CT scanners computer-process combinations of many X-ray images taken from different angles to produce 3D data.
“Current x-ray CT scanners produce images with energy-integrating detectors [EIDs], which are based on indirect conversion technology: X-ray photons are first converted into visible light using scintillator material, then visible photons produce electronic signals using a photodiode,” according to Leti. “Photon-counting detector module, on the other hand, directly convert x-ray photons into electronic signals with a higher conversion yield.”
While EIDs register the total energy deposited in a pixel during a fixed period of time, producing a monochrome image indicating density of the body’s organs, PCDMs count each photon and allow photon energy to be classified, allowing “a precise determination of the atomic number of any chemical elements and a distinction of multiple contrast agents present in the body”, said Leti.
The device has been integrated into an x-ray scanner prototype from Siemens Healthineers, which invented the concept.
“The idea of Siemens Healthineers to integrate PCDMs in the x-ray CT scanners was new and no available technology existed when CEA-Leti began working on this,” said CEA-Leti industrial partnership manager Loick Verger. “The technical challenge – low noise at high counting rate, two energy classifications, and sufficient maturity to be integrated in an X-ray CT scanner – was tremendous.”
The US Mayo Clinic has tried Siemens’ machine.
“Images of more than 300 patients produced with this technology consistently demonstrated that the theoretical benefits of this type of detector technology yield a number of important clinical benefits,” Mayo Clinic professor of medical physics Cynthia McCollough. “Publications by our research team have shown improved spatial resolution, decreased radiation or iodine contrast dose requirements, and decreased levels of image noise and artifacts. Additionally, the ability to simultaneously acquire multiple 150μm resolution datasets, each representing a different energy spectrum, is anticipated to lead to new clinical applications.”