a flexible skin dosimeter based on a CIGS solar cell. Our findings demonstrate that the CIGS solar cell has a potential to be a novel flexible skin dosimeter for electron radiotherapy. Moreover, this dosimeter is manufactured with low cost and can be easily customized to various size/shape, which represents advantages over other dosimeters.
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Affiliation(s)
- Dong-Seok Shin
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Tae-Ho Kim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Jeong-Eun Rah
- Department of Radiation Oncology, Myongji Hospital, Goyang, Republic of Korea
| | - Se Byeong Lee
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Young Kyung Lim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Jonghwi Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Haksoo Kim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Dongho Shin
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Jaeman Son
- Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea
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Shin DS, Kim TH, Rah JE, Kim D, Yang HJ, Lee SB, Lim YK, Jeong J, Kim H, Shin D, Son J. Assessment of a Therapeutic X-ray Radiation Dose Measurement System Based on a Flexible Copper Indium Gallium Selenide Solar Cell. SENSORS (BASEL, SWITZERLAND) 2022; 22:5819. [PMID: 35957376 PMCID: PMC9370937 DOI: 10.3390/s22155819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Revised: 08/02/2022] [Accepted: 08/02/2022] [Indexed: 06/15/2023]
Abstract
Several detectors have been developed to measure radiation doses during radiotherapy. However, most detectors are not flexible. Consequently, the airgaps between the patient surface and detector could reduce the measurement accuracy. Thus, this study proposes a dose measurement system based on a flexible copper indium gallium selenide (CIGS) solar cell. Our system comprises a customized CIGS solar cell (with a size 10 × 10 cm2 and thickness 0.33 mm), voltage amplifier, data acquisition module, and laptop with in-house software. In the study, the dosimetric characteristics, such as dose linearity, dose rate independence, energy independence, and field size output, of the dose measurement system in therapeutic X-ray radiation were quantified. For dose linearity, the slope of the linear fitted curve and the R-square value were 1.00 and 0.9999, respectively. The differences in the measured signals according to changes in the dose rates and photon energies were <2% and <3%, respectively. The field size output measured using our system exhibited a substantial increase as the field size increased, contrary to that measured using the ion chamber/film. Our findings demonstrate that our system has good dosimetric characteristics as a flexible in vivo dosimeter. Furthermore, the size and shape of the solar cell can be easily customized, which is an advantage over other flexible dosimeters based on an a-Si solar cell.
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Affiliation(s)
- Dong-Seok Shin
- Proton Therapy Center, National Cancer Center, Goyang 10408, Korea
| | - Tae-Ho Kim
- Proton Therapy Center, National Cancer Center, Goyang 10408, Korea
| | - Jeong-Eun Rah
- Department of Radiation Oncology, Myongji Hospital, Goyang 10475, Korea
| | - Dohyeon Kim
- Proton Therapy Center, National Cancer Center, Goyang 10408, Korea
| | - Hye Jeong Yang
- Proton Therapy Center, National Cancer Center, Goyang 10408, Korea
| | - Se Byeong Lee
- Proton Therapy Center, National Cancer Center, Goyang 10408, Korea
| | - Young Kyung Lim
- Proton Therapy Center, National Cancer Center, Goyang 10408, Korea
| | - Jonghwi Jeong
- Proton Therapy Center, National Cancer Center, Goyang 10408, Korea
| | - Haksoo Kim
- Proton Therapy Center, National Cancer Center, Goyang 10408, Korea
| | - Dongho Shin
- Proton Therapy Center, National Cancer Center, Goyang 10408, Korea
| | - Jaeman Son
- Department of Radiation Oncology, Seoul National University Hospital, Seoul 03080, Korea
