Preliminary study of monochromatic X-ray CT with synchrotron radiation

从1990年开始，正在开发一种生物医学SR-CT，用于检测高达几杯碘/毫升的示踪物质，以评估与解剖结构相对应的器官的区域血流和代谢的功能。我们的SR-CT系统在大鼠和幻体上进行了可行性测试。[方法和材料]SR-CT系统由旋转x射线快门、硅（111）通道切割单色仪、样品旋转系统、x射线狭缝和探测器系统组成。单色x射线的能量设定为33.28 keV。每个投影的曝光时间设定为25毫秒。投影数为90。实验波束线为筑波特里斯坦堆积环BLNE 5A。x射线探测器采用成像板（IP）。IP数据由激光束读取，并通过10位模数转换器（BAS-2000）进行数字化处理。激光光斑尺寸为100 μ m^2，深度为10位。CT图像由后处理计算机（hp9000）重建。物体是小棒和脑内充满碘的幻像，还有老鼠。[结果]碘k边缘上方图像清晰地显示了充满碘的空洞和沟状影。碘含量为44.8 mum/ml，可微弱检出。该浓度与理论值（59.7杯/毫升碘）相当。但这种可检测的碘剂量比我们的目的（5杯/毫升碘）大了大约10倍。主要原因是IP激光读取系统动态范围差。因此，为了改进系统以检测低造影剂，需要具有宽动态范围（50000）的传感器。大鼠颅骨100 μ m空间分辨率CT图像显示鼻、下颌骨和颅骨结构清晰。SR-CT的最终目标是检测5杯/毫升的碘，并获得像PET研究一样小于5毫米的空间分辨率的脑图像。

From 1990, a biomedical SR-CT to detect tracer material up to a few mug iodine/ml is being developed for functional evaluations of regional blood flow and metabolism of the organs corresponding to their anatomical structures. The feasibility test of our SR-CT system is performed on phantom and rats.[Methods and material] SR-CT system consists of a rotating X-ray shutter, a silicon (111) channel-cut monochromator, a sample rotating system, X-ray slits and a detector system. Energy of monochromatic X-rays is set at 33.28 keV.Exposure time of each projection is set at 25 msec. The number of projection is 90. Experiment beam line is BLNE 5A of Tristan Accumulation Ring in Tsukuba. Imaging plate(IP) is used as the X-ray detector. The IP data is read by laser beam and digitized by 10 bit analog-to-digital converter (BAS-2000). The spot size of laser is 100 mum^2 with a 10 bit depth. CT image is reconstructed by the post-processing computer(HP 9000). Objects are small rod and brain phantom filled with an iodine, and rats.[Results] The image of above iodine K-edge shows the hole and ditch of phantom filled with iodine clearly. The 44.8 mum/ml iodine can be detected faintly. This concentration corresponds well to the theoretical value (59.7 mug/ml iodine). But this detectable dose of iodine is about 10 times larger than that of our purpose (5 mug/ml iodine). Main reason is poor dynamic range of laser reading system of IP.So to improve the system for detecting very low contrast agent, the sensor with wide dynamic range(50000) is needed.CT image of rat skull with 100 mum spatial resolution showed fine structures of nose, mandibular bone and skull. Final goal of this SR-CT is to detect 5 mug/ml iodine and to obtain less than 5 mm spatial resolution of the brain image like a PET study.