Proceedings of the Korean Society of Medical Physics Conference (한국의학물리학회:학술대회논문집)

Korean Society of Medical Physics (한국의학물리학회)
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Practical Virtual Compensator Design with Dynamic Multi-Leaf Collimator(dMLC) from Iso-Dose Distribution

  • Song, Ju-Young (Dept. of Biomedical Engineering, College of Medicine, The Catholic University of Korea) ;
  • Suh, Tae-Suk (Dept. of Biomedical Engineering, College of Medicine, The Catholic University of Korea) ;
  • Lee, Hyung-Koo (Dept. of Biomedical Engineering, College of Medicine, The Catholic University of Korea) ;
  • Choe, Bo-Young (Dept. of Biomedical Engineering, College of Medicine, The Catholic University of Korea) ;
  • Ahn, Seung-Do (Dept. of Radiation Oncology, Asan Medical Center, College of Medicine, University) ;
  • Park, Eun-Kyung (Dept. of Radiation Oncology, Asan Medical Center, College of Medicine, University) ;
  • Kim, Jong-Hoon (Dept. of Radiation Oncology, Asan Medical Center, College of Medicine, University) ;
  • Lee, Sang-Wook (Dept. of Radiation Oncology, Asan Medical Center, College of Medicine, University) ;
  • Yi, Byong-Yong (Dept. of Radiation Oncology, Asan Medical Center, College of Medicine, University)
  • Published : 2002.09.01
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Abstract

The practical virtual compensator, which uses a dynamic multi-leaf collimator (dMLC) and three-dimensional radiation therapy planning (3D RTP) system, was designed. And the feasibility study of the virtual compensator was done to verify that the virtual compensator acts a role as the replacement of the physical compensator. Design procedure consists of three steps. The first step is to generate the isodose distributions from the 3D RTP system (Render Plan, Elekta). Then isodose line pattern was used as the compensator pattern. Pre-determined compensating ratio was applied to generate the fluence map for the compensator design. The second step is to generate the leaf sequence file with Ma's algorithm in the respect of optimum MU-efficiency. All the procedure was done with home-made software. The last step is the QA procedure which performs the comparison of the dose distributions which are produced from the irradiation with the virtual compensator and from the calculation by 3D RTP. In this study, a phantom was fabricated for the verification of properness of the designed compensator. It is consisted of the styrofoam part which mimics irregular shaped contour or the missing tissues and the mini water phantom. Inhomogeneous dose distribution due to the styrofoam missing tissue could be calculated with the RTP system. The film dosimetry in the phantom with and without the compensator showed significant improvement of the dose distributions. The virtual compensator designed in this study was proved to be a replacement of the physical compensator in the practical point of view.

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