Three dimensional image construction of heavy ion CT with use of residual range measurement

本研究的目的是通过分析空间分辨率和对比度分辨率，寻求高速采集和高质量的图像，验证重离子CT图像三维显示的可行性。研制了重离子CT仪。该装置由400Mev/u的^<14>C离子束、计算机可控移程器、荧光屏、ICCD摄像机组成。通过高速距离调制器的使用和采集程序的开发，实现了更高速度的采集。分别分析了荧光屏和CCD摄像机系统的库仑多重散射、模糊对空间分辨率的贡献，并与整体空间分辨率进行了比较。理论关系很好地解释了结果。相对于水的电子密度分辨率为0.02。这与利用噪声传播理论从投影图像上的噪声计算得到的结果一致。在不降低图像空间分辨率的前提下，利用小波理论对图像进行了降噪处理。由于投影数据是用二维探测器获取的，因此可以使用体数据。利用体数据构建表面渲染图。

The aim of this research is to seek high-speed acquisition and high quality image, by analyzing spatial resolution and contrast resolution and to verify the feasibility of three-dimensional display of heavy ion CT image. Heavy ion CT apparatus was developed. The apparatus consisted of ^<14>C ion beam with 400Mev/u, computer controllable range shifter, fluorescent screen, ICCD video camera. Higher speed acquisition was realized with use of high-speed range modulator and with the development of acquisition program. The contributions of Coulomb multiple scattering, blurring at both the fluorescent screen and CCD video camera system to spatial resolution were analyzed separately and compared with overall spatial resolution. Theoretical relation explains well the results. The electron density resolution was measured as 0.02 relative to water. This agrees with that calculated with use of noise propagation theory from the noises on the projection image. Noise was reduced by the image processing applying the wavelet theory without degrading the spatial resolution. As the projection data were acquired with two-dimensional detector, volume data were useable. Surface rendering images were constructed from the volume data.