• Journal of the Korean Society of Radiology
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• v.7 no.6
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• pp.409-414
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• 2013

In this study, we evaluated to the superiority of treatment techniques on prostate cancer, apply to each other treatment techniques-3D conformal therapy versus IMRT-using dose distribution and dose coverages. Obtained 10 patients CT simulation, divided tumor volume and critical organs. Prescription dose was 80 Gy on tumor volume and Each of plans was set by two different plans. As a result, Dose coverage was superior to IMRT. The IMRT's tumor absorbed dose(100.2%) was close to prescription doses. Normal tissue(bladder, rectal, bowel Lt Rt fumoral head) absorbed dose rate was superior. In other words, the radiation therapy of prostate cancer with intensity modulated radiation therapy was better than conformal radiation therapy on dose.

• Journal of Radiation Protection and Research
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• v.32 no.1
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• pp.21-26
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• 2007

This study is performed to evaluate the dose rate and to analyze the dose distribution of the gamma irradiation facility (IR-221) by using a Monte Calro simulation, which is helpful of upgrading the radiation processing qualification. Monte Cairo simulation is performed by MCNP4B code. Dose rates were measured at total 369 points with alanine dosimeters to compare the calculation results and the measurements data. The results have shown that the MCNP4B code is very useful to determine the dose distribution of the IR-221 gamma irradiation facility, as the calculation dose rate is within about ${\pm}5%$ of the measurement data. Dosimetry about the gamma irradiation facility usually needs enormous manpower and time. However Monte Cairo calculation method can reduce the tedious dosimetry jobs and improve the irradiation processing qualification, which will probably contribute to obtain the reliability of the irradiation products.

• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.239-246
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• 2021

Portal Dosimetry was verified using EPID to secure the clinical application and reliability of the existing research dose evaluation. The dose distribution of Geant4 was compared with the measured value by 360° rotational irradiation with a 2.5 cm cone for stereotactic brain surgery. To confirm the dose distribution of patients with brain metastasis, the dose distribution investigated by inserting a Gafchromic EBT film into the parietal phantom and the dose distribution obtained from the parietal phantom using VMAT are compared and applied to actual patients. As a result of the analysis, it was confirmed that the accuracy of the beam center and the center of the couch coincide accurately with an error within 1mm as a result of QA through a pin ball. In addition, it was confirmed that the EBT3 film has excellent linearity in the range of 0 to 10 Gy according to various dose irradiation. In the same setting as the two cervical phantoms, we confirm that the implementation and simulation results calculations of dose calculations based on Geant4 using photon beams match the experimental data within the treatment planning volume (PTV). Therefore, volume modulated arc treatment (VMAT) 360° rotational irradiation was performed, and the result of iso-dose distribution analysis by rotational irradiation confirmed that it is appropriate to include a virtual tumor.

• Progress in Medical Physics
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• v.21 no.4
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• pp.332-339
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• 2010

We aimed to setup an adaptive radiation therapy platform using cone-beam CT (CBCT) and multileaf collimator (MLC) log data and also intended to analyze a trend of dose calculation errors during the procedure based on a phantom study. We took CT and CBCT images of Catphan-600 (The Phantom Laboratory, USA) phantom, and made a simple step-and-shoot intensity-modulated radiation therapy (IMRT) plan based on the CT. Original plan doses were recalculated based on the CT ($CT_{plan}$) and the CBCT ($CBCT_{plan}$). Delivered monitor unit weights and leaves-positions during beam delivery for each MLC segment were extracted from the MLC log data then we reconstructed delivered doses based on the CT ($CT_{recon}$) and CBCT ($CBCT_{recon}$) respectively using the extracted information. Dose calculation errors were evaluated by two-dimensional dose discrepancies ($CT_{plan}$ was the benchmark), gamma index and dose-volume histograms (DVHs). From the dose differences and DVHs, it was estimated that the delivered dose was slightly greater than the planned dose; however, it was insignificant. Gamma index result showed that dose calculation error on CBCT using planned or reconstructed data were relatively greater than CT based calculation. In addition, there were significant discrepancies on the edge of each beam while those were less than errors due to inconsistency of CT and CBCT. $CBCT_{recon}$ showed coupled effects of above two kinds of errors; however, total error was decreased even though overall uncertainty for the evaluation of delivered dose on the CBCT was increased. Therefore, it is necessary to evaluate dose calculation errors separately as a setup error, dose calculation error due to CBCT image quality and reconstructed dose error which is actually what we want to know.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.373-379
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• 2022

