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Poly(lactic acid) (PLA) was hybridised with epoxide-functionalised silane (GTMS) through reactive extrusion. The GTMS was grafted successfully to PLA via a ring-opening reaction with the nucleophilic end groups of PLA. For hybridisation, PLA was extruded with various amounts of GTMS between 0 and 2.0 phr at 200 °C. The PLA hybrids were characterised by Fourier transform infrared spectroscopy and scanning electron microscopy. Their properties were examined by tensile testing, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, and rheological characterisation. The glass transition temperature of the hybrids decreased to 52.7 °C compared to that of PLA (60.1 °C). The toughness was enhanced significantly by approximately 380% with only a 0.5 phr loading of GTMS. The hydrolytic degradation was also delayed by the hybridised GTMS in the PLA matrix. In conclusion, hybridisation by GTMS influenced the thermal, mechanical and degradable properties of the PLA hybrids substantially.

The distribution of plant communities in the salt marshes of the southwestern coasts of South Korea was studied, along with environmental or plant factors, by canonical correspondence analysis (CCA) and the competitor (C), stress tolerator (S), and ruderal (R) (CSR) ecological strategies. The coastal salt-marsh plants were classified into three plant-factor groups in the CCA biplot diagram. Group 1 was correlated with LS and FP. Group 2 was correlated with CH and SLA, and Group 3 was correlated with LA, LDMC and LDW. The salt-marsh plants were classified into four soil-factor groups in the CCA biplot diagram. First, the group factor was correlated with TN, TOC, and Ca2+. Second, the group factor was distributed according to Mg2+, soil texture as Clay and Silt. Third, the group factor was distributed according to Salinity and Na+ content. Fourth, the group factor was distributed according to Sand content. To clarify the relative significance of competition, stress, and disturbance in the distribution process of plant communities, the CSR distribution model was adopted. The nine species showed CR (competitor-ruderal) strategies: Artemisia fukudo, Artemisia scoparis, Aster tripolium, Atriplex gmelinii, Imperata cylindrica var. koenigii, Salicornia europaea, Suaeda japonica, and Suaeda maritima. The four species with C (competitor) strategies were Artemisia capillaris, Limonium tetragonum, Triglochin maritimum, and Zoysia sinica. Carex scabrifolia and Phragmites communis displayed SC (stress-tolerant-competitor). Both distribution patterns of the CCA diagrams and CSR triangles may provide a useful scientific basis for protecting and restoring salt marshes and their valuable ecosystem services, considering the increasing disturbances.

