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손기홍,조승룡,김진성,한영이,주상규,안성환,신은혁,신정석,박원,표홍렬,최두호,Son, Kihong,Cho, Seungryong,Kim, Jin Sung,Han, Youngyih,Ju, Sang Gyu,Ahn, Sung Hwan,Shin, Eunhyuk,Shin, Jung Suk,Park, Won,Pyo, Hongryul,Choi, Doo Ho Korean Society of Medical Physics 2013 의학물리 Vol.24 No.3
본 연구는 총 10명의 전립선 암 환자를 대상으로 세기조절방사선치료(IMRT), 균일스캐닝양성자치료(USPT), 그리고 세기조절양성자치료(IMPT)기술을 이용한 치료계획의 결과를 비교, 평가 하였다. 각 치료 계획은 타깃 체적의 95%에 70 Gy가 28회 분할 조사되도록 하였으며 세기조절방사선치료(IMRT)에서는 step-and-shoot 기법을 이용하여 총 7개의 빔을 사용하여 방사선을 조사하였고, 균일세기양성자치료(USPT)와 세기조절양성자치료(IMPT)에서는 동일한 방사선 가중치의 측방향대향조사면(lateral opposing field)를 사용하여 타깃에 처방선량이 전달되도록 하였다. 한편, 세기조절양성자치료(IMPT)의 최적화를 위해 IMRT치료와 유사한 Inverse planning을 수행하였다. 결과 비교를 위해 타깃의 균질성지수(homogeneity index) 및 동형지수(conformity index)와 정상조직의 정상조직합병증확률(NTCP)을 계산하였다. 비록 치료기법간에 균질성지수(homogeneity index), 동형지수(conformity index)차이가 크지 않았지만, 직장의 경우 각 세기조절방사선치료(IMRT), 균일스캐닝 양성자치료(USPT) 및 세기조절양성자치료(IMPT)에서 2.233, 3.326 및 1.707로 계산되었다. 또한 방광의 정상조직합병증확률(NTCP)는 0.008, 0.003, 및 0.002를 나타내었다. 직장과 방광의 NTCP 값이 IMPT을 사용할 때 유의하게 낮은 값을 보이는 것을 확인하였다. 본 연구를 통해 전립선 암의 방사선 치료 시 세기조절방사선치료(IMRT)보다 양성자를 이용한 방사선 치료, 특히 최적화된 세기조절양성자치료(IMPT)가 치료 효과를 높일 수 있는 치료계획이 될 수 있음을 확인할 수 있었다. This study assessed compared photon and proton treatment techniques, such as intensity modulated radiation therapy (IMRT), uniform scanning proton therapy (USPT), and intensity modulated proton therapy (IMPT), for a total of 10 prostate cancers. All treatment plans delivered 70 Gy to 95% of the planned target volume in 28 fractions. IMRT plans had 7 fields for the step and shoot technique, while USPT and IMPT plans employed two equally weighted, parallel-opposed lateral fields to deliver the prescribed dose to the planned target. Inverse planning was then incorporated to optimize IMPT. The homogeneity index (HI) and conformity index (CI) for the target and the normal tissue complication probability (NTCP) for organ at risk (OAR) were calculated. Although the mean HI and CI for target were not significantly different for each treatment techniques, the NTCP of the rectum was 2.233, 3.326, and 1.707 for IMRT, USPT, and IMPT, respectively. The NTCP of the bladder was 0.008, 0.003, and 0.002 respectively. The NTCP values at the rectum and bladder were significantly lower using IMPT. Our study shows that using proton therapy, particularly IMPT, to treat prostate cancer could be beneficial compared to 7-field IMRT with similar target coverage. Given these results, radiotherapy using protons, particularly optimized IMPT, is a worthwhile treatment option for prostate cancer.
Sparse-view Image Reconstruction in Prospectively Gated Micro-CT for Fast and Low-dose Imaging
민종환,조규성,조승룡,Kyoungwoo Kim 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.7
We conducted a feasibility study using a total-variation minimization algorithm for image reconstruction in prospectively gated micro computed tomography (micro-CT). The total-variation (TV) minimization algorithm exploits the sparseness of the image’s gradient magnitude and can successfully reconstruct CT images from undersampled data for which conventional analytic reconstruction algorithms fail. We implemented the algorithm and applied it to sparsely-sampled data for a mouse by using a prospectively gated micro-CT system. The images were successfully reconstructed, and an image similarity index was quantitatively calculated with respect to the reference images reconstructed from fully-sampled data. Compared to a conventional image reconstruction algorithm, the TV-minimization algorithm substantially reduced image inaccuracy related to the image artifacts.
THE ADAPTATION METHOD IN THE MONTE CARLO SIMULATION FOR COMPUTED TOMOGRAPHY
이형건,윤창연,조승룡,박성호,이원호 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.4
The patient dose incurred from diagnostic procedures during advanced radiotherapy hasbecome an important issue. Many researchers in medical physics are using computationalsimulations to calculate complex parameters in experiments. However, extendedcomputation times make it difficult for personal computers to run the conventional MonteCarlo method to simulate radiological images with high-flux photons such as imagesproduced by computed tomography (CT). To minimize the computation time withoutdegrading imaging quality, we applied a deterministic adaptation to the Monte Carlocalculation and verified its effectiveness by simulating CT image reconstruction for animage evaluation phantom (Catphan; Phantom Laboratory, New York NY, USA) and ahuman-like voxel phantom (KTMAN-2) (Los Alamos National Laboratory, Los Alamos, NM,USA). For the deterministic adaptation, the relationship between iteration numbers andthe simulations was estimated and the option to simulate scattered radiation was evaluated. The processing times of simulations using the adaptive method were at least 500times faster than those using a conventional statistical process. In addition, compared withthe conventional statistical method, the adaptive method provided images that were moresimilar to the experimental images, which proved that the adaptive method was highlyeffective for a simulation that requires a large number of iterationsdassuming no radiationscattering in the vicinity of detectors minimized artifacts in the reconstructed image.