• Radiation Oncology Journal
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• v.19 no.3
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• pp.275-286
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• 2001

Purpose : To setup procedures of quality assurance (OA) for implementing intensity modulated radiation therapy (IMRT) clinically, report OA procedures peformed for one patient with prostate cancer. Materials and methods : $P^3IMRT$ (ADAC) and linear accelerator (Siemens) with multileaf collimator are used to implement IMRT. At first, the positional accuracy, reproducibility of MLC, and leaf transmission factor were evaluated. RTP commissioning was peformed again to consider small field effect. After RTP recommissioning, a test plan of a C-shaped PTV was made using 9 intensity modulated beams, and the calculated isocenter dose was compared with the measured one in solid water phantom. As a patient-specific IMRT QA, one patient with prostate cancer was planned using 6 beams of total 74 segmented fields. The same beams were used to recalculate dose in a solid water phantom. Dose of these beams were measured with a 0.015 cc micro-ionization chamber, a diode detector, films, and an array detector and compared with calculated one. Results : The positioning accuracy of MLC was about 1 mm, and the reproducibility was around 0.5 mm. For leaf transmission factor for 10 MV photon beams, interleaf leakage was measured $1.9\%$ and midleaf leakage $0.9\%$ relative to $10\times\;cm^2$ open filed. Penumbra measured with film, diode detector, microionization chamber, and conventional 0.125 cc chamber showed that $80\~20\%$ penumbra width measured with a 0.125 cc chamber was 2 mm larger than that of film, which means a 0.125 cc ionization chamber was unacceptable for measuring small field such like 0.5 cm beamlet. After RTP recommissioning, the discrepancy between the measured and calculated dose profile for a small field of $1\times1\;cm^2$ size was less than $2\%$. The isocenter dose of the test plan of C-shaped PTV was measured two times with micro-ionization chamber in solid phantom showed that the errors upto $12\%$ for individual beam, but total dose delivered were agreed with the calculated within $2\%$. The transverse dose distribution measured with EC-L film was agreed with the calculated one in general. The isocenter dose for the patient measured in solid phantom was agreed within $1.5\%$. On-axis dose profiles of each individual beam at the position of the central leaf measured with film and array detector were found that at out-of-the-field region, the calculated dose underestimates about $2\%$, at inside-the-field the measured one was agreed within $3\%$, except some position. Conclusion : It is necessary more tight quality control of MLC for IMRT relative to conventional large field treatment and to develop QA procedures to check intensity pattern more efficiently. At the conclusion, we did setup an appropriate QA procedures for IMRT by a series of verifications including the measurement of absolute dose at the isocenter with a micro-ionization chamber, film dosimetry for verifying intensity pattern, and another measurement with an array detector for comparing off-axis dose profile.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.31 no.3
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• pp.54-60
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• 2013

This study carried out a phytosociological research by Z.-M. school's method describing vegetation structure and management solution about nutmeg tree's(Torreya nucifera ) forests. The nutmeg tree's forests have developed intervale and hills in warm-temperate evergreen broad-leaved forests zone. The nutmeg tree's forests composed 50 familly, 80 genus, 88 species divided two syntaxa(typical sub-community, Arachniodes aristata sub-community) by species composition and correspond to habitat condition. The nutmeg tree's forests show a uniform forest's structure which composed 3~4 layer of sub-tree and shrub. And it was worthy of special mention which characterized diagnostic species of Camellietea japonicae in the warm-temperate evergreen broad-leaved forests. In case of forests floor, were a high rate in order of Ophiopogon japonicus, Polystichum tripteron, Arisaema ringens. And Oplismenus undulatifolius which represent mantle communities as well. This indicates that the nutmeg tree's forests are exposed by humman effects sustainedly. The nutmeg tree's young trees appeared a high rate at half shade and shade. The vigorous tree species have to spacing cutting instead of the heavy thinning that consist in with a shout of declining astructur and function of the forest ecosystem for maintaining a nutmeg tree's forests. And we suggest for the density regulation of the sub-tree and shrub. In conclusion, need to the continuous monitoring about the vegetation structure and management solution for the sustainable nutmeg tree's forests.