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Large MJ, Bashiri A, Dookie Y, McNamara J, Antognini L, Aziz S, Calcagnile L, Caricato AP, Catalano R, Chila D, Cirrone GAP, Croci T, Cuttone G, Dunand S, Fabi M, Frontini L, Grimani C, Ionica M, Kanxheri K, Liberali V, Maurizio M, Maruccio G, Mazza G, Menichelli M, Monteduro AG, Morozzi A, Moscatelli F, Pallotta S, Passeri D, Pedio M, Petringa G, Peverini F, Piccolo L, Placidi P, Quarta G, Rizzato S, Sabbatini F, Servoli L, Stabile A, Talamonti C, Thomet JE, Tosti L, Villani M, Wheadon RJ, Wyrsch N, Zema N, Petasecca M. Characterization of a flexible a-Si:H detector for in vivo dosimetry in therapeutic x-ray beams. Med Phys 2024; 51:4489-4503. [PMID: 38432192 DOI: 10.1002/mp.17013] [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: 10/26/2023] [Revised: 01/24/2024] [Accepted: 02/18/2024] [Indexed: 03/05/2024] Open
Abstract
BACKGROUND The increasing use of complex and high dose-rate treatments in radiation therapy necessitates advanced detectors to provide accurate dosimetry. Rather than relying on pre-treatment quality assurance (QA) measurements alone, many countries are now mandating the use of in vivo dosimetry, whereby a dosimeter is placed on the surface of the patient during treatment. Ideally, in vivo detectors should be flexible to conform to a patient's irregular surfaces. PURPOSE This study aims to characterize a novel hydrogenated amorphous silicon (a-Si:H) radiation detector for the dosimetry of therapeutic x-ray beams. The detectors are flexible as they are fabricated directly on a flexible polyimide (Kapton) substrate. METHODS The potential of this technology for application as a real-time flexible detector is investigated through a combined dosimetric and flexibility study. Measurements of fundamental dosimetric quantities were obtained including output factor (OF), dose rate dependence (DPP), energy dependence, percentage depth dose (PDD), and angular dependence. The response of the a-Si:H detectors investigated in this study are benchmarked directly against commercially available ionization chambers and solid-state diodes currently employed for QA practices. RESULTS The a-Si:H detectors exhibit remarkable dose linearities in the direct detection of kV and MV therapeutic x-rays, with calibrated sensitivities ranging from (0.580 ± 0.002) pC/cGy to (19.36 ± 0.10) pC/cGy as a function of detector thickness, area, and applied bias. Regarding dosimetry, the a-Si:H detectors accurately obtained OF measurements that parallel commercially available detector solutions. The PDD response closely matched the expected profile as predicted via Geant4 simulations, a PTW Farmer ionization chamber and a PTW ROOS chamber. The most significant variation in the PDD performance was 5.67%, observed at a depth of 3 mm for detectors operated unbiased. With an external bias, the discrepancy in PDD response from reference data was confined to ± 2.92% for all depths (surface to 250 mm) in water-equivalent plastic. Very little angular dependence is displayed between irradiations at angles of 0° and 180°, with the most significant variation being a 7.71% decrease in collected charge at a 110° relative angle of incidence. Energy dependence and dose per pulse dependence are also reported, with results in agreement with the literature. Most notably, the flexibility of a-Si:H detectors was quantified for sample bending up to a radius of curvature of 7.98 mm, where the recorded photosensitivity degraded by (-4.9 ± 0.6)% of the initial device response when flat. It is essential to mention that this small bending radius is unlikely during in vivo patient dosimetry. In a more realistic scenario, with a bending radius of 15-20 mm, the variation in detector response remained within ± 4%. After substantial bending, the detector's photosensitivity when returned to a flat condition was (99.1 ± 0.5)% of the original response. CONCLUSIONS This work successfully characterizes a flexible detector based on thin-film a-Si:H deposited on a Kapton substrate for applications in therapeutic x-ray dosimetry. The detectors exhibit dosimetric performances that parallel commercially available dosimeters, while also demonstrating excellent flexibility results.
