Revolutionary Imaging Technology Transforms Lung Scanning Process

Imagine lying motionless on your back inside a large hospital scanner for 45 minutes, arms stretched overhead. It doesn’t sound particularly enjoyable. However, this was the reality for patients undergoing lung scans at the Royal Brompton Hospital in London until recently.

Last year, the installation of a cutting-edge device significantly reduced the duration of these examinations to just 15 minutes. This advancement is attributed to both the innovative image processing capabilities of the scanner and a remarkable material known as cadmium zinc telluride (CZT), which enables the machine to generate intricate, three-dimensional images of the lungs.

“The images produced by this scanner are stunning,” states Dr. Kshama Wechalekar, who leads the nuclear medicine and PET department. “It represents an incredible achievement in engineering and physics.”

The CZT utilized in this scanner, which was put in place last August, is manufactured by Kromek, a British enterprise. Kromek stands out as one of the few companies globally capable of producing CZT. Although not widely known, in Dr. Wechalekar’s view, it is spearheading a “revolution” in the field of medical imaging.

This exceptional material boasts a variety of applications, including use in X-ray telescopes, radiation detection devices, and security scanners at airports. Its demand is rapidly increasing.

Dr. Wechalekar and her team utilize this technology to investigate patients’ lungs, searching for numerous small blood clots in individuals suffering from long Covid or identifying larger clots like pulmonary embolisms.

The £1 million scanner detects gamma rays emitted from a radioactive tracer injected into the patient’s system. However, its heightened sensitivity means that less of this radioactive material is required than in the past. “We’ve managed to reduce doses by approximately 30%,” Dr. Wechalekar notes.

Though scanners based on CZT are not entirely new, the introduction of large, whole-body scanners represents a more recent development. While CZT has existed for decades, its manufacturing process is notoriously challenging. “It has taken significant time to reach a stage of industrial-scale production,” explains Arnab Basu, the founding CEO of Kromek.

Within Kromek’s Sedgefield facility, 170 small furnaces are housed in a space that Dr. Basu likens to a “server farm.” A specialized powder is heated in these furnaces until it melts and then solidifies into a single-crystal structure, a process that spans several weeks. “The crystals are meticulously rearranged atom by atom to achieve alignment,” Dr. Basu elaborates.

The resultant CZT acts as a semiconductor, adept at detecting minute photon particles in X-rays and gamma rays with remarkable accuracy—akin to a highly specialized version of the image sensors in modern smartphone cameras. When a high-energy photon impacts the CZT, it triggers an electron, and this electrical signal is utilized to create an image.

Earlier technologies relied on a more complex two-step method, lacking the precision of current systems. “It’s digital,” Dr. Basu describes. “It employs a single conversion step, preserving all vital information such as timing and energy of the incoming X-ray, enabling the creation of color or spectroscopic images.”

Currently, CZT-based scanners are also deployed for detecting explosives at UK airports and screening checked baggage at certain US airports. “We anticipate that CZT will be integrated into hand luggage scanning in the coming years,” he adds.

Securing CZT is not always straightforward, however. Henric Krawczynski from Washington University in St. Louis has previously utilized this material in space telescopes attached to high-altitude balloons. These detectors are capable of capturing X-rays from neutron stars and plasma surrounding black holes.

Prof. Krawczynski seeks ultra-thin, 0.8mm pieces of CZT for his telescopes, as this minimizes background radiation, yielding a clearer signal. “We would like to acquire 17 new detectors,” he states. “But obtaining these thin variants is extremely challenging.”

He has found it difficult to procure CZT from Kromek, as Dr. Basu mentions that their current demand is high. “We support numerous research organizations, making it hard to manage various requests. Each project necessitates a distinct type of detector structure,” he notes.

For Prof. Krawczynski, this situation is not dire—he may opt to utilize existing CZT from past projects or consider cadmium telluride as an alternative for his next endeavor. Nevertheless, he faces larger challenges ahead. His upcoming mission was scheduled to launch from Antarctica in December, but “all dates are currently uncertain” due to the US government shutdown.

Many researchers utilize CZT, including efforts in the UK to significantly upgrade the Diamond Light Source research facility in Oxfordshire, an endeavor costing £500 million. This enhancement aims to bolster capabilities through the integration of CZT-based detectors.

Diamond Light Source operates as a synchrotron, propelling electrons around a massive ring at nearly light speed. The resulting energy lost by these electrons manifests as X-rays, which are directed through beamlines for material analysis.

Recent experiments have focused on examining impurities in melting aluminum, with the potential to enhance recycled aluminum quality. With the Diamond Light Source’s upgrade expected to conclude in 2030, the X-rays produced will be significantly brighter, rendering existing sensors inadequate.

“Investing in these upgrades is pointless if the light they generate cannot be detected,” remarks Matt Veale, group leader for detector development at the Science and Technology Facilities Council, a stakeholder in the Diamond Light Source.

This is precisely why CZT is the preferred material for this initiative.