Oelfke U, Bortfeld T
Department of Medical Physics, Deutsches Krebsforschungszentrum (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
Technol Cancer Res Treat. 2003 Oct;2(5):401-12. doi: 10.1177/153303460300200505.
Intensity modulated radiotherapy with high enery photons (IMRT) and with charged particles (IMPT) refer to the most advanced development in conformal radiation therapy. Their general aim is to increase local tumor control rates while keeping the radiation induced complications below desired thresholds. IMRT is currently widely introduced in clinical practice. However, the more complicated IMPT is still under development. Especially, spot- scanning techniques integrated in rotating gantries that can deliver proton or light ion-beams to a radiation target from any direction will be available in the near future. We describe the basic concepts of intensity modulated particle therapy (IMPT). Starting from the potential advantages of hadron therapy inverse treatment planning strategies are discussed for various dose delivery techniques of IMPT. Of special interest are the techniques of distal edge tracking (DET) and 3D-scanning. After the introduction of these concepts a study of comparative inverse treatment planning is presented. The study aims to identify the potential advantages of achievable physical dose distributions with proton and carbon beams, if different dose delivery techniques are employed. Moreover, a comparison to standard photon IMRT is performed. The results of the study are summarized as: i) IMRT with photon beams is a strong competitor to intensity modulated radiotherapy with charged particles. The most obvious benefit observed for charged particles is the reduction of medium and low doses in organs at risk. ii) The 3D-scanning technique could not improve the dosimetric results achieved with DET, although 10-15 times more beam spots were employed for 3D-scanning than for DET. However, concerns may arise about the application of DET, if positioning errors of the patient or organ movements have to be accounted for. iii) Replacing protons with carbon ions leads to further improvements of the physical dose distributions. However, the additional degree of improvement due to carbon ions is modest. The main clinical potential of heavy ion beams is probably related to their radiobiological properties.
高能光子调强放射治疗（IMRT）和带电粒子调强放射治疗（IMPT）代表了适形放射治疗的最新进展。它们的总体目标是提高局部肿瘤控制率，同时将放射诱发的并发症控制在期望阈值以下。IMRT目前已广泛应用于临床实践。然而，更为复杂的IMPT仍在研发中。特别是，集成在旋转机架中的点扫描技术，可从任何方向将质子或轻离子束输送至放射靶区，在不久的将来即可实现。我们阐述了调强粒子治疗（IMPT）的基本概念。从强子治疗的潜在优势出发，讨论了IMPT各种剂量递送技术的逆向治疗计划策略。特别值得关注的是远端边缘跟踪（DET）和三维扫描技术。在介绍这些概念之后，给出了一项比较逆向治疗计划的研究。该研究旨在确定如果采用不同的剂量递送技术，质子束和碳离子束在实现物理剂量分布方面的潜在优势。此外，还与标准光子IMRT进行了比较。该研究结果总结如下：i）光子束IMRT是带电粒子调强放射治疗的有力竞争对手。带电粒子最明显的优势是降低了危及器官中的中低剂量。ii）三维扫描技术未能改善DET所取得的剂量学结果，尽管三维扫描所用的束斑比DET多10至15倍。然而，如果必须考虑患者的定位误差或器官运动，DET的应用可能会引发担忧。iii）用碳离子替代质子可进一步改善物理剂量分布。然而，碳离子带来的额外改善程度不大。重离子束的主要临床潜力可能与其放射生物学特性有关。
