Friday, February 17th, 2012
The benefits of slot scanning x-rays were described in an earlier blog. This approach has the major advantage of reducing x-ray scatter, increasing signal-to-noise ratio and so improving image quality, while at the same time reducing the dose to which the patient is exposed. About eighteen months ago we at CapeRay decided to design and build our own digital x-ray camera to take advantage of the slot scanning geometry.
And so the Pandia was conceived. The name has its origins in Greek mythology where the goddess Pandia was the personification of brightness. She was also known as the goddess of the full moon and her beauty was renowned among the gods. So, how did we go about designing our digital x-ray camera and does it live up to the promise of its name?
The Pandia is based on a charged-coupled device (CCD) that operates in time delay and integration (TDI) mode in which the moving camera integrates the image of each line over several rows of sensors, thus gathering more light per exposure. We have used two types of scintillator material – either Cesium Iodide or Gadolinium Oxide – to convert the x-rays into light. Our sensor consists of square pixels with a size of 27 μm and a resolution of 8,520 x 242 pixels, yielding a static imaging area of 230.0 x 6.5 mm. By way of comparison, the camera in the iPhone 4S has a pixel size of 1.4 μm and a resolution of 3,264 x 2,448 pixels (i.e. approximately 8 megapixels).
In dynamic scanning mode, Pandia covers an area of 230.0 x 300.0 mm, acquiring an image of 8,520 x 11,111 pixels (i.e. almost 95 megapixels) in just six seconds at a data capture rate approaching 40 MegaBytes per second. This throughput is accomplished via a high-speed interface based on the GigaBit Ethernet protocol, providing plug-and-play functionality.
Our Pandia digital x-ray camera has been designed for a variety of scanning applications, including mammography, dental imaging, bone density and, in an industrial setting, non-destructive testing. It is currently undergoing final testing before we register it for the CE mark in the next few months.