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Feb 07, 2019

Thought Leader Profile: Christer Ullberg CTO

- By Jacqueline Wheeler

Christer Ullberg, Direct Conversion’s Chief Technical Officer and the force behind the photon counting ASIC, has always enjoyed creating technology that benefits the wider world. Even as a bright 15-year-old, and keen cross-country skier, he developed a timing device for ski coaching,

“School was pretty easy, which left me lots of time to do other, interesting things,” he says modestly of his first invention. The device was a financial success and Christer came 11th in the Swedish Junior Cross Country Ski Championships.

With the persistent curiosity of the gifted and the drive to see his technological skills make a difference, Christer continued to study and work in parallel. At college, when other students might have been pulling pints, he went looking for a challenge,

“I found a company producing satellite systems and high-altitude balloons for astronomy research,” says Christer of his work for aerospace company ACR AB.

It’s clear he seeks out opportunities that excite him, that he can develop into something that will have an impact.

“I was employee number two when XCounter was based in the University and working out of a single office there,” Christer says of his move to the start-up that evolved into Direct Conversion. I ask what drew Christer to X-rays,

“The idea of detecting every single X-ray photon was really intriguing. To count them one by one and, by doing so, have the potential to bring some real value to people; this particularly triggered my interest.”

“And at first what we worked on was targeted at mammography; the aim was to detect something at the earliest possible point with the lowest dose.”

Which brings us to Christer’s work on the ASIC. This small piece of silicon that carries an intense concentration of electrical functions was developed to detect very small signals for X-ray and is pivotal to the company’s success.

“The ASIC design was originally created for gas which was the media used to stop the X-rays and convert them into electrical signals.”

However, the gas detectors proved expensive to manufacture outside the rarified conditions of the lab.

“When we moved to cadmium telluride detectors, the ASIC faced more challenges but we realised we could re-use our experiences from the gas-based detectors,” Christer reveals. It is at this point that the company found the direction that has underpinned its success. The cadmium telluride detectors, with Christer’s enhanced ASIC, not only generate high-quality images at low dose but are cheaper to manufacture.

Christer and his colleagues are now working on the next generation of ASICs into which they aim to pack new features for more applications. For Christer, what makes these advances possible, however, is Direct Conversion’s unique approach,

“The company is agile in picking up what the customer wants. Even if they request something which isn’t a standard product, we are fast and flexible in coming up with a solution that works for them.”