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Jeong S, Cheon W, Shin D, Lim YK, Jeong J, Kim H, Yoon M, Lee SB. Development of a dosimetry system for therapeutic X-rays using a flexible amorphous silicon thin-film solar cell with a scintillator screen. Med Phys 2022; 49:4768-4779. [PMID: 35396722 DOI: 10.1002/mp.15664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 04/01/2022] [Accepted: 04/03/2022] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To evaluate the dosimetric characteristics and applications of a dosimetry system composed of a flexible amorphous silicon thin-film solar cell and scintillator screen (STFSC-SS) for therapeutic X-rays. METHODS The real-time dosimetry system was composed of a flexible a-Si thin film solar cell (0.2-mm thick), a scintillator screen to increase its efficiency, and an electrometer to measure the generated charge. The dosimetric characteristics of the developed system were evaluated, including its energy dependence, dose linearity, and angular dependence. Calibration factors for the signal measured by the system and absorbed dose-to-water were obtained by setting reference conditions. The application and correction accuracy of the developed system were evaluated by comparing the absorbed dose-to-water measured using a patient treatment beam with that measured using the ion chamber. RESULTS The responses of STFSC-SS to energy, field size, depth, and source-to-surface distance (SSD) were more dependent on measurement conditions than were the responses of the ion chamber, although the former dependence was due to the scintillator screen, not the solar cell. The signal of STFSC-SS were also dependent on dose rate, while the responses of solar cell alone and scintillator screen were not dependent on dose rate. The scintillator screen reduced the output of solar cell 6 and 15 MV by 0.60% and 0.55%, respectively. The absorbed doses-to-water measured using STFSC-SS for patient treatment beam differed by 0.4% compared to those measured using the ionization chamber. The uncertainties of the developed system for 6 and 15 MV photon beams were 1.8% and 1.7%, respectively, confirming the accuracy and applicability of this system. CONCLUSIONS ; The thin film solar cell-based detector developed in this study can accurately measure absorbed dose-to-water. The increased signal resulting from the use of the scintillator screen is advantageous for measuring low doses and stable signal output. In addition, this system is flexible, making it applicable to curved surfaces such as a patient's body, and is cost-effective. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Seonghoon Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Wonjoong Cheon
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Dongho Shin
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Young Kyung Lim
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Jonghwi Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Haksoo Kim
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Myonggeun Yoon
- Department of Bio-convergence Engineering, Korea University, Seoul, Korea
| | - Se Byeong Lee
- Proton Therapy Center, National Cancer Center, Goyang, Korea
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Dudas D, Semmler M, Průša P, Neue G, Koniarova I, Peterkova K, Gallus P, Koncek O, Vrba V. The use of Pantherpix pixel detector in radiotherapy QA. Phys Med 2021; 82:332-340. [PMID: 33721792 DOI: 10.1016/j.ejmp.2021.01.072] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 12/23/2020] [Accepted: 01/16/2021] [Indexed: 11/17/2022] Open
Abstract
There are various different detectors, which can be used for radiotherapy measurements, and more are about to be adopted. Hybrid pixel detectors (HPD) have been originally developed for the high energy physics. However, over the last few years they also expanded in the medical physics. Novel 2D detector Pantherpix is a HPD designed specifically for the radiotherapy. In this article, its properties are characterised and an assessment of its use in radiotherapy photon beams is provided. Properties such as response stability, response linearity, angular dependence and energy dependence were studied. In order to prove sufficient clinical quality for relative dosimetry, further measurements were undertaken (i.e. dose profiles and collimator scatter factors). Acquired results were compared with ion chamber and gafchromic film results. Namely the applicability of PhPix for cobalt beam therapy, which is still widely used (and will be used in near future) in economically less developed countries, is considered.
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Affiliation(s)
- Denis Dudas
- CTU - Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic; UJP PRAHA a.s., Prague, Czech Republic.
