Speaker
Description
X-ray imaging in medicine, industry, and security can be limited by low contrast between materials. Our lab is developing a Simultaneous-Primary-Scatter x-ray imager (SPSxi), akin at a basic level to combining bright field and dark field imaging in microscopy. Radiation from a rotating-anode x-ray tube is collimated into pencil beams using tungsten/copper plates and the object is step-and-shoot raster scanned through the beams. The resulting radiation distributions are recorded by a PerkinElmer XRD 0840 AN13 Gd2O2S flat panel sensor, analysed, and a transmitted image plus a stack of scatter images at different angles out to about 10° are built point-by-point. The spatial resolution of the scatter image is determined by the pencil beam diameter, and thus there is a tradeoff between spatial resolution and scatter signal size. In our original SPSxi design, the pixel sizes of the scatter and primary images were the same, and equal to the distance that the object was stepped between acquisitions, in the neighbourhood of 1 mm.
Here we report on increasing the spatial resolution of the primary image, which is set by different parameters than the scatter image. In our original design, the primary signal was averaged across the pencil beam. In our current design, the intra-beam information is preserved. At the imaging detector, the primary beam exceeds 4 mm in diameter, while the detector element size is 400 μm. Thus a small circular pattern of about 80 samples 400 μm square can be recorded for each x-ray exposure. As the object is stepped through the beam, most object locations are sampled multiple times, by different parts of the primary beam, because the sequential primary beam footprints overlap on the object. We use Python code to position and place the primary beam information into a higher-resolution accumulation matrix. Since the SPSxi acquisition step size is not generally an integer multiple of 400 μm, we use an accumulation matrix with a finer grid, such as 100 μm. To generate the transmission image, the accumulated data are normalized by data from an air scan with no object present. Recent results are shown.
| Keyword-1 | x-ray imaging |
|---|---|
| Keyword-2 | simultaneous primary + scatter |
| Keyword-3 | instrumentation |