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Affiliation(s)
- Matthew James Large
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia
| | - Aishah Bashiri
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia
- School of Physics, Najran University, Najran, Saudi Arabia
| | - Yashiv Dookie
- Shoalhaven Cancer Care Centre, Nowra, New South Wales, Australia
| | - Joanne McNamara
- Shoalhaven Cancer Care Centre, Nowra, New South Wales, Australia
| | - Luca Antognini
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab), Neuchâtel, Switzerland
| | - Saba Aziz
- INFN Sezione di Lecce, via per Arnesano, Lecce, Italy
- Department of Mathematics and Physics "Ennio de Giorgi", University of Salento, Via per Arnesano, Lecce, Italy
| | - Lucio Calcagnile
- INFN Sezione di Lecce, via per Arnesano, Lecce, Italy
- Department of Mathematics and Physics "Ennio de Giorgi", University of Salento, Via per Arnesano, Lecce, Italy
| | - Anna Paola Caricato
- INFN Sezione di Lecce, via per Arnesano, Lecce, Italy
- Department of Mathematics and Physics "Ennio de Giorgi", University of Salento, Via per Arnesano, Lecce, Italy
| | | | - Deborah Chila
- INFN Sezione di Firenze, Florence, Italy
- Department of Experimental and Biomedical Clinical Science "Mario Serio", University of Florence, Florence, Italy
| | | | | | | | - Sylvain Dunand
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab), Neuchâtel, Switzerland
| | - Michele Fabi
- INFN Sezione di Firenze, Florence, Italy
- DiSPeA, Università di Urbino Carlo Bo, Urbino, Italy
| | - Luca Frontini
- INFN Sezione di Milano, Via Celoria 16, Milan, Italy
| | - Catia Grimani
- INFN Sezione di Firenze, Florence, Italy
- DiSPeA, Università di Urbino Carlo Bo, Urbino, Italy
| | | | - Keida Kanxheri
- INFN Sezione di Perugia, Perugia, Italy
- Dip. di Fisica e Geologia dell'Università degli Studi di Perugia, Perugia, Italy
| | | | - Martino Maurizio
- INFN Sezione di Lecce, via per Arnesano, Lecce, Italy
- Department of Mathematics and Physics "Ennio de Giorgi", University of Salento, Via per Arnesano, Lecce, Italy
| | - Giuseppe Maruccio
- INFN Sezione di Lecce, via per Arnesano, Lecce, Italy
- Department of Mathematics and Physics "Ennio de Giorgi", University of Salento, Via per Arnesano, Lecce, Italy
| | | | | | - Anna Grazia Monteduro
- INFN Sezione di Lecce, via per Arnesano, Lecce, Italy
- Department of Mathematics and Physics "Ennio de Giorgi", University of Salento, Via per Arnesano, Lecce, Italy
| | | | | | - Stefania Pallotta
- INFN Sezione di Firenze, Florence, Italy
- Department of Experimental and Biomedical Clinical Science "Mario Serio", University of Florence, Florence, Italy
| | - Daniele Passeri
- INFN Sezione di Perugia, Perugia, Italy
- Dip. di Ingegneria dell'Università degli studi di Perugia, Perugia, Italy
| | - Maddalena Pedio
- INFN Sezione di Perugia, Perugia, Italy
- CNR-IOM, Perugia, Italy
| | | | - Francesca Peverini
- INFN Sezione di Perugia, Perugia, Italy
- Dip. di Fisica e Geologia dell'Università degli Studi di Perugia, Perugia, Italy
| | | | - Pisana Placidi
- INFN Sezione di Perugia, Perugia, Italy
- Dip. di Ingegneria dell'Università degli studi di Perugia, Perugia, Italy
| | - Gianluca Quarta
- INFN Sezione di Lecce, via per Arnesano, Lecce, Italy
- Department of Mathematics and Physics "Ennio de Giorgi", University of Salento, Via per Arnesano, Lecce, Italy
| | - Silvia Rizzato
- INFN Sezione di Lecce, via per Arnesano, Lecce, Italy
- Department of Mathematics and Physics "Ennio de Giorgi", University of Salento, Via per Arnesano, Lecce, Italy
| | - Federico Sabbatini
- INFN Sezione di Firenze, Florence, Italy
- DiSPeA, Università di Urbino Carlo Bo, Urbino, Italy
| | | | | | - Cinzia Talamonti
- INFN Sezione di Firenze, Florence, Italy
- Department of Experimental and Biomedical Clinical Science "Mario Serio", University of Florence, Florence, Italy
| | - Jonathan Emanuel Thomet
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab), Neuchâtel, Switzerland
| | | | - Mattia Villani
- INFN Sezione di Firenze, Florence, Italy
- DiSPeA, Università di Urbino Carlo Bo, Urbino, Italy
| | | | - Nicolas Wyrsch
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab), Neuchâtel, Switzerland
| | - Nicola Zema
- INFN Sezione di Perugia, Perugia, Italy
- CNR Istituto struttura della Materia, Rome, Italy
| | - Marco Petasecca
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia
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Li Y, Chen H, Hao Z, Wang Z, Wu X, Lu X, Li X, Zhang J. Toward Low-Voltage and High-Sensitivity Direct X-ray Detectors Based on Thick Bulk Heterojunction Organic Device. ACS APPLIED MATERIALS & INTERFACES 2024; 16:10417-10426. [PMID: 38375798 DOI: 10.1021/acsami.3c18529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
Organic semiconducting materials are promising for the fabrication of flexible ionizing radiation detectors for imaging because of their tissue equivalence, simple large-scale processing, and mass production. However, it is challenging to achieve high-sensitivity detection for organic direct detectors prepared by low-cost solution processing because of the compromise between thickness and carrier transport. In this study, high-performance organic direct X-ray detectors were fabricated by building a micrometer-thick bulk heterojunction (BHJ) using poly(3-hexylthiophene-2,5-diyl) (P3HT):(6,6)-phenyl c71 butyric acid methyl ester. A 5 μm BHJ film was fabricated by drop-casting and enhanced crystallization of P3HT using binary solvents and high-boiling-point additives to improve the charge carrier mobility. Furthermore, this organic direct X-ray detector has a sensitivity of >654.26 μC Gyair s-1 and a self-powered response. Because of the architecture of the thick active layer and the energy cascade in this diode detector, it has a very low dark current of 46.26 pA at -2 V. A fast and efficient approach was developed for fabricating thick, highly mobile organic BHJ films for high-performance direct X-ray detectors. It has great potential for application in a new generation of flexible and portable large-area flat-panel detectors.