| | | | - Petr Průša
- CTU - Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
| | - Gordon Neue
- CTU - Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic
| | - Irena Koniarova
- National Radiation Protection Institute v.v.i., Prague, Czech Republic
| | | | | | | | - Vaclav Vrba
- CTU - Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic
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Temiño I, Basiricò L, Fratelli I, Tamayo A, Ciavatti A, Mas-Torrent M, Fraboni B. Morphology and mobility as tools to control and unprecedentedly enhance X-ray sensitivity in organic thin-films. Nat Commun 2020; 11:2136. [PMID: 32358502 PMCID: PMC7195493 DOI: 10.1038/s41467-020-15974-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 03/27/2020] [Indexed: 12/14/2022] Open
Abstract
Organic semiconductor materials exhibit a great potential for the realization of large-area solution-processed devices able to directly detect high-energy radiation. However, only few works investigated on the mechanism of ionizing radiation detection in this class of materials, so far. In this work we investigate the physical processes behind X-ray photoconversion employing bis-(triisopropylsilylethynyl)-pentacene thin-films deposited by bar-assisted meniscus shearing. The thin film coating speed and the use of bis-(triisopropylsilylethynyl)-pentacene:polystyrene blends are explored as tools to control and enhance the detection capability of the devices, by tuning the thin-film morphology and the carrier mobility. The so-obtained detectors reach a record sensitivity of 1.3 · 104 µC/Gy·cm2, the highest value reported for organic-based direct X-ray detectors and a very low minimum detectable dose rate of 35 µGy/s. Thus, the employment of organic large-area direct detectors for X-ray radiation in real-life applications can be foreseen. Though organic semiconductors are attractive for high performance X-ray detection systems, the detection mechanism in organic thin films is not well understood. Here, the authors report the role of morphology and carrier mobility on X-ray sensitivity in detectors with unprecedented performance.
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Affiliation(s)
- Inés Temiño
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193, Bellaterra, Spain.,CIBER-BBN, Campus de la UAB, 08193, Bellaterra, Spain
| | - Laura Basiricò
- Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127, Bologna, Italy.,National Institute for Nuclear Physics-INFN section of Bologna, Bologna, Italy
| | - Ilaria Fratelli
- Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127, Bologna, Italy.,National Institute for Nuclear Physics-INFN section of Bologna, Bologna, Italy
| | - Adrián Tamayo
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193, Bellaterra, Spain.,CIBER-BBN, Campus de la UAB, 08193, Bellaterra, Spain
| | - Andrea Ciavatti
- Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127, Bologna, Italy.,National Institute for Nuclear Physics-INFN section of Bologna, Bologna, Italy
| | - Marta Mas-Torrent
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193, Bellaterra, Spain. .,CIBER-BBN, Campus de la UAB, 08193, Bellaterra, Spain.
| | - Beatrice Fraboni
- Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127, Bologna, Italy. .,National Institute for Nuclear Physics-INFN section of Bologna, Bologna, Italy.
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Albert S, Brivio D, Aldelaijan S, Sajo E, Hesser J, Zygmanski P. Towards customizable thin-panel low-Z detector arrays: electrode design for increased spatial resolution ion chamber arrays. Phys Med Biol 2020; 65:08NT02. [PMID: 32187595 DOI: 10.1088/1361-6560/ab8109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of the present development is to employ 3D printing to prototype an ion chamber array with a scalable design potentially allowing increased spatial resolution and a larger active area. An additional goal is to design and fabricate a custom size thin-panel detector array with low-Z components. As a proof of principle demonstration, a medium size detector array with 30 × 30 air-vented ion chambers was 3D-printed using PLA as frame for the electrodes. The active-area is 122 mm × 120 mm with 4 × 4 mm2 spatial resolution. External electrodes are cylindrical and made from conductive PLA. Internal electrodes are made from microwire. The array is symmetric with respect to the central plane and its thickness is 10 mm including build-up/-down plates of 2.5 mm thickness. Data acquisition is realized by biasing only selected chamber rows and reading only 30 chambers at a time. To test the device for potential clinical applications, 1D dose profiles and 2D dose maps with various square and irregular fields were measured. The overall agreement with the reference doses (film and treatment planning system) was satisfactory, but the measured dose differs in the penumbra region and in the field size dependence. Both of these features are related to the thin walls between neighboring ion chambers and different lateral phantom scatter in the detector panel vs homogeneous material. We demonstrated feasibility of radiation detector arrays with minimal number of readout channels and low-cost electronics. The acquisition scheme based on selected row or column 'activation' by bias voltage is not practical for 2D dosimetry but it allows for rapid turn-around when testing of custom arrays with the aid of multiple 1D dose profiles. Future progress in this area includes overcoming the limitations due high chamber packing ratio, which leads to the lateral scattering effects.
