Now, scientists led by Northwestern University and Soochow University in China have built the first perovskite-based detector that can capture individual gamma rays for SPECT imaging with record-breaking precision. The new tool could make common types of nuclear medicine imaging sharper, faster, cheaper and safer.

For patients, that could mean shorter scan times, clearer results and lower doses of radiation.

The study was published on Aug. 30 in the journal Nature Communications.

"Perovskites are a family of crystals best known for transforming the field of solar energy," said Northwestern's Mercouri Kanatzidis, the study's senior author. "Now, they are poised to do the same for nuclear medicine. This is the first clear proof that perovskite detectors can produce the kind of sharp, reliable images that doctors need to provide the best care for their patients."

"Our approach not only improves the performance of detectors but also could lower costs," said co-corresponding author Yihui He, a professor at Soochow University. "That means more hospitals and clinics eventually could have access to the best imaging technologies."

Kanatzidis is a Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern's Weinberg College of Arts and Sciences and a senior scientist at Argonne National Laboratory. Yihui He is a former postdoctoral fellow from Kanatzidis' laboratory.

Nuclear medicine, like SPECT (single-photon emission computing tomography) imaging, works like an invisible camera. Physicians implant a tiny, safe, short-lived radiotracer in a specific part of a patient's body. The tracer emits gamma rays, which pass outward through tissues and eventually hit a detector outside of the body. Each gamma ray is like a pixel of light. After collecting millions of these pixels, computers can construct a 3D image of working organs.

Today's detectors, which are either made from cadmium zinc telluride (CZT) or sodium iodide (NaI), have several disadvantages. CZT detectors are incredibly expensive, sometimes reaching into the price range of hundreds of thousands to millions of dollars for a whole camera. Because CZT crystals are brittle and prone to cracking, these detectors also are difficult to manufacture. While cheaper than CZT detectors, NaI detectors are bulky and produce blurrier images -- like taking a photo through a foggy window.

To overcome these issues, the scientists turned to perovskite crystals, a material that Kanatzidis has studied for more than a decade. In 2012, his group built the first solid-film solar cells made from perovskites. Then, in 2013, Kanatzidis discovered that single perovskite crystals were highly promising for detecting X-rays and gamma rays. This breakthrough, enabled by his group's growth of high-quality single crystals, sparked a worldwide surge of research and effectively launched a new field in hard radiation detection materials.

"This work demonstrates how far we can push perovskite detectors beyond the laboratory," Kanatzidis said. "When we first discovered in 2013 that perovskite single crystals could detect X-rays and gamma rays, we could only imagine their potential. Now, we're showing that perovskite-based detectors can deliver the resolution and sensitivity needed for demanding applications like nuclear medicine imaging. It's exciting to see this technology moving closer to real-world impact."

Building on this foundation, Kanatzidis and He led the crystal growth, surface engineering and device design for the new study. By carefully growing and shaping these crystals, the researchers created a pixelated sensor -- just like the pixels in a smartphone camera -- that delivers record-breaking clarity and stability.

Leading the design and development of the prototype gamma-ray detector, He developed the camera's pixelated architecture, optimized the multi-channel readout electronics and carried out the high-resolution imaging experiments that validated the device's capabilities. He, Kanatzidis and their team demonstrated that perovskite-based detectors can achieve record energy resolutions and unprecedented single-photon imaging performance, paving the way for practical integration into next-generation nuclear medicine imaging systems.

"Designing this gamma-ray camera and demonstrating its performance has been incredibly rewarding," He said. "By combining high-quality perovskite crystals with a carefully optimized pixelated detector and multi-channel readout system, we were able to achieve record-breaking energy resolution and imaging capabilities. This work shows the real potential of perovskite-based detectors to transform nuclear medicine imaging."

In experiments, the detector was able to differentiate among gamma rays of different energies with the best resolution reported thus far. It also sensed extremely faint signals from a medical radiotracer (technetium-99m) commonly used in clinical practice and distinguished incredibly fine features, producing crisp images that could separate tiny radioactive sources spaced just a few millimeters apart. The detector also remained highly stable, collecting nearly all the tracer's signal without loss or distortion. Because these new detectors are more sensitive, patients potentially could require shorter scan times or smaller doses of radiation.

Northwestern spinout company Actinia Inc. is commercializing this technology -- working with partners in the medical device field to bring it out of the lab and into hospitals. Because they are easier to grow and use simpler components, perovskites offer a far less expensive alternative to CZT and NaI detectors without sacrificing quality. Perovskite-based detectors also offer a realistic pathway to imaging using a lower dose of a radiotracer than can be used with a NaI detector but at a price that ensures widespread patient access.

"Demonstrating that perovskites can deliver single-photon gamma-ray imaging is a milestone," He said. "It shows these materials are ready to move beyond the laboratory and into technologies that directly benefit human health. From here, we see opportunities to refine the detectors further, scale up production and explore entirely new directions in medical imaging."

"High-quality nuclear medicine shouldn't be limited to hospitals that can afford the most expensive equipment," Kanatzidis said. "With perovskites, we can open the door to clearer, faster, safer scans for many more patients around the world. The ultimate goal is better scans, better diagnoses and better care for patients."

The study, "Single photon γ-ray imaging with high energy and spatial resolution perovskite semiconductor for nuclear medicine," was supported by the Defense Threat Reduction Agency (award number HDTRA12020002), the Consortium for Interaction of Ionizing Radiation with Matter University Research Alliance, the National Key R&D Program of China (award number 2021YFF0502600), the National Natural Science Foundation of China (award number U2267211) and the Jiangsu Natural Science Foundation (award number BK20240822).