Cadmium Zinc Telluride: The Wonder Material Powering a Medical 'Revolution'

Cadmium zinc telluride (CZT), a hard-to-manufacture semiconductor produced by only a handful of companies, is enabling a quiet revolution in medical imaging, science, and security by delivering faster scans, lower radiation doses, and far more precise X-ray and gamma-ray detection. 'You get beautiful pictures from this scanner,' says Dr Kshama Wechalekar, head of nuclear medicine and PET. 'It's an amazing feat of engineering and physics.' The BBC reports: Kromek is one of just a few firms in the world that can make CZT. You may never have heard of the stuff but, in Dr Wechalekar's words, it is enabling a 'revolution' in medical imaging. This wonder material has many other uses, such as in X-ray telescopes, radiation detectors and airport security scanners. And it is increasingly sought-after. Investigations of patients' lungs performed by Dr Wechalekar and her colleagues involve looking for the presence of many tiny blood clots in people with long Covid, or a larger clot known as a pulmonary embolism, for example.

The 1-million-pound scanner works by detecting gamma rays emitted by a radioactive substance that is injected into patients' bodies. But the scanner's sensitivity means less of this substance is needed than before: 'We can reduce doses about 30%,' says Dr Wechalekar. While CZT-based scanners are not new in general, large, whole-body scanners such as this one are a relatively recent innovation. CZT itself has been around for decades but it is notoriously difficult to manufacture. 'It has taken a long time for it to develop into an industrial-scale production process,' says Arnab Basu, founding chief executive of Kromek.

The newly formed CZT, a semiconductor, can detect tiny photon particles in X-rays and gamma rays with incredible precision -- like a highly specialized version of the light-sensing, silicon-based image sensor in your smartphone camera. Whenever a high energy photon strikes the CZT, it mobilizes an electron and this electrical signal can be used to make an image. Earlier scanner technology used a two-step process, which was not as precise. 'It's digital,' says Dr Basu. 'It's a single conversion step. It retains all the important information such as timing, the energy of the X-ray that is hitting the CZT detector -- you can create color, or spectroscopic images.'

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