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Affiliation(s)
- Steffen Albert
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States of America. Heidelberg University, Heidelberg, Germany. University of Massachusetts Lowell, MA, United States of America
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11
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Amplification of Radiation-Induced Signal of LED Strip by Increasing Number of LED Chips and Using Amplifier Board. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10020651] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Transducers, such as photodiodes, phototransistors, and photovoltaic cells are promising radiation detectors. However, for accurate radiation detection and dosimetry, signals that emanate from these devices have to be sufficient to facilitate accurate calibrations, i.e., assigning a quantity of radiation dose to a specific magnitude of the signal. More so, purposely fabricated for luminescence, LEDs produce significantly low signals during radiation detection applications. Therefore, this paper investigates the enhancement and augmentation of photovoltaic signals that were generated when LED strips were being exposed to diagnostic X-rays. Initially, signal amplification was achieved through increasing the effective LED active area (from 60 to 120 chips); by successively connecting LED strips. Further, signal amplification was undertaken by injecting the raw LED strip signal into an amplifier board with adjustable gains. In both the signal amplification techniques, the tube voltage (kVp), tube current-time product (mAs), and source-to-detector distance (SDD) were varied. The principal findings show that effective active area-based signal amplifications produced an overall average of 91.16% signal enhancement throughout all of the X-ray parameter variations. On the other hand, the amplifier board produced an average of 36.48% signal enhancement for the signals that were injected into it. Chip number increment-based signal amplifications had a 0.687% less coefficient of variation than amplifier board signal amplifications. The amplifier board signal amplifications were impaired by factors, such as dark currents, amplifier board maximum operational output voltage, and saturation. Therefore, future electronic signal amplification could use amplifier boards having low dark currents and high operational voltage headroom. The low-cost and simplicity that are associated with active-area amplification could be further exploited in a hybrid amplification technique with electronic amplification and scintillators.
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Comparison of Current–Voltage Response to Diagnostic X-rays of Five Light-Emitting Diode Strips. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app10010200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Light-emitting diodes (LEDs) have miscellaneous applications owing to their low cost, small size, flexibility, and commercial availability. Furthermore, LEDs have dual applicability as light emitters and detectors. This study explores the current–voltage (C–V) response of LED strips exposed to diagnostic x-rays. Cold white, warm white, red, green, and blue LED strip colors were tested. Each strip consisted of 12 LED chips and was connected to a multimeter. The variable diagnostic x-ray parameters evaluated were kilovoltage peak (kVp), milliampere-seconds (mAs), and source-to-image distance (SID). The radiation dose was also measured using a dosimeter simultaneously exposed to x-rays perpendicularly incident on the strips. Lastly, the consistency of C–V responses, and any possible degradation after 1–2 months was also analyzed. Each LED strip color was ranked according to its C–V response in each of the investigated parameters. The LED strip color with the best cumulative rank across all the tested parameters was then examined for reproducibility. Our findings revealed that the C–V responses of LED strips are (a) generally low but measurable, (b) inconsistent and fluctuating as a consequence of kVp variations, (c) positively correlated to mAs, (d) negatively correlated to SID, and (e) positively correlated to dose. Overall results suggested cold white LED strip as most feasible for x-ray detection—in comparison to examined colors. Additionally, the reproducibility study using the cold white LED strip found a similar trend of C–V response to all variables except kVp. Outcomes indicate that LED strips have the potential to be exploited for detecting low dose (~0–100 mGy) diagnostic x-rays. However, future studies should be carried out to increase the low C–V signal.