The internal control system is an essential process to maintain and manage an organization. It helps an organization achieve its goal by containing risks that might affect its accomplishment of the goal. The system is considered increasingly important as it is a fundamental procedure to protect a company’s asset by detecting and preventing irregularities and malpractices. This research compares and analyzes laws and regulations pertaining to internal control systems in the U.S., Japan, and Korea and their key elements. The research result is as described below. The U.S. was the first country to establish laws and regulations on corporate internal controls in order to improve its law enforcement and public disclosure guidelines. The U.S. Securities and Exchange Commission (“SEC”) played a leading role in establishing the Foreign Corrupt Practices Act (“FCPA”) to prevent accounting irregularities of the U.S. companies. The Model Business Corporation Act (“MBCA”) provides basic guidelines of internal controls and stipulates that the board of directors meeting shall be responsible for building and operating the internal control system. Moreover, the Act practically enforces practical control over companies in the U.S. by stipulating compulsory internal control (including com- pliance issues) in the listed company manuals of the stock exchange. After that, Sarbanes-Oxley Act (“the SOX Act”) was established to have management and external auditors responsible for internal control in a stronger and stricter manner. The SOX Act provides regulations on accounting, corporate governance, and audit, encompassing all three areas of internal control covered in Committee of Sponsoring Organizations of the Treadway Commission (“COSO”) report. Japan introduced regulations on establishment of the internal control system in its Corporate Act of 2005. Afterwards, due to the unlawful acts of Japanese companies, articles and provisions concerning internal control system were stipulated in the Financial Instruments and Exchange Act (“FIEA”). In particular, establishment of the internal control systems is a legal requirement in Japan’s Corporate Act. According to the Act, every large company in the country shall establish an internal control system and issue a public disclosure on the operational result of the system. Where the operation is considered inappropriate, the system shall face an audit. Japan’s Corporate Act categorizes companies in three major groups; companies with board of directors meeting, those without the board, and other companies with committees. It is to specify the responsibility of directors for internal control. The enforcement decree of the Corporation Act specifies matters concerning the compliance management system, for instance directors’ performance of duty shall be in compliance with laws, regulations, and the articles of incorporation. Moreover, FIEA regulates internal control only in terms of corporate accounting, such as reliability of financial reporting. Hence, the definition of internal control suggested by the Corporation Act and FIFA is different from each other and the discrepancy has led to some controversies. Japan reckons internal control as an integrated framework, similar to as suggested by the COSO report of the U.S. issued in 1992. In line with the context of the COSO report, Japan is trying to reflect circumstances of local companies in its legal system. As such, there are some differences in the relevant laws of the U.S. and Japan. The SOX Act of the U.S. largely focuses on financial reporting in regard of internal control, while internal control function is dependent on the monitoring of the board of directors. However, Japan’s Corporate Act mandates large companies and companies with committees to make financial reports on their internal control system as well as ensures the companies lawfully and efficiently perform their business. Korea has broader regulations about internal control in finance related laws including the Financial Investment Services and Capital Markets Act and the Act on External Audit of Stock Companies. Finance related laws already have articles about internal control standards and compliance officer system. But it was only April 2011 that the Commercial Act of Korea stipulated compliance control standards and compliance officer system. Hence the Act includes only compliance control standards, not internal control standards for companies. To establish the internal control system, a clear definition on internal control organizations shall be established to ensure independence of their status and duties. In addition, an effective internal control system has to be installed, including internal control criteria. At the same time, the management of companies and financial institutions should have strong commitment to actively establish and operate the internal control system. This research limits its study scope to comparison and analysis of internal control related regulations and key factors in the U.S., Japan, and Korea and suggests indications from the analysis result. A following research will provide an empirical study based on the result of this research.

Poly(lactic acid) (PLA) has been highlighted for its excellent biodegradability and hydro-degradability. On the other hand, an estimation of the biodegradability of PLA generally requires lengthy measurements over several months because it is difficult for the terminal decomposer, a microorganism, to uptake and utilize the polymer material, making it difficult to analyze and compare the results quantitatively. In this study, it was hypothesized that the inclusion of mono lactic acid (LA) in a PLA blend improves the level of microbial attachment to the surface of the PLA blend, and increases the biodegradation rate. PLA blend films containing 1%, 2.5%, and 5% of LA were prepared, and their morphological changes to the surface and cross section of films were investigated. The biodegradation of a PLA/LA blend using digester sludge was estimated quantitatively from the specific gas production rate (SGPR) based on the surface area of the blend film. The physical and chemical properties before and after biodegradation were also compared. These results show that PLA/LA blends with a controlled degradation rate can be developed by incorporating readily degradable chemicals, and implemented as environmentally friendly plastics and polymers.

Biodegradable polymers and plastics have been investigated extensively and commercial applications of poly(lactic acid) (PLA) are being implemented. A feasible and rapid estimation of the biodegradability is urgently needed to satisfy environmental regulations and consumer’s desire considering the market situation. On the other hand, an estimation of the biodegradability of polymers normally requires a long time for measurement and there is less standardization, making it difficult to analyze and compare. This study examined the microbial degradation of PLA with anaerobic digester sludge. The gas production and by-product formation from PLA degradation were analyzed to assess the extent of biodegradation. The different specific surface areas of the PLA granules results in different gas production rates and degradation capacities, while an increase in surface area tends to increase the level of gas production. The specific CO2 and CH4 production rates were estimated based on the total surface area to quantify the biodegradability of PLA. The results showed that a rapid and feasible testing method of biodegradability is possible, and can be implemented to develop and optimize environmentally friendly plastics and polymers.

