F. H. Burr Proton Therapy Center, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
Int J Radiat Oncol Biol Phys. 2010 Feb 1;76(2):624-30. doi: 10.1016/j.ijrobp.2009.06.065.
We completed an implementation of pencil-beam scanning (PBS), a technology whereby a focused beam of protons, of variable intensity and energy, is scanned over a plane perpendicular to the beam axis and in depth. The aim of radiotherapy is to improve the target to healthy tissue dose differential. We illustrate how PBS achieves this aim in a patient with a bulky tumor.
Our first deployment of PBS uses "broad" pencil-beams ranging from 20 to 35 mm (full-width-half-maximum) over the range interval from 32 to 7 g/cm(2). Such beam-brushes offer a unique opportunity for treating bulky tumors. We present a case study of a large (4,295 cc clinical target volume) retroperitoneal sarcoma treated to 50.4 Gy relative biological effectiveness (RBE) (presurgery) using a course of photons and protons to the clinical target volume and a course of protons to the gross target volume.
We describe our system and present the dosimetry for all courses and provide an interdosimetric comparison.
The use of PBS for bulky targets reduces the complexity of treatment planning and delivery compared with collimated proton fields. In addition, PBS obviates, especially for cases as presented here, the significant cost incurred in the construction of field-specific hardware. PBS offers improved dose distributions, reduced treatment time, and reduced cost of treatment.
我们完成了铅笔束扫描（PBS）的实施，这是一种技术，其中一束聚焦的质子束，具有可变的强度和能量，在垂直于束轴的平面上和深度上进行扫描。放射治疗的目的是改善靶区与健康组织的剂量差异。我们通过一个大肿瘤患者来说明 PBS 如何实现这一目标。
我们首次部署的 PBS 使用“宽”铅笔束，其宽度从 20 到 35 毫米（全宽半最大值），范围间隔从 32 到 7 g/cm(2)。这种束刷为治疗大体积肿瘤提供了独特的机会。我们介绍了一个大的（4295cc 临床靶体积）腹膜后肉瘤的病例研究，该肉瘤使用光子和质子治疗临床靶体积，以及质子治疗大体靶体积，达到 50.4Gy 相对生物学效应（RBE）（术前）。
我们描述了我们的系统，并提供了所有课程的剂量学，并进行了课程间的比较。
与准直质子场相比，PBS 用于大体积肿瘤可降低治疗计划和交付的复杂性。此外，PBS 消除了，特别是对于这里提出的情况，在构建特定于字段的硬件方面所产生的巨大成本。PBS 提供了更好的剂量分布，缩短了治疗时间，并降低了治疗成本。
