Akula Roopa Rani, Ayyangar Komanduri, Reddy Alla Ramalinga, Kumar Ayyalasomayajula Anil, Yadagiri Reddy Pal Reddy
MSc, Department of Physics, Osmania University, Hyderabad, India.
MSc, Department of Radiation Oncology, MNJ Institute of Oncology & Regional Cancer Center, Hyderabad, India.
J Biomed Phys Eng. 2021 Dec 1;11(6):723-734. doi: 10.31661/jbpe.v0i0.2002-1073. eCollection 2021 Dec.
In developing countries like India, cobalt-60 machines still find their applicability, considering the cost and maintenance issues. With a view to deliver conformal treatment plans using teletherapy machines, an automated Multi-Leaf Collimator (MLC) was developed for the existing machines as a retrofit attachment to the collimator assembly without any modifications to the unit.
This study aims to investigate the radiation characteristics of leaf designs incorporated in two add-on prototype MLC systems with respect to the shape of leaf projected at the isocenter plane and the isodose distribution around the target. Besides, the dosimetric characteristics of prototype MLC with divergent leaf design are validated through simulation and experimental measurements.
In this experimental study, two add-on prototype MLC systems were designed and fabricated. The characteristic measurements of leaf designs incorporated in both the prototypes were carried out using Gafchromic films (GAF) and compared with Monte Carlo (MC) simulations. For divergent leaf design, beam profiles were obtained using Monte Carlo simulations which are complemented with the results obtained from measurements of radiochromic films and ionization chamber (IC) profiler. Dosimetric characteristics like radiation field width and beam penumbra were evaluated.
The Monte Carlo simulated data are in agreement with experimental data from IC profiler as well as from Radiochromic films. The results of this study are well within acceptable tolerance limits.
The prototype MLC system designed for existing telecobalt machines supports its clinical applicability for conformal therapy to better manage treatment in rural areas, which can provide superior cost effective treatments.
在印度这样的发展中国家，考虑到成本和维护问题，钴-60机器仍有其适用性。为了使用远距离治疗机器提供适形治疗计划，开发了一种自动多叶准直器（MLC），作为现有机器的改造附件安装在准直器组件上，而无需对设备进行任何修改。
本研究旨在研究两种附加原型MLC系统中叶片设计的辐射特性，包括在等中心平面上投影的叶片形状以及靶区周围的等剂量分布。此外，通过模拟和实验测量验证了具有发散叶片设计的原型MLC的剂量学特性。
在本实验研究中，设计并制造了两种附加原型MLC系统。使用Gafchromic胶片（GAF）对两种原型中包含的叶片设计进行特性测量，并与蒙特卡罗（MC）模拟结果进行比较。对于发散叶片设计，使用蒙特卡罗模拟获得射野轮廓，并辅以放射性色胶片和电离室（IC）轮廓仪测量结果。评估了辐射野宽度和射束半值层等剂量学特性。
蒙特卡罗模拟数据与IC轮廓仪以及放射性色胶片的实验数据一致。本研究结果在可接受的公差范围内。
为现有的钴远距离治疗机设计的原型MLC系统支持其在适形治疗中的临床适用性，以便更好地管理农村地区的治疗，从而提供更具成本效益的优质治疗。
