X-ray Photon-Counting Detector Module boosts scanner

September 06, 2020 //By Nick Flaherty
An X-ray photon-counting detector module (PCDM) developed by CEA-Leti and used in a prototype could revolutionise computed-tomography (CT) scanning
An X-ray photon-counting detector module (PCDM) developed by CEA-Leti and used in a prototype could revolutionise computed-tomography (CT) scanning

CEA-Leti in France has designed a  new generation of PCDM to be integrated into an X-ray CT scanner prototype. The PCDM module has been integrated into a prototype scanner from Siemens Healthineers and shown increased spatial resolution, reducing X-ray exposure to patients, improving image quality by lowering image noise and artifacts, and by distinguishing multiple contrast agents.

X-ray PCDMs based on cadmium telluride (CdTe) allow simultaneous acquisition of high-spatial-resolution and multi-energy images. Higher spatial resolution improves image quality by using a small-pixel size detector, while image noise can obscure features, and artifacts can mimic them. Detecting the energy of all the photons on the sensor provides colour images and allows a precise determination of the atomic number of any chemical elements present in the body.

“The successful early collaboration with CEA-Leti allowed Siemens Healthineers to prototype what the med- tech company sees as the future of detector modules for whole-body CT,” said Jean-Michel Casagrande, the project manager for medical X-ray imaging at CEA-Leti.

X-ray CT scanners use computer-processed combinations of many X-ray measurements taken from different angles to produce cross-sectional images of scanned objects. Current X-ray CT scanners produce images with energy-integrating detectors (EIDs) where the X-ray photons are first converted into visible light using scintillator material, then visible photons produce electronic signals using a photodiode. PCDMs instead directly convert X-ray photons into electronic signals with a higher conversion yield using CdTe pxiels.

While an EID registers the total energy deposited in a pixel during a fixed period of time, a PCDM counts each photon. This improves the contrast-to-noise ratio of the image, and the energy classification of the detected photons can be used to produce a colour image that allows a precise determination of the atomic number of any chemical elements and a distinction of multiple contrast agents present in the body.

The higher spatial resolution from the smaller pixel size generates clearer images of very-fine structures, such as small airways in the lungs, trabeculae in bones, and thin wires in coronary stents than current scanner technology.

Next: Integrating the X-ray sensor

Picture: 
A CdTe sensor developed by CEA-Leti for an X-ray scanner

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