Lee, J.-S.; Son, D.-H.; Lee, S.-H.; Myeong, H.-H.; Cho, J.-S.; Lee, J.-C.; Lee, J.-Y.; Park, C.-S., and Kim, J.-W., 2020. Canonical correspondence analysis ordinations and competitor, stress tolerator, and ruderal strategies of coastal dune plants in South Korea. Journal of Coastal Research, 36(3), 528–535. Coconut Creek (Florida), ISSN 0749-0208.The distribution of plant communities in the sand dunes of the SW coasts of South Korea was studied, along with environmental factors and plant traits, by canonical correspondence analysis (CCA). The competitor, stress tolerator, and ruderal (CSR) ecological strategies were also evaluated. The coastal sand dune plants were classified into two plant trait groups in the CCA biplot diagram. First, vegetation was correlated with leaf dry weight, canopy height, specific leaf area, leaf dry matter content, and lateral spread. Second, it was correlated with the flowering period and flowering start. Coastal sand dune plants were classified into three soil factor groups in axes 1 and 2 of the CCA biplot diagram. First, the vegetation was correlated with total nitrogen (T-N), K+, Silt, Mg2+, Na+, and clay contents. Second, it was correlated with Ca2+. Third, it was correlated with the sand contents. To elucidate the relative significance of competition, stress, and disturbance in the distribution process of plant communities, the CSR distribution model was adopted. Many coastal plants (12 species) showed competitor-ruderal/competitor-stress-tolerant-ruderal strategies: Artemisia fukudo, Atriplex gmelinii, Carex kobomugi, Calystegia soldanella, Digitaria ciliaris, Linaria japonica, Messerschmidia sibirica, Oenothera bieenis, Salicornia europaea, Salsola komarovii, Suaeda glauca, and Suaeda maritima. The four species with stress-tolerant-competitor/competitor-stress-tolerant-ruderal strategies were Carex pumila, Imperata cylindrica var. koenigii, Limonium tetragonum, and Zoysia sinica. Conyza canadensis, Ischaemum anthephoroides, Phragmites communis, and Vitex rotundifolia displayed competitor/stress-tolerant-competitor, competitor-ruderal, stress-tolerant-competitor, and C/SC strategies, respectively. The differences in distribution and restoration patterns of the CCA diagrams and CSR triangles may be attributable to different adaptions of plant traits or soil factors.

In this paper, we propose a internal antenna for wirless HDMI dongle device using the folded monopole structure. The proposed antenna is for 2.4GHz and 5.8GHz. The antenna optimized for parameters length, gap, width, and radius of semicircular of monopole antenna using the `F` structure. To confirm the characteristics of the antenna parameters, HFSS from ANSYS Inc. was used for the analysis. We used an FR4 dielectric substrate with a dielectric constant of 4.4. The HDMI dongle size of the proposed antenna is , and the size of the antenna area is . There is a value of return loss less then -10dB in 2.4GHz and 5.8GHz, band and the maximum antenna gain is -4.13dBi. The result proved the possibility of the practical using `F` structure that came frin comparing and analyzing the measured and simulated data of the antenna.

The purpose of this study is to evaluate the clinical usefulness of modulated arc (mARC) treatment techniques. The mARC treatment plans of the non-small cell lung cancer (NSCLC) patients were performed in order to verify the clinical usefulness of mARC. A pre study was conducted to find the most competent plan condition of mARC treatment and the usefulness of mARC treatment plan was evaluated by comparing it with the other Arc treatment plans such as Tomotherapy and RapidArc. In the case of mARC, the optimal condition for the mARC plan was determined by comparing the dosimetric performance of the mARC plans with the use of various parameters. The various parameters includes the photon energies (6 MV, 10 MV), optimization point angle (6{\deg}-10{\deg} intervals), and total segment number (36-59 segment). The best dosimetric performance of mARC was observed at 10 MV photon energy and the point angle 6 degree, and 59 segments. The each treatment plans of three different techniques were compared with the following parameters: conformity index (CI), homogeneity index (HI), target coverage, dose in the OARs, monitor units (MU), beam on time and the normal tissue complication probability (NTCP). As a result, all three different treatment techniques show the similar target coverage. The mARC results the lowest V20 and MU per fraction compared with both RapidArc and Tomotherapy plan. The mARC plan reduces the beam on time as well. Therefore, the results of this study provided a satisfactory result which mARC technique is considered as a useful clinical technique for radiation treatment., Comment: 11 pages, 4 figures

