Hong L, Goitein M, Bucciolini M, Comiskey R, Gottschalk B, Rosenthal S, Serago C, Urie M
Department of Radiation Oncology, Massachusetts General Hospital, Boston, USA.
Phys Med Biol. 1996 Aug;41(8):1305-30. doi: 10.1088/0031-9155/41/8/005.
The sharp lateral penumbra and the rapid fall-off of dose at the end of range of a proton beam are among the major advantages of proton radiation therapy. These beam characteristics depend on the position and characteristics of upstream beam-modifying devices such as apertures and compensating boluses. The extent of separation, if any, between these beam-modifying devices and the patient is particularly critical in this respect. We have developed a pencil beam algorithm for proton dose calculations which takes accurate account of the effects of materials upstream of the patient and of the air gap between them and the patient. The model includes a new approach to picking the locations of the pencil beams so as to more accurately model the penumbra and to more effectively account for the multiple-scattering effects of the media around the point of interest. We also present a faster broad-beam version of the algorithm which gives a reasonably accurate penumbra. Predictions of the algorithm and results from experiments performed in a large-field proton beam are presented. In general the algorithm agrees well with the measurements.
质子束尖锐的外侧半影以及在射程末端剂量的快速下降是质子放射治疗的主要优势之一。这些束流特性取决于上游束流修正装置（如孔径和补偿 bolus）的位置和特性。在这方面，这些束流修正装置与患者之间的分离程度（若有）尤为关键。我们开发了一种用于质子剂量计算的笔形束算法，该算法能准确考虑患者上游材料的影响以及它们与患者之间气隙的影响。该模型包括一种新的选择笔形束位置的方法，以便更准确地模拟半影，并更有效地考虑感兴趣点周围介质的多重散射效应。我们还展示了该算法的一个更快的宽束版本，它能给出相当准确的半影。给出了该算法的预测结果以及在大视野质子束中进行的实验结果。总体而言，该算法与测量结果吻合良好。
