Institut Interdisciplinaire d'Innovation Technologique (3IT), Université de Sherbrooke, Sherbrooke, Québec, Canada. Département de Génie Électrique et Génie Informatique, Université de Sherbrooke, Sherbrooke, Québec, Canada.
Phys Med Biol. 2020 Apr 22;65(8):085013. doi: 10.1088/1361-6560/ab78bf.
Computed tomography has greatly improved over the last decade, especially through x-ray dose exposure reduction while maintaining image quality. Herein, a new concept is proposed to improve the contrast-to-noise ratio (CNR) by including the time-of-flight (TOF) information of individual photons to obtain further insight on the photon's trajectory and to reject scatter contribution. The proof of the concept relies on both simulation and experimental measurements in a cone-beam computed tomography arrangement. Results show a statistical difference between the TOF of scattered and primary photons exploitable in TOF computed tomography. For a large volume of the size of a human abdomen, a scatter reduction from 296% to 4% is achieved in our simulation setup with perfect timing measurements which yields a 110% better CNR, or a dose reduction by a factor of four. Cup artifacts are also reduced from 24.7% to 0.8%, and attenuation inaccuracies are improved from -26.3% to -0.8%. With 100 ps and 10 ps FWHM timing jitters, respectively 75% and 95% of the scatter contribution can be removed with marginal gains below 10 ps. Experimental measurements confirm the feasibility of measuring statistical differences between the TOF of scattered and primary photons.
在过去的十年中，计算机断层扫描技术有了很大的改进，特别是通过减少 X 射线剂量暴露，同时保持图像质量。在此，提出了一种新的概念，通过包括单个光子的飞行时间 (TOF) 信息来提高对比噪声比 (CNR)，以进一步了解光子的轨迹并拒绝散射贡献。该概念的验证依赖于在锥形束计算机断层扫描装置中的模拟和实验测量。结果表明，在 TOF 计算机断层扫描中，散射和原始光子的 TOF 之间存在可利用的统计差异。在我们的模拟设置中，对于一个人体腹部大小的大体积，通过完美的定时测量，散射减少了 296%至 4%，这使得 CNR 提高了 110%，或者剂量减少了四倍。杯状伪影也从 24.7%减少到 0.8%，衰减误差从-26.3%提高到-0.8%。分别具有 100 ps 和 10 ps FWHM 定时抖动时，通过 10 ps 以下的微小增益，可以去除 75%和 95%的散射贡献。实验测量证实了测量散射和原始光子的 TOF 之间的统计差异的可行性。
