Ulin K, Palisca M
Department of Radiation Oncology, New England Medical Center, Boston, MA 02111, USA.
Int J Radiat Oncol Biol Phys. 1996 Jul 1;35(4):785-92. doi: 10.1016/0360-3016(96)00153-8.
This study was undertaken to show that scattering foils could be used as electron beam compensators.
Two scattering foils were designed to improve the dose homogeneity when a curved surface is irradiated with electrons. One scattering foil, constructed of mylar, was designed for use with a single 6 MeV electron field. The second scattering foil, constructed of lead, was designed to homogenize the dose along the matchline of two abutting electron fields. Measurements with the second compensator were made at energies of 6, 9, and 12 MeV. The compensators were mounted over the topmost opening of the electron cone. A simple method for modeling the effect of the second compensator using a conventional treatment planning system was also evaluated.
When the mylar compensator was placed atop the 25 x 25 cm cone and a Rando phantom irradiated with 6 MeV electrons, the dose at the field edges was increased by about 10%. Use of the lead foil compensator for two abutting fields gave a highly uniform dose along the matchline, without perturbing the isodoses at depth or at the other field edges. Measured hot spots in the Rando phantom for 6 and 9 MeV electrons were 104 and 108%, respectively. The effect of the lead foil compensator was successfully modeled on a conventional treatment planning system by summing beams of different field sizes.
Both compensators were effective in improving the dose homogeneity within the target volume.
本研究旨在表明散射箔可作为电子束补偿器使用。
设计了两种散射箔，用于在曲面接受电子照射时改善剂量均匀性。一种由聚酯薄膜制成的散射箔，设计用于单个6兆电子伏电子野。第二种由铅制成的散射箔，旨在使两个相邻电子野的匹配线上的剂量均匀化。在6、9和12兆电子伏的能量下对第二种补偿器进行了测量。补偿器安装在电子射野挡铅的最上方开口处。还评估了一种使用传统治疗计划系统对第二种补偿器效果进行建模的简单方法。
当将聚酯薄膜补偿器置于25×25厘米射野挡铅顶部并用6兆电子伏电子照射兰多体模时，射野边缘的剂量增加了约10%。对两个相邻野使用铅箔补偿器可使匹配线上的剂量高度均匀，而不会干扰深度处或其他射野边缘的等剂量线。在兰多体模中，6兆电子伏和9兆电子伏电子的测量热点分别为104%和108%。通过对不同野大小的射束求和，成功地在传统治疗计划系统上对铅箔补偿器的效果进行了建模。
两种补偿器均能有效改善靶区内的剂量均匀性。
