Huizenga H, Storchi P R
Acta Radiol Oncol. 1985 Nov-Dec;24(6):509-19. doi: 10.3109/02841868509134425.
Although corrections for 'beam hardening' and 'scattering' have been implemented in currently available CT scanners, systematic differences exist between a real CT image and an ideal, artefact-free and monochromatic image. The appearance and magnitude of these differences are discussed. Conversion to the ideal image, i.e. conversion from CT number to X-ray attenuation coefficient at diagnostic photon energies, turns out to be possible with an accuracy of 5 per cent. In order to use the CT 'density' information from patients, in clinical photon and electron beam dose calculations, conversions must be made from the X-ray attenuation coefficient at diagnostic energies to relevant high energy radiation interaction properties. These conversions turn out to be possible within an accuracy also of 5 per cent. These limited accuracies cause errors in the photon beam dose calculation of less than 1 per cent of the dose maximum and errors in electron beam dose calculations of less than 2 per cent of the dose maximum.
尽管目前可用的CT扫描仪已对“束硬化”和“散射”进行了校正，但真实的CT图像与理想的、无伪影的单色图像之间仍存在系统差异。本文讨论了这些差异的表现形式和大小。结果表明，将CT图像转换为理想图像，即在诊断光子能量下从CT值转换为X射线衰减系数，其精度可达5%。为了在临床光子和电子束剂量计算中使用来自患者的CT“密度”信息，必须将诊断能量下的X射线衰减系数转换为相关的高能辐射相互作用特性。结果表明，这些转换的精度也可达5%。这些有限的精度导致光子束剂量计算中的误差小于剂量最大值的1%，电子束剂量计算中的误差小于剂量最大值的2%。
