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THUWAL, Saudi Arabia — Anyone who’s ever gone to the dentist remembers that unnerving moment when a technician puts a heavy lead vest over them and runs out of the room to take their X-rays. Thankfully, there may finally be a safer way to take these scans without all the radiation exposure.
A team of researchers at King Abdullah University of Science and Technology (KAUST) may have cracked the code for maintaining high-quality imaging with less radiation exposure. They have developed a novel technique that can drastically lower the radiation dose needed for X-ray imaging without compromising image quality.
The study, published in the journal ACS Central Science, details how the researchers engineered a “cascade” of interconnected single-crystal devices to create X-ray detectors with significantly improved performance compared to traditional methods.
“This advancement reduces detection limits and paves the way for safer and more energy-efficient medical imaging and industrial monitoring,” says Omar F. Mohammed, the corresponding author of the study, in a media release. “It demonstrates that cascade-engineered devices enhance the capabilities of single crystals in X-ray detection.”
The key innovation lies in the cascade configuration, which involves connecting multiple single-crystal devices in series. This setup allows the detectors to maintain the same signal current generated by X-ray exposure while dramatically reducing the unwanted “dark current” that contributes to background noise.
Typically, X-ray detectors struggle to distinguish the actual X-ray signal from background noise, forcing medical professionals to use higher radiation doses to obtain usable images. However, the cascade approach developed by the KAUST team resolved this issue, reducing the detection threshold from 590 nanograys per second (nGy/s) with a conventional single-crystal device down to just 100 nGy/s.
To test the cascade devices, the researchers used methylammonium lead bromide (MAPbBr3) perovskite single crystals, a relatively new material that has shown great promise for X-ray detection due to its excellent charge transport properties. They fabricated four identical MAPbBr3 crystals and connected them in series, creating devices labeled SC1, SC1-2, SC1-3, and SC1-4 to reflect the number of cascaded crystals.
Through a series of experiments, the team demonstrated that the cascade configuration consistently outperformed the single-crystal device. Not only did SC1-2 exhibit the lowest detection limit, but it also achieved the highest spatial resolution of 8.5 line pairs per millimeter – significantly better than the 5.6 lp/mm achieved by the single-crystal SC1 device.
Importantly, the researchers validated that their cascade method works across different applied voltages and material thicknesses, as well as for other semiconductor materials like cadmium telluride (CdTe). This versatility suggests the technique could have widespread applicability in the field of X-ray detection.
With the potential to transform medical diagnostics, the cascade-engineered X-ray detectors developed by the KAUST team represent a significant step forward in the quest to reduce radiation exposure without compromising image quality. By harnessing the unique properties of perovskite materials and a clever engineering approach, these researchers have opened up new avenues for safer, more effective X-ray technology.
Paper Summary
Methodology
The researchers grew high-quality MAPbBr3 perovskite single crystals using a temperature-controlled crystallization method. They selected four identical crystals, each measuring 3 x 3 mm with a thickness of 2 mm, and conducted a comprehensive characterization of their structural, optical, and electronic properties to ensure consistent performance across the samples.
To test the cascade configuration, the team connected the four MAPbBr3 crystals in series, creating devices with one (SC1), two (SC1-2), three (SC1-3), and four (SC1-4) cascaded crystals. They then subjected these devices to various X-ray dose rates and measured their performance in terms of dark current, signal current, sensitivity, signal-to-noise ratio (SNR), and spatial resolution.
Key Results
The cascade approach demonstrated significant advantages over the single-crystal device (SC1). The dark current of SC1-2 was nearly half that of SC1, and this trend continued as more crystals were added in series, with SC1-4 exhibiting the lowest dark current.
The detection limit, which represents the lowest X-ray dose that can be reliably detected, was also drastically improved in the cascade devices. SC1-2 achieved a detection limit of 100 nGy/s, a six-fold reduction compared to the 590 nGy/s limit of the single-crystal SC1 device.
Study Limitations
The study was limited to a relatively small sample size of four MAPbBr3 single crystals, though the researchers did demonstrate the versatility of the cascade approach by testing it with CdTe single crystals as well. Additionally, the cascade configuration with three or more crystals showed some performance degradation, likely due to increased resistance and reduced charge transfer efficiency over longer series connections.
Discussion & Takeaways
The cascade-engineered X-ray detectors developed by the KAUST team represent a significant advancement in the field of low-dose X-ray imaging. By leveraging the unique properties of perovskite materials and a clever engineering approach, the researchers were able to dramatically improve the signal-to-noise ratio and detection limits of X-ray detectors without compromising sensitivity or spatial resolution.
The cascade configuration’s ability to maintain signal current while reducing dark current is the key innovation that enables this performance boost. This approach could have far-reaching implications for medical imaging, security screening, and other applications where minimizing radiation exposure is of utmost importance.
Importantly, the researchers demonstrated the versatility of their cascade method, showing that it can be applied to different semiconductor materials and device configurations. This suggests the technique could be widely adopted and adapted to suit various low-dose X-ray detection needs.
Funding & Disclosures
This work was supported by the King Abdullah University of Science and Technology (KAUST). The authors declare no competing financial interests.