ZnO 1- x Se x films with various selenium concentrations are deposited on the sapphire substrate (0 0 0 1) by pulsed laser deposition technique. Structural properties of the thin films studied by X-ray diffraction (XRD) and chemical bonding studied by X-ray photoelectron spectroscopy (XPS) reveals that Se is substituted in O site during the growth of ZnO 1- x Se x films. Optical properties are analyzed by UV–Visible spectrometer. From the plot for ( αhυ ) 2 vs photon energy, it is inferred that the band gap energy of ZnO 1- x Se x gradually reduces to 2.85 eV with increasing Se concentration.

ZnO:Cl thin films grown on glass substrates at 200 °C by the pulsed laser deposition (PLD) technique using ZnO:Cl targets show preferential c-axis (0002) orientation having hexagonal wurtzite structure without secondary phases. The chlorine concentration in the ZnO:Cl thin films is varied from 1.04 to 7.28 at%. X-ray photoelectron spectroscopy (XPS) studies indicate existence of ZnO and ZnCl bonding. Hall effect measurements and UV–Visible absorption spectra show lowest resistivity of 6.12 × 10−4 Ω cm and average transmittance of 92% in the visible range for the 4.16 at% chlorine-doped ZnO thin film. Possible application of the material as a new transparent conductive zinc oxide is very much imminent in optoelectronic devices.

Chlorine (Cl) doped ZnO thin films are grown using Pulsed Laser Deposition (PLD) to conduct a feasibility study for the possible application of this material as transparent conducting electrode (TCO) in transparent electrodes. Cl doped ZnO films are deposited on c-plane (0001) sapphire (Al2O3) and glass substrates at 100 °C using two Cl doped ZnO targets with chlorine concentrations 1.4 at% and 2.4 at% respectively. Optical properties studied using UV–visible spectrometer indicates that Cl doped ZnO samples have 90% average transmittance in the visible region. A carrier concentration of-4.04 × 1020 cm−3, resistivity of 6.344 × 10−4 Ω cm and sheet resistance of 34.3 Ω/sq at room temperature are derived from Hall measurements and four probe measurements carried out on ZnO:Cl (2.4 at%) thin films. The reports indicate a better transparency and conductance in ZnO compared to similar reports on ZnO published elsewhere. Therefore, Cl doped ZnO is a possible potential TCO alternative for application as transparent electrodes in optoelectronics.

We have developed a computerized system for measuring field electron emission (FE) and field ionization (FI), which has a three-electrode configuration with emitters biased up to 25 kV, and is programmed by the Labview software. The current-voltage curves of nano-tip tungsten and carbon nanotube (CNT) arrays were measured. The electron emission of CNTs proceeded with a turn-on field of 1.24 V/μm and a threshold field of 1.85 V/μm. Compared to the field emission, field ionization turned on at 3.5 V/μm. Raman spectroscopy and scanning electron microscopy (SEM) measurements showed degradation of the CNTs after FE/FI testing. The measurement of a W-tip revealed strong electron emission and instability behavior at a field strength higher than 7.0 V/μm.

This study evaluated the performance of tissue equivalent polymer gel dosimetry as a tool for 3-dimensional dose quality assurance to using Magnetic Resonance Imaging (MRI) measure the dose characteristics of therapeutic radiation using and applying it to intensity modulated radiation therapy (IMRT). The polymer gel under normoxic conditions was synthesized using Gelatin, methyacrylic acid (MAA), hydroquinone (HQ) and tetrakis hydroxymethyl phosphonium chloride (THPC), and a polymer gel dosimeter was fabricated by placing the gel into each phantom appropriate for experimental use. The dose reaction experiment employed Co gamma-rays and a 6-MV photon beam with a dose range of 0 ∼ 14 Gy. The dose characteristics of the polymer gel were compared with those of an ion chamber, Gafchromic EBT2 film, by using MRI. The linear correlations coefficient for the polymer gel, the ion chamber and the film were r = 0.970, r = 0.999, and r = 0.972, respectively. The percentage depth doses at a depth of 50 mm were 85.8% and 84.6% for the polymer gel and the ion chamber, respectively, giving a difference of 1.2%. On the other hand, the percentage depth dose at the depth of 100 mm was 66.2% and 63.7% for the polymer gel and the ion chamber, respectively, indicating a 2.5% gap. The flatness and the symmetry of the gel dosimeter on the cross plane were 3.80% and 3.58%, respectively. The gel dosimeter was applied to an IMRT. The doses measured in the 100% dose domain of the therapeutic plan was 96.2%, 103.0%, and 100% for the axial, sagittal and coronal planes, respectively, highlighting the applicability of the gel dosimeter as a 3-dimensional dosimeter.

