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Faster lung scans thanks to advanced detector material
Patients at Royal Brompton Hospital in London no longer endure 45-minute lung scans after the installation of a new scanner that completes the procedure in just 15 minutes. The upgrade, introduced last August, relies on cadmium zinc telluride (CZT), a semiconductor that enhances image clarity while reducing radiation exposure.
How the technology works
The £1 million device detects gamma rays emitted by a radioactive tracer injected into patients. Its high sensitivity allows for a 30% reduction in the required dose, according to Dr. Kshama Wechalekar, head of nuclear medicine and PET at the hospital. The CZT-based scanner captures highly detailed 3D images of the lungs, aiding in the detection of conditions like pulmonary embolisms and blood clots linked to long Covid.
"You get beautiful pictures from this scanner. It's an amazing feat of engineering and physics."
Dr. Kshama Wechalekar, Royal Brompton Hospital
Challenges in producing CZT
Despite its advantages, CZT is difficult to manufacture. Kromek, the UK-based company behind the hospital's scanner, operates 170 small furnaces at its Sedgefield facility to produce the material. The process involves melting a specialized powder and solidifying it into a single-crystal structure over several weeks. Each atom must align perfectly to create the semiconductor, which detects X-rays and gamma rays with precision.
Arnab Basu, Kromek's CEO, explains that the material enables a single-step digital conversion, preserving critical data like photon energy and timing. This allows for spectroscopic imaging, a feature absent in older, two-step scanners.
Broader applications and supply constraints
CZT is already used in UK airport security for explosives detection and in some US airports for checked baggage scans. Kromek expects the technology to expand to hand luggage screening within a few years. However, demand outstrips supply, with researchers like Henric Krawczynski at Washington University struggling to source thin CZT detectors for X-ray telescopes.
Krawczynski, who studies neutron stars and black holes, requires 0.8mm-thick CZT to minimize background radiation interference. Unable to secure the material from Kromek, he may resort to alternatives like cadmium telluride for his next mission, delayed by the US government shutdown.
Future of CZT in scientific research
The material is also critical for the £500 million upgrade of the Diamond Light Source in Oxfordshire, a synchrotron facility that generates ultra-bright X-rays for material analysis. Existing sensors would be overwhelmed by the increased brightness post-upgrade, making CZT detectors essential.
"There's no point in spending all this money upgrading these facilities if you can't detect the light they produce."
Matt Veale, Science and Technology Facilities Council
The upgrade, set for completion in 2030, will enable experiments like probing impurities in molten aluminium, potentially improving recycling processes for the metal.
