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  • Original Article 2016-12-31 2016-12-31 \ 0 \ 236 \ 159

    Analysis of Physical Properties for Various Compositions of Reusable LMG and LCV Micelle Gel

    Jin Mook Kang, Dong Han Lee, Yu Ra Cho, Seon Bung Hwang, Young Hoon Ji, So Hyun Ahn, Ki Chang Keum, Re Na Lee, Sam Ju Cho, Insup Noh

    Abstract
    In this study, we evaluated the reusable leuco malachite green (LMG) micelle gel properties dependent on various components of chemical concentration and compared with leuco crystal violet (LCV). The gels were delivered to 10, 20, 30, 40 and 50 Gy at 6 MV photon beam from linear accelerator and analyzed using spectrophotometry. We confirmed that the reusable LMG and LVC absorbance wavelength peak were made up at 630 nm and 600 nm respectively. The transparency of reusable LMG decreased with higher amount of trichloroacetic acid (TCAA) and lower reusable LMG dyes. 1 mM reusable LMG was the lowest transparency. The sensitivity was increased depending on lower trichloroacetic acid (TCAA) concentrations and the amount of suitable surfactant (Triton X-100), which was found to be 7 mM. However, we were not able to investigate sensitivity effects factor from reusable LMG dyes. The gel dosimeter containing 16 mM TCAA, 7 mM Triton X-100 gel dosimeter showed the highest sensitivity at 0.0021±0.0001 cm−1. Gy−1. The sensitivity of LCV was found to be higher than reusable LMG at 0.0037±0.0005 cm−1. Gy−1. The reusable LMG and LCV dose responses were shown to be R2=0.997, R2=0.999 respectively, as stable measurement results. Future research is necessary to improve dose sensitivity, dose rate dependency and gel fading with extensive chemical formulations.
  • Original Article 2016-12-31 2016-12-31 \ 0 \ 544 \ 223

    Dosimetric Validation of the Acuros XB Advanced Dose Calculation Algorithm for Volumetric Modulated Arc Therapy Plans

    So-Yeon Park, Jong Min Park, Chang Heon Choi, Minsoo Chun, Jung-in Kim

    Abstract
    Acuros XB advanced dose calculation algorithm (AXB, Varian Medical Systems, Palo Alto, CA) has been released recently and provided the advantages of speed and accuracy for dose calculation. For clinical use, it is important to investigate the dosimetric performance of AXB compared to the calculation algorithm of the previous version, Anisotropic Analytical Algorithm (AAA, Varian Medical Systems, Palo Alto, CA). Ten volumetric modulated arc therapy (VMAT) plans for each of the following cases were included: head and neck (H&N), prostate, spine, and lung. The spine and lung cases were treated with stereotactic body radiation therapy (SBRT) technique. For all cases, the dose distributions were calculated using AAA and two dose reporting modes in AXB (dose-to-water, AXBw, and dose-to-medium, AXBm) with same plan parameters. For dosimetric evaluation, the dose-volumetric parameters were calculated for each planning target volume (PTV) and interested normal organs. The differences between AAA and AXB were statistically calculated with paired t-test. As a general trend, AXBw and AXBm showed dose underestimation as compared with AAA, which did not exceed within −3.5% and −4.5%, respectively. The maximum dose of PTV calculated by AXBw and AXBm was tended to be overestimated with the relative dose difference ranged from 1.6% to 4.6% for all cases. The absolute mean values of the relative dose differences were 1.1±1.2% and 2.0±1.2% when comparing between AAA and AXBw, and AAA and AXBm, respectively. For almost dose-volumetric parameters of PTV, the relative dose differences are statistically significant while there are no statistical significance for normal tissues. Both AXBw and AXBm was tended to underestimate dose for PTV and normal tissues compared to AAA. For analyzing two dose reporting modes in AXB, the dose distribution calculated by AXBw was similar to those of AAA when comparing the dose distributions between AAA and AXBm.
  • Original Article 2016-12-31 2016-12-31 \ 0 \ 332 \ 188

    Feasibility Study of a Custom-made Film for End-to-End Quality Assurance Test of Robotic Intensity Modulated Radiation Therapy System

    Juhye Kim, Kwangwoo Park, Jeongmin Yoon, Eungman Lee, Samju Cho, Sohyun Ahn, Jeongeun Park, Wonhoon Choi, Ho Lee