The article presents, using Bi doped ZnO, an example of a heavy ion doped oxide semiconductor, highlighting a novel p-symmetry interaction of the electronic states to stabilize ferromagnetism. The study includes both ab initio theory and experiments, which yield clear evidence for above room temperature ferromagnetism. ZnBixO1−x thin films are grown using the pulsed laser deposition technique. The room temperature ferromagnetism finds its origin in the holes introduced by the Bi doping and the p-p coupling between Bi and the host atoms. A sizeable magnetic moment is measured by means of x-ray magnetic circular dichroism at the O K-edge, probing directly the spin polarization of the O(2p) states. This result is in agreement with the theoretical predictions and inductive magnetometry measurements. Ab initio calculations of the electronic and magnetic structure of ZnBixO1−x at various doping levels allow to trace the origin of the ferromagnetic character of this material. It appears, that the spin-orbit energy of the heavy ion Bi stabilizes the ferromagnetic phase. Thus, ZnBixO1−x doped with a heavy non-ferromagnetic element, such as Bi, is a credible example of a candidate material for a new class of compounds for spintronics applications, based on the spin polarization of the p states.

Cu 2 ZnSnS 4 thin films were deposited on corning 7059 glass substrates without substrates heating by rf magnetron sputtering. The Cu/(Zn+Sn) ratio of the thin film sputtered at 75 W was close to the stoichiometry of Cu 2 ZnSnS 4 . However, the S/(Cu+Zn+Sn) ratio was less than the stoichiometry. The as-deposited films were amorphous and annealed in the atmosphere of Ar+S 2 (g). The annealed (1 1 2), (2 0 0), (2 2 0), (3 1 2) planes were conformed to all the reflection of a kesterite structure. A preferred (1 1 2) orientation was observed with the increase of the annealing temperature. The optical absorption coefficient of the thin film was about 1.0×10 4 cm −1 . The optical band energy was derived to be 1.51 eV. The optical absorption coefficient of the sputtered Cu 2 ZnSnS 4 thin films was less than that of CuInS 2 thin film, however, the band gap energy was more appropriate for photovoltaic materials.

To lower the cost of poly(butylene adipate-co-terephthalate) or PBAT, starch was used as a filler in this study. To increase tensile strength of PBAT/starch composites, polymeric methylenediphenyl diisocyanate (pMDI) was used as a compatibilizer. PBAT was melt-mixed with starch in a kneader, and then the mixtures were compression-molded. The effects of starch and pMDI content on the tensile strength and elongation at break of PBAT/starch composites were examined. The morphology and biodegradability of the composites in soil were also studied. The tensile strength of PBAT and PBAT/starch composites increases with increasing content of pMDI. The increase of weight average molecular weight of PBAT and improved interaction between PBAT and starch were observed with increasing content of pMDI. The weight average molecular weights of buried PBAT and the composites in soil significantly decrease. Especially, the reduction of the weight average molecular weight of PBAT/starch (70/30) composite is the most significant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41884.

Water quality impairment from nonpoint source pollution is one of the critical causes of surface water eutrophication in rivers and lakes surrounding agricultural area, Korea. In the Songchon Constructed Wetland (SCW) located in Yeongsan (YS) watershed which has about 1,000 km2 (total watershed area: 3,471 km2) for agricultural area, 19 times of intensive field monitoring in 2010 were conducted with various rainfall patterns and about more 1,000 water samples were measured and analyzed in field and laboratory. To identify the relationship between meteorological conditions and removal efficiency of the constructed wetland, principal component analysis (PCA) and ternary plot analysis was used for 19 field experiment data. Mean treatment performance of TSS, BOD5, COD, TN, and TP was 16.4%, 42.1%, 43.7%, 36.6%, and 57.1%, respectively, as a method of pollutant load reduction for multiple tests of storm events. PCA results revealed that rainfall depth, rainfall intensity, and antecedent dry days (ADDs) can be major components as a representative in each component. Also, ternary contour plots results showed that the treatment performance of SCW in agricultural area during storm events can be affected by three meteorological conditions. These results and phenomena can be applicable to develop the NPS discharge model and to elucidate the relationship between rainfall and storm water runoff using rain radar in a drainage area.

