Department of Technology of Radiology and Radiotherapy, Allied Medical Science School, Tehran University of Medical Science, Tehran, Iran.
Phys Med. 2013 Jun;29(4):350-6. doi: 10.1016/j.ejmp.2012.05.001. Epub 2012 May 31.
In this work dosimetric parameters of two multi-leaf collimator (MLC) systems, namely the beam modulator (BM), which is the MLC commercial name for Elekta "Synergy S" linear accelerator and Radionics micro-MLC (MMLC), are compared using measurements and Monte Carlo simulations. Dosimetric parameters, such as percentage depth doses (PDDs), in-plane and cross-plane dose profiles, and penumbras for different depths and field sizes of the 6 MV photon beams were measured using ionization chamber and a water tank. The collimator leakages were measured using radiographic films. MMLC and BM were modeled using the EGSnrc-based BEAMnrc Monte Carlo code and above dosimetric parameters were calculated. The energy fluence spectra for the two MLCs were also determined using the BEAMnrc and BEAMDP. Dosimetric parameters of the two MLCs were similar, except for penumbras. Leaf-side and leaf-end 80-20% dose penumbras at 10 cm depth for a 10×10 cm(2) field size were 4.8 and 5.1mm for MMLC and 5.3 mm and 6.3 mm for BM, respectively. Both Radionics MMLC and Elekta BM can be used effectively based on their dosimetric characteristics for stereotactic radiosurgery and radiotherapy, although the former showed slightly sharper dose penumbra especially in the leaf-end direction.
在这项工作中，使用测量和蒙特卡罗模拟比较了两种多叶准直器（MLC）系统的剂量学参数，即射束调制器（BM）和 Radionics 微多叶准直器（MMLC）。使用电离室和水箱测量了 6MV 光子束不同深度和射野大小的百分深度剂量（PDD）、平面内和平面外剂量分布以及半影。使用射线照相胶片测量了准直器泄漏。使用 EGSnrc 为基础的 BEAMnrc 蒙特卡罗代码对 MMLC 和 BM 进行建模，并计算了上述剂量学参数。还使用 BEAMnrc 和 BEAMDP 确定了两种 MLC 的能谱。两种 MLC 的剂量学参数相似，除了半影。在 10cm 深度和 10×10cm2 射野大小下，对于 80-20%剂量半影，MMLC 的叶片侧和叶片端为 4.8mm 和 5.1mm，而 BM 为 5.3mm 和 6.3mm。尽管前者在叶片端方向的剂量半影稍微更锐利，但基于其立体定向放射外科和放射治疗的剂量学特性，Radionics MMLC 和 Elekta BM 均可有效使用。
