新型西门子多叶准直器160 MLC的6兆伏剂量学特性

6 MV dosimetric characterization of the 160 MLC, the new Siemens multileaf collimator.

作者信息

Tacke Martin B, Nill Simeon, Häring Peter, Oelfke Uwe

机构信息

Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.

出版信息

Med Phys. 2008 May;35(5):1634-42. doi: 10.1118/1.2889782.

DOI:10.1118/1.2889782

PMID:18561638

Abstract

New technical developments constantly aim at improving the outcome of radiation therapy. With the use of a computer-controlled multileaf collimator (MLC), the quality of the treatment and the efficiency in patient throughput is significantly increased. New MLC designs aim to further enhance the advantages. In this article, we present the first detailed experimental investigation of the new 160 MLC, Siemens Medical Solutions. The assessment included the experimental investigation of typical MLC characteristics such as leakage, tongue-and-groove effect, penumbra, leaf speed, and leaf positioning accuracy with a 6 MV treatment beam. The leakage is remarkably low with an average of 0.37% due to a new design principle of slightly tilted leaves instead of the common tongue-and-groove design. But due to the tilt, the triangular tongue-and-groove effect occurs. Its magnitude of approximately 19% is similar to the dose defect measured for MLCs with the common tongue-and-groove design. The average longitudinal penumbra measured at depth d(max) = 15 mm with standard 100 x 100 mm2 fields is 4.1 +/- 0.5 mm for the central range and increases to 4.9 +/- 1.3 mm for the entire field range of 400 x 400 mm2. The increase is partly due to the single-focusing design and the large distance between the MLC and the isocenter enabling a large patient clearance. Regarding the leaf speed, different velocity tests were performed. The positions of the moving leaves were continuously recorded with the kilovoltage-imaging panel. The maximum leaf velocities measured were 42.9 +/- 0.6 mm/s. In addition, several typical intensity-modulated radiation therapy treatments were performed and the delivery times compared to the Siemens OPTIFOCUS MLC. An average decrease of 11% in delivery time was observed. The experimental results presented in this article indicate that the dosimetric characteristics of the 160 MLC are capable of improving the quality of dose delivery with respect to precision and dose conformity.

摘要

新的技术发展一直致力于改善放射治疗的效果。通过使用计算机控制的多叶准直器（MLC），治疗质量和患者 throughput 的效率显著提高。新的 MLC 设计旨在进一步增强这些优势。在本文中，我们展示了对西门子医疗解决方案公司新型 160 MLC 的首次详细实验研究。评估包括对典型 MLC 特性的实验研究，如泄漏、舌槽效应、半值层、叶片速度以及使用 6 MV 治疗束时的叶片定位精度。由于采用了叶片轻微倾斜而非常见舌槽设计的新设计原则，泄漏率极低，平均为 0.37%。但由于倾斜，出现了三角形舌槽效应。其幅度约为 19%，与采用常见舌槽设计的 MLC 所测量的剂量缺陷相似。对于标准的 100×100 mm² 射野，在深度 d(max)=15 mm 处测量的平均纵向半值层，中心区域为 4.1±0.5 mm，对于 400×400 mm² 的整个射野范围则增加到 4.9±1.3 mm。这种增加部分归因于单聚焦设计以及 MLC 与等中心之间的大距离，从而实现了较大的患者间隙。关于叶片速度，进行了不同的速度测试。使用千伏成像面板连续记录移动叶片的位置。测量的最大叶片速度为 42.9±0.6 mm/s。此外，还进行了几种典型的调强放射治疗，并将其与西门子 OPTIFOCUS MLC 的输送时间进行了比较。观察到输送时间平均减少了 11%。本文给出的实验结果表明，160 MLC 的剂量学特性在精度和剂量适形性方面能够提高剂量输送的质量。