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민철희,김찬형,Jang Guen Park 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3
Recently a prototype prompt gamma scanner system, named the PGS (prompt gamma scanner), was constructed and used to demonstrate that there is a clear correlation between prompt gamma distribution and the range of the proton beam in a patient. However, the PGS system requires a scanning process to obtain the prompt gamma distribution; consequently, it cannot be used in ``spot scanning'', in which the proton beam is continuously moving during treatment. The present Monte Carlo study explored the feasibility of a new detection system that does not require a scanning process, that is, that uses a linear array of scintillation detectors and photodiodes for online measurement of the proton beam range. The simulation results are very encouraging, showing that an array-type prompt gamma detection system can measure the proton beam range despite the fact that, with this system, the level of background gammas somewhat increases as a result of reduced collimator shielding. This paper discusses those simulation results, as well as some important design considerations based on them.
민철희,조성구,Han Rim Lee,Yeon Su Yeom,김찬형 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.61
The close relationship between the proton dose distribution and the distribution of prompt gammas generated by proton-induced nuclear interactions along the path of protons in a water phantom was demonstrated by means of both Monte Carlo simulations and limited experiments. In order to test the clinical applicability of the method for determining the distal dose edge in a human body, a human voxel model, constructed based on a body-composition-approximated physical phantom, was used, after which the MCNPX code was used to analyze the energy spectra and the prompt gamma yields from the major elements composing the human voxel model; finally, the prompt gamma distribution, generated from the voxel model and measured by using an array-type prompt gamma detection system, was calculated and compared with the proton dose distribution. According to the results, effective prompt gammas were produced mainly by oxygen, and the specific energy of the prompt gammas, allowing for selective measurement, was found to be 4.44 MeV. The results also show that the distal dose edge in the human phantom, despite the heterogeneous composition and the complicated shape, can be determined by measuring the prompt gamma distribution with an array-type detection system.
통계적 공정관리 추진시 측정시스템 평가의 실시방법에 관한 연구
민철희,백재욱 한국통계학회 1998 응용통계연구 Vol.11 No.1
품질향상을 위한 통계적 공정관리 추진시 데이터의 신뢰성 확보는 무엇보다 중요하다. 그런데 측정치는 계측기 뿐만 아니라 측정자, 측정방법, 측정재료 등 보다 많은 요인들에 의해 영향을 받는다. 본 논문에서는 고전적인 측정시스템 평가에서 주로 관리하는 정확도, 정밀도 및 안정도를 실제 데이터를 이용하여 어떻게 평가하는지 알아보기로 한다. Corrent measurement system assessment is crucial in helping improve process or quality. In this article, we would like to apply several methods of measurement system assessment in statistical process control. Specifically, focus is on accuracy, precision (both repeatability and reproducibility included), and stability of the measurement process.