Chansun Park (a), Sangsu Kim (a), Hyojung Kim (b), Won-Young Jeong (b), Hochun Park (b), Jung-Yeol Yeom (c), Shinhaeng Cho (b)
(a Global Health Technology Research Center, Korea University, Seoul, 02841, Republic of Korea
(b Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
(c Department of Bioengineering, Korea University, Seoul, 02841, Republic of Korea
## Abstract
Considering the limitations of traditional semiconductors, such as Si and Ge, in high-energy radiation environments, in this study, we demonstrated the reliable and efficient performance of CdZnTe (CZT; II–IV compound semiconductor) in detecting and distinguishing radiation across a wide energy range. A 1-inch CZT crystal was grown using the vertical Bridgman method and subjected to post-processing to prepare radiation detectors. A 6 × 6 × 8 mm3 CZT sample exhibited a resistivity of 1.9 × 1010 Ω cm, which indicated reduced electrical noise and improved signal accuracy. Using a137Cs source, we achieved an energy resolution of 4.3 %, highlighting the potential of CZT for nuclear medicine applications. Additionally, its performance in diagnostic and therapeutic medical devices was tested. Exposure to computer tomography X-rays resulted in a linear current density with applied voltage, confirming the detectors' adherence to Ohm's law, high electron–hole pair concentration, and fast charge-carrier mobility. Testing with 6-MV photon and 6-MeV electron beams demonstrated the linearity between the detector's relative intensity and beam dose, confirming a consistent detector response. This linearity reduces uncertainty in diagnosis and treatment planning, emphasizing the practical benefits of CZT. Repeated trials at various radiation doses verified the accuracy and consistency of the CZT detector. Owing to its broad energy-sensitivity range, high energy resolution, and linear response to photon and electron beams, CZT emerges as a multipurpose candidate for radiation detection, medical imaging, and nuclear medicine applications.
## Introduction
Radiation detection technologies have advanced significantly, playing critical roles in medical imaging, therapeutic applications, industrial inspection, security systems, and space exploration (Knoll, 2010; Lutz, 2007; Milbrath et al., 2008; Owens, 2019). Semiconductors and scintillators, along with modern hardware, software, and artificial intelligence, offer high detection efficiencies (McGregor and Shultis, 2020; Wang et al., 2023). Semiconductor materials are particularly valued in compact, high-performance systems owing to their direct energy conversion capability. However, traditional semiconductors, such as Si and Ge, exhibit limitations in high-energy radiation environments due to their low atomic numbers, narrow bandgaps, and cooling requirements, which affect their detection efficiency and portability (Owens and Peacock, 2004).
Cadmium Zinc Telluride (CdZnTe, CZT) has emerged as a promising alternative to conventional semiconductors for next-generation radiation detectors (Kim et al., 2015, 2021). As an II–VI compound semiconductor, CZT offers a wide bandgap (1.57 eV), high atomic numbers, and high photon conversion efficiency; therefore, it is ideal for precise energy discrimination, requires minimal cooling, and exhibits high radiation hardness. In addition, its high stopping power and density (5.85 g cm−3) enable efficient high-energy radiation detection, which is beneficial for medical imaging and nuclear medicine applications.
The aforementioned advantageous features of CZT are especially relevant in hybrid diagnostic–therapeutic modalities, such as theranostics, which require both low-energy diagnostic imaging and high-energy therapeutic radiation detection (Eisen et al., 1999; Szeles, 2015). Conventional dosimetry systems often use separate devices for diagnosis and therapy, which leads to operational complexity and causes potential calibration errors. The dual functionality of CZT—low-energy diagnostic imaging and high-energy therapeutic radiation detection—simplifies this process, allowing accurate radiation measurement across a broad energy spectrum. This feature also enables miniaturization and real-time data transmission, making CZT suitable for modern medical devices such as computed tomography (CT), Single Photon Emission Computed Tomography (SPECT), and Magnetic Resonance Imaging (MRI) scanners that demand high detection precision and low noise.
Recent advancements in CZT crystal growth, particularly through the vertical Bridgman method, have improved its radiation detection performance (Scheiber, 1996; Sordo et al., 2009). Optimized Te-rich growth conditions reduce crystallographic imperfections and enhance optical and electrical properties, thus improving energy resolution and radiation detection efficiency, which facilitate accurate interpretation of radiation parameters (Bolotnikov et al., 2008; Melnikov, 1999). Owing to its high stopping power, it can be applied in compact devices, drone-based radiation detection, and space exploration without using special cooling systems.
In medical applications, high energy resolution improves diagnostic accuracy while reducing radiation dose and enhancing image quality by minimizing artifacts and noise. The high sensitivity of CZT ensures precise detection of low-energy photons and thus reduces information loss. Maintaining accuracy while adhering to the “as low as reasonably achievable” (ALARA) principle is essential in diagnostic dosimetry. The stability of CZT across diagnostic and therapeutic doses reduces uncertainty and improves the reliability of medical devices, leading to better patient outcomes (Damulira, 2022; Izewska and Rajan, 2005; Kim et al., 2022; Rosenfeld, 2006; Schlesinger et al., 2001; Seco et al., 2014; Szeles, 2004).
In this study, we evaluated the performance of CZT for nuclear medicine applications and investigated its suitability for dosimetry in both diagnostic and therapeutic applications. We assessed the energy resolution, linearity, and sensitivity of CZT across a broad spectral energy range using radioactive isotopes, X-ray beams, and high-energy photon and electron beams. The results demonstrate that CZT offers high radiation-detection efficiencies and can effectively measure diverse radiation energies for various medical and scientific applications.
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/thesis/preliminary-study-of-cdznte-for-multipurpose-radiation-detection-in-broadband-applications.html