    Abstract
    This paper aims to verify the clinical feasibility of a custom-made film created by a laser cutting tool for End-to-End (E2E) quality assurance in robotic intensity modulated radiation therapy system. The custom-made film was fabricated from the Gafchromic EBT3 film with the size of 8”×10” using a drawing that is identical to the shape and scale of the original E2E film. The drawing was created by using a computer aided design program with the image file, which is obtained by scanning original E2E film. Beam delivery and evaluations were respectively performed with the original film and the custom-made film using fixed-cone collimator on three tracking modes: 6D skull (6DS), Xsight spine (XS), and Xsight lung (XL). The differences between total targeting errors of the original and custom-made films were recorded as 0.17 mm, 0.3 mm, and 0.17 mm at 6DS, XS, and XL tracking modes, respectively. This indicates that the custom-made film could yield nearly equivalent results to those of the original E2E film, given the uncertainties caused by distortions during film scanning and vibrations associated with film cutting. By confirming the clinical feasibility of a custom-made film for E2E testing, it can be expected that economic efficiency of the testing will increase accordingly.
  • Original Article 2016-12-31 2016-12-31 \ 0 \ 508 \ 191

    Customized 3D Printed Bolus for Breast Reconstruction for Modified Radical Mastectomy (MRM)

    Jin-Suk Ha, Jae Hong Jung, Min-Joo Kim, Mi Jin Jeon, Won Suk Jang, Yoon Jin Cho, Ik Jae Lee, Jun Won Kim, Tae Suk Suh

    Abstract
    We aim to develop the breast bolus by using a 3D printer to minimize the air-gap, and compare it to commercial bolus used for patients undergoing reconstruction in breast cancer. The bolus-shaped region of interests (ROIs) were contoured at the surface of the intensity-modulated radiation therapy (IMRT) thorax phantom with 5 mm thickness, after which the digital imaging and communications in mdicine (DICOM)-RT structure file was acquired. The intensity-modulated radiation therapy (Tomo-IMRT) and direct mode (Tomo-Direct) using the Tomotherapy were established. The 13 point doses were measured by optically stimulated luminescence (OSLD) dosimetry. The measurement data was analyzed to quantitatively evaluate the applicability of 3D bolus. The percentage change of mean measured dose between the commercial bolus and 3D-bolus was 2.3% and 0.7% for the Tomo-direct and Tomo-IMRT, respectively. For air-gap, range of the commercial bolus was from 0.8 cm to 1.5 cm at the periphery of the right breast. In contrast, the 3D-bolus have occurred the air-gap (i.e., 0 cm). The 3D-bolus for radiation therapy reduces the air-gap on irregular body surface that believed to help in accurate and precise radiation therapy due to better property of adhesion.
  • Original Article 2016-12-31 2016-12-31 \ 0 \ 373 \ 159

    Evaluating Correlation between Geometrical Relationship and Dose Difference Caused by Respiratory Motion Using Statistical Analysis

    Dong-Seok Shin, Seong-Hee Kang, Dong-Su Kim, Tae-Ho Kim, Kyeong-Hyeon Kim, Min-Seok Cho, Yu-Yoon Noh, Do-Kun Yoon, Tae Suk Suh

    Abstract
    Dose differences between three-dimensional (3D) and four-dimensional (4D) doses could be varied according to the geometrical relationship between a planning target volume (PTV) and an organ at risk (OAR). The purpose of this study is to evaluate the correlation between the overlap volume histogram (OVH), which quantitatively shows the geometrical relationship between the PTV and OAR, and the dose differences. 4D computed tomography (4DCT) images were acquired for 10 liver cancer patients. Internal target volume-based treatment planning was performed. A 3D dose was calculated on a reference phase (end-exhalation). A 4D dose was accumulated using deformation vector fields between the reference and other phase images of 4DCT from deformable image registration, and dose differences between the 3D and 4D doses were calculated. An OVH between the PTV and selected OAR (duodenum) was calculated and quantified on the basis of specific overlap volumes that corresponded to 10%, 20%, 30%, 40%, and 50% of the OAR volume overlapped with the expanded PTV. Statistical analysis was performed to verify the correlation with the OVH and dose difference for the OAR. The minimum mean dose difference was 0.50 Gy from case 3, and the maximum mean dose difference was 4.96 Gy from case 2. The calculated range of the correlation coefficients between the OVH and dose difference was from −0.720 to −0.712, and the R-square range for regression analysis was from 0.506 to 0.518 (p-value <0.05). However, when the 10% overlap volume was applied in the six cases that had OVH value ≤2, the average percent mean dose differences were 34.80±12.42%. Cases with quantified OVH values of 2 or more had mean dose differences of 29.16±11.36%. In conclusion, no significant statistical correlation was found between the OVH and dose differences. However, it was confirmed that a higher difference between the 3D and 4D doses could occur in cases that have smaller OVH value.
  • Original Article 2016-12-31 2016-12-31 \ 0 \ 506 \ 189