An ion beam system of 20 keV Cockroft-Walton type composed of an AuGe alloy liquid metal ion source is constructed. For the fabrication of ohmic contacts to the n-GaAs, the ion beam extracted from the AuGe alloy source is implanted into the n-GaAs, and current-voltage contact resistivity measurements are carried out to evaluate the quality of the contact. A stable AuGe ion beam (2.5 μA/cm2) is obtained at an extraction voltage of 14.5 kV. The measurements of the contact resistivity are performed by the transmission line model method, and the contact resistivity is 2.4 × 10−5 Ω cm2 for the sample implanted at a dose of 1.9 × 1020/cm3 and annealed at 300 °C for 2 min. The composition-depth profiles measured by Auger electron spectroscopy are compared with the results calculated by Monte Carlo simulation based on two-body collisions. The results of AuGe ion implantation reveal preferential sputtering of As. The Au and Ge depth profiles agree with the results of the Monte Carlo simulation. Zur Herstellung von ohmschen Kontakten an n-GaAs wird ein in einer AuGe-Flussigmetallionenquelle erzeugter Ionenstrahl implantiert. Die Qualitat der Kontakte wird durch Strom-Spannungsmessungen uberpruft. Ein stabiler AuGe-Ionenstrahl (2,5 μA/cm2) wird bei einer Extraktionsspannung von 14,5 kV erhalten. Der mit der Ubertragungsleitungsmethode gemessene Kontaktwiderstand betragt 2,4 × 1020 Ω cm2 fur eine mit 1,9 × 1020/cm3 implantierte und fur 2 min bei 300 °C getemperte Probe. Die Zusammensetzungs-Tiefenprofile werden mittels Augerelektronenspektroskopie gemessen und stimmen mit den Ergebnissen einer auf Zwei-Korperstosen basierenden Monte-Carlo-Simulation gut uberein. Die AuGe-Ionenimplantation fuhrt vorzugsweise zum As-Sputtern.

The absence of a temperature effect in title reactions may signify the violation of classical reactivity-selectivity principle, which has been rationalized in terms of Marcus theory.

72 This work was supported by Kyonggi University Research Grant 2013. Received 30 May 2016, Revised 3 June 2016, Accepted 4 June 2016 Correspondence: Soo-Il Kwon (sikwon@kyonggi.ac.kr) Tel: 82-31-249-9618, Fax: 82-31-253-1165 cc This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Characteristics of CCD Based Optical CT Scanner for Therapeutic Radiation Dosimetry

Summary. Cytotoxic T lymphocytes are essential components of immune responses during chronic hepatitis B (CHB). It has been known that Fas ligand (FasL) and perforin/granzyme B-based mechanisms account for all T cell-mediated cytotoxicity. In the present work, we examined the correlation between injury of the hepatocytes and mRNA expression of FasL and perforin/granzyme B in liver tissue to investigate the roles of both the FasL and the perforin/granzyme B pathways in CHB. Reverse transcription-polymerase chain reaction was used to identify intrahepatic expression of FasL and perforin/granzyme B in liver biopsy specimens from 24 patients with hepatitis B virus (HBV) infection. In addition, the transferase-mediated deoxyuridine triphosphate nick end-labelling (TUNEL) method was used to determine the degree of apoptosis. The degree of mRNA expression and apoptosis were compared with the histologic activity index (HAI) and serology, including alanine aminotransferase (ALT). Intrahepatic mRNA expression rates of FasL, perforin and granzyme B were seen in 79.2, 62.5 and 33.3% of patients, respectively, and correlated with ALT levels (P

