Lying on your back inside a large hospital scanner as far as possible with your arms above your head for 45 minutes is not the most fun. That’s what they had to do Patients at the Royal Brompton Hospital in London during certain lung scanuntil the hospital installed a new device last year cut these exams down to just 15 minutes.
This is partly due to the scanner’s image processing technology, but also due to a a special material known as CZT (abbreviation in English for cadmium zinc telluride), which allows the machine create three-dimensional images with high detail light patients.
“With this scanner you will get beautiful images,” says Dr. Kshama Vehalekar, head of nuclear medicine and PET (positron emission tomography), adding, “This is a real feat of engineering and physics.”
The CZT machine installed in the hospital in August was manufactured by Kromeka British company, one of the few in the world that can produce it. You may never have heard of it, but in Vechalekar’s words, it causes a a “revolution” in medical imaging.
The wonderful material also has many other uses, e.g X-ray telescopes, radiation detectors in airport security scanners. And it is increasingly in demand.
A study of lung patients by Dr. Vehalekar and her colleagues includes note the presence of multiple blood clots tiny ones in people with long-standing covid or a larger clot known as a pulmonary embolism, for example.
A million pound scanner (about US$1.4 million), works by detecting gamma rays emitted by a radioactive substance that is injected into the patients’ body. But the sensitivity of the scanner means that less of this substance is required than before. “We can reduce the doses by about 30%,” says the doctor.
While CZT-based scanners in general are not new, large whole-body scanners like this one are a relatively recent innovation. CZT has been around for decades but Its production is known to be difficult.
“It takes a lot of time to turn it into an industrial manufacturing process,” says Arnab Basu, founding CEO of Kromek. The company’s facilities in Sedgefield, England, have 170 small ovens in a facility that Dr. Basu describes as “like a server farm.”
In these ovens a special powder is heated, melted and then solidified forming a single crystal structure. The whole process takes weeks. “Atom by atom, the crystals are rearranged (…) until they are completely aligned,” Basu explains.
A newly created CZT semiconductor can detect tiny photonic particles in X-rays and gamma rays with incredible precision, like a highly specialized version of the photosensitive silicon image sensor found in your smartphone’s camera.
Whenever a high-energy photon hits the CZT, it mobilizes an electron, and this electrical signal can be used to create an image. Previous scanner technology used a two-step process that It was not so accurate.. “It’s digital,” says Basu.
“This is a single conversion step. It stores all the important information, such as the time and energy of the X-rays hitting the CZT detector; color or spectroscopic images can be produced,” he adds.
He adds that CZT-based scanners are currently used to detect explosives at UK airports and to scan checked baggage at some US airports: “We expect CZT to enter the carry-on segment in the coming years.”
Selected material
But It is not always easy to get a CZT. Henrik Krawczynski from Washington University in St. Louis (USA) has already used the material earlier in space telescopes tied to high-altitude balloons.
These detectors can pick up X-rays from both neutron stars and the plasma around black holes.
Professor Krawczynski needs very thin pieces of CZT, 0.8 mm, for his telescopes, as this helps reduce the amount of background radiation they pick up. allows for a clearer signal. “We’d like to buy 17 new detectors,” he says, lamenting, “It’s really hard to make them thin.”
Cromek could not help him because, according to Basu, Your company is in high demand right now. “We support a lot of research organizations,” he adds, “it’s very difficult for us to do a hundred different things.” Each research project requires a special type of detector.”
A pair of Kravchinskys, This is not a crisis: Says that for the next mission you could use CZT obtained from previous research, or cadmium telluride, an alternative. however, now there are more serious problems.
The next mission was supposed to leave Antarctica in December, but “all the dates are changing,” Krawczynski says, because of the U.S. government shutdown in November. Many other scientists use CZT.
U Great Britaina major upgrade of the Diamond Light Source research center in Oxfordshire will improve its capabilities by installing CZT-based detectors.
Diamond light source It’s a synchrotron that shoots electrons around a giant ring at close to the speed of light. The magnets cause these electrons to lose energy as X-rays as they whiz by, and they are directed out of the ring into lines of light, for example for materials analysis.
Some recent experiments have involved analyzing impurities in aluminum as it is smelted. You can better understand these impurities help improve recycled metal forms.
With the Diamond Light Source upgrade, whose Completion is planned for 2030the x-rays produced will be much brighter, meaning that existing sensors will not be able to detect them properly.
“There’s no point in spending all this money upgrading these facilities if you can’t detect the light they’re producing,” says Matt Weil, head of the detector development group at the Science and Technology Facilities Council, a member of Diamond Light Source. Thus, CZT is the material of choice here as well.
Lt. Chris Baraniuk