    Feasibility Study of Source Position Verification in HDR Brachytherapy Using Scintillating Fiber

    Sun Young Moon, EunHee Jeong, Young Kyung Lim, Weon Kyu Chung, Hyun Do Huh, Dong Wook Kim, Myonggeun Yoon

    Abstract
    The position verification of the radiation source utilized in brachytherapy forms a critical factor in determining the therapeutic efficiency. Currently, films are used to verify the source position; however, this method is encumbered by the lengthy time interval required from film scanning to analysis, which makes real-time position verification difficult. In general, the source position accuracy is usually tested in a monthly quality assurance check. In this context, this study investigates the feasibility of the real-time position verification of the radiation source in high dose rate (HDR) brachytherapy with the use of scintillating fibers. To this end, we construct a system consisting of scintillating fibers and a silicon photomultiplier (SiPM), optimize the dosimetric software setup and radiation system characteristics to obtain maximum measurement accuracy, and determine the relative ratio of the measured signals dependent upon the position of the scintillating fiber. According to the dosimetric results based on a treatment plan, in which the dwell time is set at 30 and 60 s at two dwell positions, the number of signals is 31.5 and 83, respectively. In other words, the signal rate roughly doubles in proportion to the dwell time. The source position can also be confirmed at the same time. With further improvements in the spatial resolution and scintillating fiber array, the source position can be verified in real-time in clinical settings with the use of a scintillating fiber-based system.
  • Original Article 2016-12-31 2016-12-31 \ 0 \ 277 \ 154

    An Empirical Approach to Dosimetric Effect of Carbon Fiber Couch for Flattening Filter Free Beam of Elekta LINAC

    Sohyun Ahn, Kwangwoo Park, Jinsung Kim, Ho Lee, Jeongmin Yoon, Eungman Lee, Sohyun Park, Jeongeun Park, Juhye Kim, Ki Chang Keum

    Abstract
    Generally, it is recommended that the dosimetric effect of carbon fiber couch should be considered especially for an intensity-modulated therapy with a large portion of monitor units from posterior angles. Even a flattening filter free (FFF) beam has been used for stereotactic body radiation therapy (SBRT), the effect of carbon fiber couch for FFF beam is not well known. This work is an effort to evaluate the dosimetric effect of carbon fiber couch for flattened and FFF beam of Elekta linac empirically. The absorbed doses were measured with Farmer type chamber and water-equivalent phantoms with and without couch. And differences of the absorbed doses between with and without couch defined as “couch effect”. By comparing calculated dose in treatment planning system (TPS) with measured dose, the optimal density of couch was evaluated. Finally, differences on patient’s skin dose and target dose by couch were evaluated in TPS. As a result, the couch effect for 6 and 10 MV flattened beam were −2.71% and −2.32%, respectively. These values were agreed with provided data by vendor within 0.5%. The couch effect for 6 and 10 MV FFF beam were −3.75% and −2.80%, respectively. The patient’s skin dose was increased as 18.6% and target dose was decreased as 0.87%, respectively. It was realized that the couch effect of FFF beam was more severe than that of flattened beam. Patient’s skin dose and target dose were changed by the couch effect.
  • Original Article 2016-12-31 2016-12-31 \ 0 \ 305 \ 153

    Comparison of Temperature Distribution in Agar Phantom and Gel Bolus Phantom by Radiofrequency Hyperthermia

    Dong Kyung Jung, Sung Kyu Kim, Joon Ha Lee, Sang Mo Youn, Hyung Dong Kim, Se An Oh, Jae Won Park, Ji Won Yea

