University of Surrey, Guildford, Surrey, UK.
Phys Med Biol. 2012 Feb 7;57(3):665-83. doi: 10.1088/0031-9155/57/3/665. Epub 2012 Jan 12.
Optical computed tomography has now become a well-established method for making empirical measurements of 3D dose distributions in radiotherapy treatment verification. The requirement for effective refractive index matching as part of the scanning process has long been an inconvenience for users, limiting the speed of sample throughput. We propose a new method for reconstructing data that takes explicit account of the refracted path of the light rays and demonstrate theoretically the conditions under which there are sufficient data to create a good reconstruction. Examples of the performance of the algorithm are given. For smoothly varying data, reconstructed images of very high quality are obtained, with RMS deviation of under 1% from the original, provided that the irradiated region lies entirely within a critical radius. For the dosimeter material PRESAGE, this critical value is approximately 0.65 of the sample radius. Regions outside this are not reconstructed successfully, but we argue that there are many cases where this disadvantage is outweighed by the benefits of the technique.
光学计算机断层扫描现已成为一种成熟的方法，可用于对放射治疗验证中的三维剂量分布进行经验测量。作为扫描过程的一部分，有效折射率匹配的要求长期以来一直使用户感到不便，限制了样品通量的速度。我们提出了一种新的数据重建方法，该方法明确考虑了光线的折射路径，并从理论上证明了存在足够数据以进行良好重建的条件。给出了算法性能的示例。对于平滑变化的数据，即使原始数据的 RMS 偏差小于 1%，也可以获得非常高质量的重建图像，前提是辐照区域完全位于临界半径内。对于剂量计材料 PRESAGE，此临界值约为样品半径的 0.65。在此之外的区域无法成功重建，但我们认为在许多情况下，该技术的优势超过了其缺点。
