The development of monochromatic X-ray computed tomography with synchrotron radiation

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For biomedical diagnosis, a new monochromatic x-ray CT system using synchrotron radiation is being developed to obtain clear images and to detect low contrast materials for quantitative functional evaluation of organs in correspondence with their anatomical structures.The SR-CT system is constructed at the beam line NE-5A of the Tristan Accumulation Ring in Tsukuba (6.5GeV,20-30mA). This system consists of a rotating x-ray shutter, a silicon (111) and silicon (511) double monochromator, an x-ray slits system, a roating object table, an x-ray linear array sensor system and a computer. By this system, the image with x-ray energy from 30 to 52 keV can be obtained to detect various contrast materials (iodine, barium and gadolinum). The x-ray linear arry sensor consists of BGO scintillators and a silicon photo-diode array. The dynamic range of the system is 60000 : 1 with 200mum of the spatial resolution. Image data was digitized by a 16 bit A/D converter and led to the computer. Exposure time of each projection can be changed from 3 ms to longer. Slice thickness of the object can be also adjustable from 0.1 to 3.2 mm using the slit system. Using a unix workstation, a SR-CT image is reconstructed from the line data obtained by x-ray linear array detector. This workstation can perform high speed image reconstruction using graphic accelerator board.Using the double crystal monochromator, the high order x-ray contamination is eliminated. A new CCD detector have some problems at the junction of sensor, and this produced the artifact. As the machine trouble of AR ring occurred in 1994, the experiments of this system could not performed sufficiently. The detailed experiment will be performed in 1995.