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Affiliation(s)
- Yi Li
- School of Microelectronics, Shanghai University, Shanghai 200444, China
| | - Hu Chen
- Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai 200072, China
| | - Zhao Hao
- School of Microelectronics, Shanghai University, Shanghai 200444, China
| | - Zixuan Wang
- Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai 200072, China
| | - Xingyang Wu
- Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai 200072, China
| | - Xiuzhen Lu
- School of Microelectronics, Shanghai University, Shanghai 200444, China
| | - Xifeng Li
- Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai 200072, China
| | - Jianhua Zhang
- School of Microelectronics, Shanghai University, Shanghai 200444, China
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Kim H, Kang J, Kim MI, Jeong W, Baek S, Ahn H, Chung DS, Jung IH. Development of n-Type Small-Molecule Acceptors for Low Dark Current Density and Fast Response Organic Photodetectors. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 38032313 DOI: 10.1021/acsami.3c11174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
Suppressing the dark current density (Jd) while maintaining sufficient charge transport is important for improving the specific detectivity (D*) and dynamic characteristics of organic photodetectors (OPDs). In this study, we synthesized three novel small-molecule acceptors (SMAs) densely surrounded by insulating alkyl side chains to minimize the Jd in OPDs. Introducing trialkylated N-annulated perylene diimide as a terminal moiety to the alkylated π-conjugated core structure was highly efficient in suppressing Jd in the devices, resulting in an extremely low Jd of 4.60 × 10-11 A cm-2 and 10-100 times improved D* values in the devices. In addition, SMAs with a geometrically aligned backbone structure exhibited better intermolecular ordering in the blended films, resulting in 3-10 times as high responsivity (R) values in the OPDs. Outstanding OPD performances with a D* of 8.09 × 1012 Jones, -3 dB cutoff frequency of 205.2 kHz, and rising response time of 16 μs were achieved under a 530 nm illumination in photoconductive mode. Geometrically aligned core-terminal SMAs densely surrounded by insulating alkyl side chains are promising for improving the static and dynamic properties of OPDs.
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Affiliation(s)
- Hyeokjun Kim
- Department of Organic and Nano Engineering, and Human-Tech Convergence Program, 222 Wangsimni-ro, Seongdong-gu, Hanyang University, Seoul 04763, Republic of Korea
| | - Jinhyeon Kang
- Light/Display Convergence R&BD Division, Cheorwon Plasma Research Institute, 7194 Geumgang-ro, Seo-myeon, Cheorwon-gun, Gangwon-do 24062, Republic of Korea
| | - Myeong In Kim
- Department of Organic and Nano Engineering, and Human-Tech Convergence Program, 222 Wangsimni-ro, Seongdong-gu, Hanyang University, Seoul 04763, Republic of Korea
| | - WonJo Jeong
- Department of Organic and Nano Engineering, and Human-Tech Convergence Program, 222 Wangsimni-ro, Seongdong-gu, Hanyang University, Seoul 04763, Republic of Korea
| | - Seyeon Baek
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37363, Republic of Korea
| | - Hyungju Ahn
- Pohang Accelerator Laboratory, POSTECH, Pohang 37673, Republic of Korea
| | - Dae Sung Chung
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37363, Republic of Korea
| | - In Hwan Jung
- Department of Organic and Nano Engineering, and Human-Tech Convergence Program, 222 Wangsimni-ro, Seongdong-gu, Hanyang University, Seoul 04763, Republic of Korea
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