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Pushpavanam K, Inamdar S, Dutta S, Bista T, Sokolowski T, Boshoven E, Sapareto S, Rege K. Determination of topographical radiation dose profiles using gel nanosensors. SCIENCE ADVANCES 2019; 5:eaaw8704. [PMID: 31763446 PMCID: PMC6858262 DOI: 10.1126/sciadv.aaw8704] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 09/20/2019] [Indexed: 06/10/2023]
Abstract
Despite the emergence of sophisticated technologies in treatment planning and administration, routine determination of delivered radiation doses remains a challenge due to limitations associated with conventional dosimeters. Here, we describe a gel-based nanosensor for the colorimetric detection and quantification of topographical radiation dose profiles in radiotherapy. Exposure to ionizing radiation results in the conversion of gold ions in the gel to gold nanoparticles, which render a visual change in color in the gel due to their plasmonic properties. The intensity of color formed in the gel was used as a quantitative reporter of ionizing radiation. The gel nanosensor was used to detect complex topographical dose patterns including those administered to an anthropomorphic phantom and live canine patients undergoing clinical radiotherapy. The ease of fabrication, operation, rapid readout, colorimetric detection, and relatively low cost illustrate the translational potential of this technology for topographical dose mapping in radiotherapy applications in the clinic.
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Affiliation(s)
- Karthik Pushpavanam
- Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287, USA
| | - Sahil Inamdar
- Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287, USA
| | - Subhadeep Dutta
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Tomasz Bista
- Banner MD Anderson Cancer Center, Gilbert, AZ 85234, USA
| | | | | | | | - Kaushal Rege
- Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287, USA
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Cho S, Ahn SH, Cho IJ, Kim YH, Jeong JU, Yoon MS, Ahn SJ, Chung WK, Nam TK, Song JY. Radiation hardness of cadmium telluride solar cells in proton therapy beam mode. PLoS One 2019; 14:e0221655. [PMID: 31513591 PMCID: PMC6742456 DOI: 10.1371/journal.pone.0221655] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Accepted: 08/12/2019] [Indexed: 11/18/2022] Open
Abstract
We evaluated the durability of cadmium telluride (CdTe) solar cells upon proton beam irradiation as well as the possibility of achieving a dosimeter usable in proton beam therapy by applying 100 MeV of pencil beam scanning (PBS) irradiation. Specifically, a 100 MeV proton PBS beam was applied at irradiation doses of 0, 1012, 1013, 1014, and 1015 cm-2. According to the results, the remaining factors (defined as the ratio of the degraded value to the initial value) of open-circuit voltage (Voc), short-circuit current (Jsc), fill-factor (FF), and efficiency (ƞ) which are solar cell performance parameters, were approximately 89%, 44%, 69%, and 30%, respectively, compared to those of the reference cell (without irradiation) at the highest dose of 1×1015 cm-2. In particular, the conversion efficiency, which is the main factor, was approximately 70% of that of the reference cell even at a high fluence of 1×1014 cm-2. In addition, we observed the projected range of the hydrogen atoms based on the PBS beam energy using the Tool for Particle Simulation software and assessed the amount of fluence accumulated in a CdTe cell. As the energy increased, the fluence accumulated inside the cell tended to decrease owing to the characteristics of the Bragg peak of the proton. Thus, the radiation damage to the cell induced by the proton beam was reduced. The results of this study are expected to provide valuable reference information for research on dosimetry sensors composed of thin-film solar cells, serving as the basis for future application in proton beam therapy with CdTe solar cells.
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Affiliation(s)
- Shinhaeng Cho
- Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea
| | - Sang Hee Ahn
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Ick Joon Cho
- Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea
| | - Yong Hyub Kim
- Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea
| | - Jae-Uk Jeong
- Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea
| | - Mee Sun Yoon
- Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea
| | - Sung-Ja Ahn
- Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea
| | - Woong-Ki Chung
- Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea
| | - Taek-Keun Nam
- Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea
| | - Ju-Young Song
- Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea
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Damulira E, Yusoff MNS, Omar AF, Mohd Taib NH. A Review: Photonic Devices Used for Dosimetry in Medical Radiation. SENSORS 2019; 19:s19102226. [PMID: 31091779 PMCID: PMC6567371 DOI: 10.3390/s19102226] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Revised: 05/08/2019] [Accepted: 05/09/2019] [Indexed: 11/28/2022]
Abstract
Numerous instruments such as ionization chambers, hand-held and pocket dosimeters of various types, film badges, thermoluminescent dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs) are used to measure and monitor radiation in medical applications. Of recent, photonic devices have also been adopted. This article evaluates recent research and advancements in the applications of photonic devices in medical radiation detection primarily focusing on four types; photodiodes – including light-emitting diodes (LEDs), phototransistors—including metal oxide semiconductor field effect transistors (MOSFETs), photovoltaic sensors/solar cells, and charge coupled devices/charge metal oxide semiconductors (CCD/CMOS) cameras. A comprehensive analysis of the operating principles and recent technologies of these devices is performed. Further, critical evaluation and comparison of their benefits and limitations as dosimeters is done based on the available studies. Common factors barring photonic devices from being used as radiation detectors are also discussed; with suggestions on possible solutions to overcome these barriers. Finally, the potentials of these devices and the challenges of realizing their applications as quintessential dosimeters are highlighted for future research and improvements.