223 This work was supported by the fusion research program of Korea research council for industrial science and technology (B551179-1208-00, Development of Convergent Radio Therapy Equipment with O-arm CT) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea). Received 1 December 2015, Revised 28 December 2015, Accepted 28 December 2015 Correspondence: Young-Nam Kang (ynkang33@gmail.com) Tel: 82-2-2258-6849, Fax: 82-2-2258-1532 cc This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Evaluation of Dosimetric Characteristics of a Double-focused Dynamic Micro-Multileaf Collimator (DMLC)

뇌병변 등의 방사선 치료에 있어 CT (Computed Tomography) 영상만을 이용한 종양 체적(Tumor volume) 윤곽의 정확한 설정은 CT 영상의 부족한 연부조직 대조도 특성에 의하여 한계를 가진다. 따라서 자기공명영상(Magnetic Resonance Images, MRI)이 보다 정확한 목표 체적의 윤곽을 그려내기 위해 광범위 하게 사용되고 있다. 치료계획을 위해 획득한 자기공명영상에 진단단계에서 얻어진 CT영상의 전자밀도를 융합하는 방법과 자기공명 영상으로부터 만들어진 가상의 CT를 이용하는 방법 등이 자기공명 영상장치를 기반으로 한 방사선 치료 계획의 선량계산을 위하여 소개되어 왔다. 본 연구는 MRI기반의 선량계산의 가능성을 확인 해보기 위해 15명 환자의 진단 MR 영상을 통하여 Look Up Table (LUT)을 만들어 MRI 기반 선량계산과 기존의 CT 기반 선량계산을 비교 검증 하였다. 여기서 lMRI는 획득한 MR 영상에 LUT를 이용한 전자밀도 보정을 한 것이며 wMRI는 획득한 MR영상을 물 밀도로 동일화 시킨 것이다. 6 MV anterial 방향의 조사가 CT, lMRI, wMRI에 적용되어 치료계획으로 비교되었으며 또한 환자의 병변위치에 따라 2문 조사에서 5문 조사의 치료계획이 비교되었다. CT기반 치료계획을 기준으로 하여 등선량 분포와 DVH의 차이는 wMRI 보다 lMRI에서 더 적었으며 최대선량 차이가 91 cGy vs. 57 cGy, 평균선량이 74 cGy vs. 42 cGy, 최소선량 차이가 94 cGy vs. 53 cGy로 측정되어 각각의 선량 평가 면에서 그 차이가 wMRI보다 lMRI에서 더 적었다. 이러한 결과는 wMRI의 경우 공동내 선량계산에서 CT기반 선량계산과 차이가 나기 때문이다. 따라서 본 연구의 결과는 lMRI 기반 선량계산의 가능성이 있음을 보여준다. 【In the intracranial regions, an accurate delineation of the target volume has been difficult with only the CT data due to poor soft tissue contrast of CT images. Therefore, the magnetic resonance images (MRI) for the delineation of the target volumes were widely used. To calculate dose distributions with MRI-based RTP, the electron density (ED) mapping concept from the diagnostic CT images and the pseudo CT concept from the MRI were introduced. In this study, the look up table (LUT) from the fifteen patients' diagnostic brain MRI images was created to verify the feasibility of MRI-based RTP. The dose distributions from the MRI-based calculations were compared to the original CT-based calculation. One MRI set has ED information from LUT (lMRI). Another set was generated with voxel values assigned with a homogeneous density of water (wMRI). A simple plan with a single anterior 6MV one portal was applied to the CT, lMRI, and wMRI. Depending on the patient's target geometry for the 3D conformal plan, 6MV photon beams and from two to five gantry portals were used. The differences of the dose distribution and DVH between the lMRI based and CT-based plan were smaller than the wMRI-based plan. The dose difference of wMRI vs. lMRI was measured as 91 cGy vs. 57 cGy at maximum dose, 74 cGt vs. 42 cGy at mean dose, and 94 cGy vs. 53 at minimum dose. The differences of maximum dose, minimum dose, and mean dose of the wMRI-based plan were lower than the lMRI-based plan, because the air cavity was not calculated in the wMRI-based plan. These results prove the feasibility of the lMRI-based planning for brain tumor radiation therapy.】