This paper presents a proof-of-concept, high-resolution γ-ray camera for nuclear medicine, utilizing a novel cesium lead bromide (CsPbBr3) perovskite semiconductor detector. The research addresses a key limitation in perovskite detectors—charge loss at the crystal surface—by developing a chemical-mechanical polishing technique that creates an ultra-smooth, defect-free interface, enabling near-unity charge collection efficiency and exceptional device stability. The resulting 4x4 pixelated detector, combined with a multi-channel readout system and depth-correction algorithms, achieves record-breaking energy resolutions of 2.5% at 141 keV and 1.0% at 662 keV, outperforming current clinical systems. The camera successfully performs single-photon imaging of a 99mTc radionuclide source, demonstrating high sensitivity and an impressive spatial resolution of 3.2 mm. These findings establish perovskite semiconductors as a practical, low-cost, and high-performance alternative to conventional detectors, paving the way for next-generation nuclear medicine imaging.
Pioneering Perovskite Detectors for High-Resolution Nuclear Medicine Imaging
The Challenge: Modern nuclear medicine, particularly Single-Photon Emission Computed Tomography (SPECT), requires detectors with high energy resolution, sensitivity, and spatial resolution. Current technologies are either limited in performance (scintillators like NaI(Tl)) or prohibitively expensive (semiconductors like CdZnTe or CZT).
A Promising Alternative: This work introduces detectors based on CsPbBr3 perovskite, a semiconductor material that offers the potential for superior performance at a much lower cost. However, its practical use in imaging has been an uncharted territory.
Key Innovation: Surface Perfection: A major breakthrough was eliminating performance-degrading surface defects. A novel chemical-mechanical polishing method using dimethyl sulfoxide (DMSO) was developed to remove microscopic scratches, reducing surface roughness from 15.8 nm to just 5.5 nm. This resulted in highly uniform charge collection and long-term device stability.
Advanced Detector Design: The system utilizes a 4x4 pixelated detector design. This creates a "small pixel effect," where the signal is primarily induced by the movement of holes (positive charges), minimizing the negative impact of electron trapping and producing clean, sharp energy spectra without low-energy "tailing."
Record-Breaking Energy Resolution: The optimized detector achieved state-of-the-art energy resolution (ER), a key metric for distinguishing radiation sources and rejecting scatter.
2.5% ER at 141 keV: Achieved for the medical isotope Technetium-99m (99mTc), superior to the ~5.5% ER of current clinical CZT systems. The best single pixel achieved 2.2%.
1.0% ER at 662 keV: Achieved overall for Cesium-137 (137Cs) after depth correction, with the best single pixel reaching an unprecedented 0.87%.
Successful Single-Photon Imaging: The system's capabilities were validated in imaging tests emulating clinical use.
High Sensitivity: The detector demonstrated a high sensitivity of 0.13%–0.21% cps/Bq when imaging 99mTc point and line sources.
Excellent Spatial Resolution: Using a Derenzo phantom, the system successfully distinguished individual sources spaced 7 mm apart, indicating an impressive spatial resolution of 3.2–3.8 mm.
Key Takeaway: This research successfully demonstrates that perovskite semiconductor detectors are a viable and superior alternative for nuclear medicine. They offer a powerful combination of low cost, exceptional energy resolution, high sensitivity, and excellent stability, positioning them to significantly advance future diagnostic and therapeutic imaging.