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Affiliation(s)
- Edrine Damulira
- Medical Radiation Programme, School of Health Sciences, Universiti Sains Malaysia, Kubang Kerian 16150, Malaysia.
| | - Muhammad Nur Salihin Yusoff
- Medical Radiation Programme, School of Health Sciences, Universiti Sains Malaysia, Kubang Kerian 16150, Malaysia.
| | - Ahmad Fairuz Omar
- Engineering Physics Laboratory, School of Physics, Universiti Sains Malaysia, Penang 11800, Malaysia.
| | - Nur Hartini Mohd Taib
- Department of Radiology, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian 16150, Malaysia.
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Brivio D, Ada E, Sajo E, Zygmanski P. Effective Contact Potential of Thin Film Metal-Insulator Nanostructures and Its Role in Self-Powered Nanofilm X-ray Sensors. ACS APPLIED MATERIALS & INTERFACES 2017; 9:11258-11265. [PMID: 28269982 DOI: 10.1021/acsami.7b01264] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We studied the effective contact potential difference (ECPD) of thin film nanostructures and its role in self-powered X-ray sensors, which use the high-energy current detection scheme. We compared the response to kilovoltage X-rays of several nanostructures made of disparate combinations of conductors (Al, Cu, Ta, ITO) and oxides (SiO2, Ta2O5, Al2O3). We measured current-voltage curves in parallel-plate configuration separated by an air gap and determined three characteristic parameters: current at zero voltage bias I0, the voltage offset for zero current ECPD, and saturation current Isat. We found that the metals' ECPD values measured with our technique were higher than the CPD values measured with photoelectron spectroscopy in situ, i.e., no air contact. These differences are related to natural oxidization and to the presence of photo-/Auger-electron current leaking from the high-Z toward the low-Z electrode, as suggested by additional experiments carried out in vacuum. Further, the deposition of the 40-500 nm oxide layer on the surface of metallic substrates strongly affects their contact potential. This technique exploits ionization and charge carrier transport in both solid insulators and in air, and it opens the possibility of measuring the ECPD between metals separated by a solid insulator in a metal-insulator-metal (MIM) configuration. Additionally, we demonstrated that certain configurations of MIM structures are suitable for X-ray detection in self-powered mode.
