VIDEO: Photon-counting CT development at the University of Wisconsin

The university is partnering with GE Healthcare in the development of a new type of deep silicon photon-counting detector technology. GE has had other prototype photon-counting detectors (PCD), none were commercialized. The vendor decided to move in a new direction with this technology, where the University of Wisconsin is now leading the research.

GE, like all the key CT vendors that are working on PCD technology, hopes to commercial photon-counting CT in a premium system in the next few years. Siemens was the first to market with a PCD CT in 2021, and the second system to gain FDA was the Samsung OmniTom Elite head CT scanner, displayed for the first time at RSNA 2022. Szczykutowicz said the detector technology will likely differentiate GE. 

"The detector we are developing is based on silicon, which is different than other typos of photon-counting detectors in that silicon has a low atomic number, Szczykutowicz explained. "Some of the other vendors that have cleared, or are developing, photon-counting detectors use cadmium-telluride, or radium-zinc-telluride. So that is the major difference, using silicon versus heavier element-based detectors."

He said preclinical studies they conducted and imaging with the first FDA-cleared PCD system show image quality with PCD CT is much better that the current generation of CT scanners. 

"You are seeing much better image detail, lower radiation doses, better quantification of CT numbers that you can trust, better imaging of bariatric patients, not so many issues with photon starvation and noise streaking, and all those types of things that make a radiologist's job harder," Szczykutowicz explained. "We are seeing lots of signs that photon-counting can do lots of things better."

PCDs also have inherent spectral imaging capabilities built into every scan, because the detectors bin the photons of different energies. This allows radiologists to retrospectively look at images at different energy levels to enhance contrast. The spectral capability also allows dialing out of periodic elements like iodine, calcium and metals in implants to eliminate metal artifacts, see the lumen inside calcified or stented arteries, or create non-contrast scans from contrast images.

He said this may help overcome the workflow issues and required pre-planning for current spectral CT scans that hampers wider use of the spectral imaging.

PCD technology has been researched for years, but it also created new technology hurtles that needed to be overcome. This includes how to handle a much larger stream of data from the scanner and directing different energy photons into different bin counts takes a lot of computer processing power. The development of the electronic components that work with the PCDs have also been a work-in-progress, with sessions devoted to the topic at the medical physics conferences he has attended for the past several years. 

He said this push into developing this new photon-counting CT detector technology has been a few years in the making, with the university serving on GE advisory boards and publishing a few high-level research papers. But in 2022, he said, it became much more serious with the installation of the first research scanner using the technology at the University of Wisconsin Madison. 

The new system began scanning its first human patients the week of Thanksgiving just before RSNA.