Section for Biomedical Physics, University Hospital for Radiation Oncology, Tübingen, Germany.
Radiother Oncol. 2010 Sep;96(3):317-24. doi: 10.1016/j.radonc.2010.07.012. Epub 2010 Jul 30.
Positron emission tomography (PET) provides molecular information about the tumor microenvironment in addition to anatomical imaging. Hence, it seems to be highly beneficial to integrate PET data into radiotherapy (RT) treatment planning. Functional PET images can be used in RT planning following different strategies, with different orders of complexity. In a first instance, PET imaging data can be used for better target volume delineation. A second strategy, dose painting by contours (DPBC), consists of creating an additional PET-based target volume which will then be treated with a higher dose level. In contrast, dose painting by numbers (DPBN) aims for a locally varying dose prescription according to the variation of the PET signal. For both dose painting approaches, isotoxicity planning strategies should be applied in order not to compromise organs at risk compared to conventional modern RT treatment. In terms of physical dose painting treatment planning, several factors that may introduce limitations and uncertainties are of major importance. These are the PET voxel size, uncertainties due to image acquisition and reconstruction, a reproducible image registration, inherent biological uncertainties due to biological and chemical tracer characteristics, accurate dose calculation algorithms and radiation delivery techniques able to apply highly modulated dose distributions. Further research is necessary in order to investigate these factors and their influence on dose painting treatment planning and delivery thoroughly. To date, dose painting remains a theoretical concept which needs further validation. Nevertheless, molecular imaging has the potential to significantly improve target volume delineation and might also serve as a basis for treatment alteration in the future.
正电子发射断层扫描（PET）除了提供解剖成像外，还提供肿瘤微环境的分子信息。因此，将 PET 数据整合到放射治疗（RT）治疗计划中似乎非常有益。功能 PET 图像可以按照不同的复杂程度，通过不同的策略用于 RT 计划。首先，PET 成像数据可用于更好地勾画靶区。第二种策略是轮廓剂量绘制（DPBC），包括创建一个额外的基于 PET 的靶区，然后用更高的剂量水平进行治疗。相比之下，根据 PET 信号的变化，数字剂量绘制（DPBN）旨在实现局部变化的剂量处方。对于这两种剂量绘制方法，都应应用等毒性计划策略，以避免与传统现代 RT 治疗相比危及器官。在物理剂量绘制治疗计划方面，有几个可能会带来限制和不确定性的因素非常重要。这些因素包括 PET 体素大小、图像采集和重建引起的不确定性、可重复的图像配准、由于生物和化学示踪剂特性引起的固有生物学不确定性、准确的剂量计算算法以及能够应用高度调制剂量分布的辐射输送技术。为了彻底研究这些因素及其对剂量绘制治疗计划和输送的影响，需要进一步的研究。迄今为止，剂量绘制仍然是一个理论概念，需要进一步验证。尽管如此，分子成像有可能显著改善靶区勾画，并可能成为未来治疗改变的基础。