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Affiliation(s)
- Davide Brivio
- Brigham & Women's Hospital , Boston, Massachusetts 02115, United States
- Dana Farber Cancer Institute, Harvard Medical School , Boston, Massachusetts 02215, United States
| | - Earl Ada
- University of Massachusetts Lowell , Lowell, Massachusetts 01854, United States
| | - Erno Sajo
- University of Massachusetts Lowell , Lowell, Massachusetts 01854, United States
| | - Piotr Zygmanski
- Brigham & Women's Hospital , Boston, Massachusetts 02115, United States
- Dana Farber Cancer Institute, Harvard Medical School , Boston, Massachusetts 02215, United States
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Brivio D, Sajo E, Zygmanski P. Technical Note: A novel interdigital transparent thin-film detector for medical dosimetry. Med Phys 2017; 44:1969-1974. [PMID: 28122117 DOI: 10.1002/mp.12129] [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: 07/18/2016] [Revised: 01/12/2017] [Accepted: 01/15/2017] [Indexed: 11/10/2022] Open
Abstract
PURPOSE A new type of thin-film interdigital detector (TFID) for medical dosimetry is investigated. The focus of this study was to characterize the detector response as a function of detector geometry in an attempt to optimize it and to understand the underlying radio-electrical effects leading to signal formation. METHODS We characterize the detector response to kilovoltage x-ray beams used in fluoroscopy and computed tomography. Each element (pixel) of the detector is composed of conductive intercombing digits deposited on a thin-film dielectric substrate by nanofabrication or using a printing process. The detector is practically transparent to x-ray radiation, yet it generates sufficient signal for many types of medical dosimetry and quality assurance tasks. The thin-film detector has negligible surface mass density (about 2.5 mg/cm2 for a 1-μm-thick Cu TFID on 12.5-μm-thick Kapton substrate) and it is conformable to curved geometries found in the medical x-ray equipment or on patient skin surface. The prototype detectors were made using glass and Kapton substrates with copper-copper and copper-aluminum interdigits. Although in principle the detector can be operated without any external bias voltage when the digits are made of disparate materials (e.g., Cu-Al), we also characterized the detector properties under small electric fields via its current-voltage curve (IV curve). RESULTS Using 120 kVp, 25 mA x-ray beam with 10V external bias, the Cu-Cu detector response was about 0.2 nA/cm2 . We also measured a one-dimensional transmitted dose profile for a phantom under fluoroscopic x-rays and found relatively good agreement with a commercial photodiode (XR R12-0191, IBA Dosimetry). CONCLUSIONS We demonstrated the potential of TFID detectors for kilovoltage dosimetry and we defined its optimal geometry. For digits made of the same material and for digit width equal to the separation between them, we found that the thin-film detector has optimal performance when the distance between the digit centers is about 1 mm, while in the fixed digit width cases we observed that the signal is higher when their edge-to-edge separation is as small as possible.
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Affiliation(s)
- Davide Brivio
- Brigham & Woman's Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, 02115, USA
| | - Erno Sajo
- University of Massachusetts, Lowell, MA, 01854, USA
| | - Piotr Zygmanski
- Brigham & Woman's Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, 02115, USA
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Basiricò L, Ciavatti A, Cramer T, Cosseddu P, Bonfiglio A, Fraboni B. Direct X-ray photoconversion in flexible organic thin film devices operated below 1 V. Nat Commun 2016; 7:13063. [PMID: 27708274 PMCID: PMC5059709 DOI: 10.1038/ncomms13063] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 09/01/2016] [Indexed: 11/25/2022] Open
Abstract
The application of organic electronic materials for the detection of ionizing radiations is very appealing thanks to their mechanical flexibility, low-cost and simple processing in comparison to their inorganic counterpart. In this work we investigate the direct X-ray photoconversion process in organic thin film photoconductors. The devices are realized by drop casting solution-processed bis-(triisopropylsilylethynyl)pentacene (TIPS-pentacene) onto flexible plastic substrates patterned with metal electrodes; they exhibit a strong sensitivity to X-rays despite the low X-ray photon absorption typical of low-Z organic materials. We propose a model, based on the accumulation of photogenerated charges and photoconductive gain, able to describe the magnitude as well as the dynamics of the X-ray-induced photocurrent. This finding allows us to fabricate and test a flexible 2 × 2 pixelated X-ray detector operating at 0.2 V, with gain and sensitivity up to 4.7 × 104 and 77,000 nC mGy−1 cm−3, respectively. Organic electronics show advantages in easy processing, mechanical flexibility and low costs compared to their inorganic counterparts, yet there are not many proofs for the sake of X-ray detection. Here, Basiricò et al. build a flexible X-ray detector operated at sub-1 V using pentacene-based thin films.