    Abstract
    The usefulness of Gel Bolus phantom was investigated by comparing the temperature distribution characteristic of the agar phantom produced to investigate the dose distribution characteristic of radiofrequency hyperthermia device with that of the Gel Bolus phantom under conditions similar to those of an agar phantom that can continuously carry out temperature measurement. The temperatures of the agar phantom and the Gel Bolus phantom were raised to 36.5±3oC and a temperature sensing was inserted at depths of 5, 10, and 15 cm from the phantom central axis. The temperature increase rate and the coefficient of determination were analyzed while applying output powers of 100 W and 150 W, respectively, at intervals of 1 min for 60 min under conditions where the indoor temperature was in the range 24.5∼27.5oC, humidity was 35∼40%, internal cooling temperature of the electrode was 20oC, size of the upper electrode was 250 mm, and the size of the lower electrode was 250 mm. The coefficients of determination of 150 W output power at the depth point of 5 cm from the central axis of the phantom were analyzed to be 0.9946 and 0.9926 in the agar and Gel Bolus phantoms, respectively; moreover, the temperature change equation of the agar and Gel Bolus phantoms with time can be expressed as follows in the state the phantom temperature is raised to 36oC: Y(G) is equation of Gel Bolus phantoms (in 5 cm depth) applying output power of 150 W. Y(G)=0.157X+36. It can be seen that if the temperature is measured in this case, the Gel Bolus phantom value can be converted to the measured value of the agar phantom. As a result of comparing the temperature distribution characteristics of the agar phantom of a human-body-equivalent material with those of the Gel Bolus phantom that can be continuously used, the usefulness of Gel Bolus phantom was exhibited.
  • Original Article 2016-12-31 2016-12-31 \ 0 \ 531 \ 220

    Development Treatment Planning System Based on Monte-Carlo Simulation for Boron Neutron Capture Therapy

    Moo-Sub Kim, Kazuki Kubo, Hajime Monzen, Do-Kun Yoon, Han-Back Shin, Sunmi Kim, Tae Suk Suh

    Abstract
    The purpose of this study is to develop the treatment planning system (TPS) based on Monte-Carlo simulation for BNCT. In this paper, we will propose a method for dose estimation by Monte-Carlo simulation using the CT image, and will evaluate the accuracy of dose estimation of this TPS. The complicated geometry like a human body allows defining using the lattice function in MCNPX. The results of simulation such as flux or energy deposition averaged over a cell, can be obtained using the features of the tally provided by MCNPX. To assess the dose distribution and therapeutic effect, dose distribution was displayed on the CT image, and dose volume histogram (DVH) was employed in our developed system. The therapeutic effect can be efficiently evaluated by these evaluation tool. Our developed TPS could be effectively performed creating the voxel model from CT image, the estimation of each dose component, and evaluation of the BNCT plan.
  • Original Article 2016-12-31 2016-12-31 \ 0 \ 254 \ 156

    Conceptual Study of Brain Dedicated PET Improving Sensitivity

    Han-Back Shin, Yong Choi, Yoonsuk Huh, Jin Ho Jung, Tae Suk Suh

    Abstract
    The purpose of this study is to propose a novel high sensitivity neuro-PET design. The improvement of sensitivity in neuro-PET is important because it can reduce scan time and/or radiation dose. In this study, we proposed a novel PET detector design that combined conical shape detector with cylindrical one to obtain high sensitivity. The sensitivity as a function of the oblique angle and the ratio of the conical to cylindrical portion was estimated to optimize the design of brain PET using Monte Carlo simulation tool, GATE. An axial sensitivity and misplacement rate by penetration of γ rays were also estimated to evaluate the performance of the proposed PET. The sensitivity was improved by 36% at the center of axial FOV. This value was similar to the calculated value. The misplacement rate of conical shaped PET was about 5% higher than the conventional PET. The results of this study demonstrated the conical detector proposed in this study could provide subsequent improvement in sensitivity which could allow to design high sensitivity PET for brain imaging.
Korean Society of Medical Physics

Vol.35 No.3
2016-12-31

pISSN 2508-4445
eISSN 2508-4453
Formerly ISSN 1226-5829

Frequency: Quarterly

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