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Affiliation(s)
- Laura Basiricò
- Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, Bologna 40127, Italy
| | - Andrea Ciavatti
- Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, Bologna 40127, Italy
| | - Tobias Cramer
- Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, Bologna 40127, Italy
| | - Piero Cosseddu
- Department of Electrical and Electronic Engineering, University of Cagliari, Piazza D'Armi, Cagliari 09123, Italy
| | - Annalisa Bonfiglio
- Department of Electrical and Electronic Engineering, University of Cagliari, Piazza D'Armi, Cagliari 09123, Italy
| | - Beatrice Fraboni
- Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, Bologna 40127, Italy
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Zygmanski P, Shrestha S, Briovio D, Karellas A, Sajo E. Prototypes of self-powered radiation detectors employing intrinsic high-energy current. Med Phys 2015; 43:16. [DOI: 10.1118/1.4935532] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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20
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Zygmanski P, Sajo E. A self-powered thin-film radiation detector using intrinsic high-energy current. Med Phys 2015; 43:4. [DOI: 10.1118/1.4935531] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Elshahat B, Gill HS, Filipyev I, Shrestha S, Hesser J, Kumar J, Karellas A, Zygmanski P, Sajo E. Technical Note: Nanometric organic photovoltaic thin film detectors for dose monitoring in diagnostic x-ray imaging. Med Phys 2015; 42:4027-32. [PMID: 26133603 DOI: 10.1118/1.4922202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To fabricate organic photovoltaic (OPV) cells with nanometric active layers sensitive to ionizing radiation and measure their dosimetric characteristics in clinical x-ray beams in the diagnostic tube potential range of 60-150 kVp. METHODS Experiments were designed to optimize the detector's x-ray response and find the best parameter combination by changing the active layer thickness and the area of the electrode. The OPV cell consisted of poly (3-hexylthiophene-2,5-diyl): [6,6]-phenyl C61 butyric acid methyl ester photoactive donor and acceptor semiconducting organic materials sandwiched between an aluminum electrode as an anode and an indium tin oxide electrode as a cathode. The authors measured the radiation-induced electric current at zero bias voltage in all fabricated OPV cells. RESULTS The net OPV current as a function of beam potential (kVp) was proportional to kVp(-0.5) when normalized to x-ray tube output, which varies with kVp. Of the tested configurations, the best combination of parameters was 270 nm active layer thicknesses with 0.7 cm(2) electrode area, which provided the highest signal per electrode area. For this cell, the measured current ranged from approximately 0.7 to 2.4 nA/cm(2) for 60-150 kVp, corresponding to about 0.09 nA-0.06 nA/mGy air kerma, respectively. When compared to commercial amorphous silicon thin film photovoltaic cells irradiated under the same conditions, this represents 2.5 times greater sensitivity. An additional 40% signal enhancement was observed when a 1 mm layer of plastic scintillator was attached to the cells' beam-facing side. CONCLUSIONS Since both OPVs can be produced as flexible devices and they do not require external bias voltage, they open the possibility for use as thin film in vivo detectors for dose monitoring in diagnostic x-ray imaging.
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Affiliation(s)
- Bassem Elshahat
- Medical Physics Program, Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts 01854 and Department of Medical Imaging, Royal Jubilee Hospital, Vancouver Island Health Authority, Victoria, British Columbia V8R 1J8, Canada
| | - Hardeep Singh Gill
- Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts 01854
| | - Ilya Filipyev
- Harvard Medical School, Dana Farber Cancer Institute and Brigham and Women's Hospital, Boston, Massachusetts 02215
| | - Suman Shrestha
- Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655
| | - Jürgen Hesser
- Department of Radiation Oncology, University Medical Center Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, Mannheim 68167, Germany
| | - Jayant Kumar
- Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts 01854
| | - Andrew Karellas
- Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655
| | - Piotr Zygmanski
- Harvard Medical School, Dana Farber Cancer Institute and Brigham and Women's Hospital, Boston, Massachusetts 02215
| | - Erno Sajo
- Medical Physics Program, Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts 01854
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Zygmanski P, Shrestha S, Elshahat B, Karellas A, Sajo E. Dosimetric properties of high energy current (HEC) detector in keV x-ray beams. Phys Med Biol 2015; 60:N121-9. [PMID: 25789488 DOI: 10.1088/0031-9155/60/7/n121] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications.
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Affiliation(s)
- Piotr Zygmanski
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA 02115, USA
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