The radiation source used for non-destructive testing have permeability and cause a scattered radiation through collisions of surrounding materials, which causes changes in the surrounding spatial dose. Therefore, this study attempted to evaluate and analyze the distribution of spatial dose by source in the working environment during the non-destructive test using monte carlo simulation. In this study, Using FLUKA, a simulation code, simulates ⁶⁰Co, ¹⁹²Ir, and ⁷⁵Se source used in non-destructive testing, The reliability of the source term was secured by comparing the calculated dose rate with the data of the Health and Physics Association. After that, a non-destructive test in the radiation safety facility(RT-room) was designed to evaluate the spatial dose according to the distance from the source. As a result of the spatial dose evaluation, ⁷⁵Se source showed the lowest dose distribution in the frontal position and ⁶⁰Co source showed a dose rate of about 15 times higher than that of ⁷⁵Se and about 2 times higher than that of ¹⁹²Ir. In addition, the spatial dose according to the distance tends to decrease according to the distance inverse square law as the distance from the source increases. Exceptionally, ⁶⁰Co, ¹⁹²Ir, and ⁷⁵Se sources confirmed a slight increase within 2 m of position. Based on the results of this study, it is believed that it will be used as supplementary data for safety management of workers in radiation safety facilities during non-destructive testing using radioactive isotopes.

• Progress in Medical Physics
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• v.23 no.2
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• pp.106-113
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• 2012

The purpose of this study is to evaluate the variation of radiation dose distribution for liver tumor located in liver dome and for the interest organs(normal liver, kidney, stomach) with the pencil beam convolution (PBC) algorithm versus anisotropic Analyticalal algorithm (AAA) of the Varian Eclipse treatment planning system, The target volumes from 20 liver cancer patients were used to create treatment plans. Treatment plans for 10 patients were performed in Stereotactic Body Radiation Therapy (SBRT) plan and others were performed in 3 Dimensional Conformal Radiation Therapy (3DCRT) plan. dose calculation was recalculated by AAA algorithm after dose calculation was performed by PBC algorithm for 20 patients. Plans were optimized to 100% of the PTV by the Prescription Isodose in Dose Calculation with the PBC algorithm. Plans were recalculated with the AAA, retaining identical beam arrangements, monitor units, field weighting and collimator condition. In this study, Total PTV was to be statistically significant (SRS: p=0.018, 3DCRT: p=0.006) between PBC and AAA algorithm. and in the case of PTV, ITV in liver dome, plans for 3DCRT were to be statistically significant respectively (p=0.013, p=0.024). normal liver and kidney were to be statistically significant (p=0.009, p=0.037). For the predictive index of dose variation, CVF ratio was to be statistically significant for PTV in the liver dome versus PTV (SRS r=0.684, 3DCRT r=0.732, p<0.01) and CVF ratio for Tumor size was to be statistically significant (SRS r=-0.193, p=0.017, 3DCRT r=0.237, p=0.023).

• Progress in Medical Physics
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• v.22 no.2
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• pp.61-66
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• 2011

In this study, we evaluated the effect of grid size on dose calculation accuracy using 2 head & neck and 2 prostate IMRT cases and based on this study's findings, we also evaluated the efficiency of a 2D diode array detector for IMRT quality assurance. Dose distributions of four IMRT plan data were calculated at four calculation grid sizes (1.25, 2.5, 5, and 10 mm) and the calculated dose distributions were compared with measured dose distributions using 2D diode array detector. Although there was no obvious difference in pass rate of gamma analysis with 3 mm/3% acceptance criteria for the others except 10 mm grid size, we found that the pass rates of 2.5, 5 and 10 mm grid size were decreased 5%, 20% and 31.53% respectively according to the application of the fine acceptance criteria, 3 mm/3%, 2 mm/2% and 1 mm/1%. The calculation time were about 11.5 min, 4.77 min, 2.95 min, and 11.5 min at 1.25, 2.5, 5, and 10 mm, respectively and as the grid size increased to double, the calculation time decreased about one-half. The grid size effect was observed more clearly in the high gradient area than the low gradient area. In conclusion, 2.5 mm grid size is considered acceptable for most IMRT plans but at least in the high gradient area, 1.25 mm grid size is required to accurately predict the dose distribution. These results are exactly same as the precious studies' results and theory. So we confirmed that 2D array diode detector was suitable for the IMRT QA.

• Progress in Medical Physics
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• v.27 no.2
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• pp.93-97
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• 2016

In this study, we evaluate the effect of respiration on the dose distribution in patient target volume (PTV) during intensity-modulated radiation therapy (IMRT) and research methods to reduce this impact. The dose distributions, homogeneity index (HI), coverage index (CVI), and conformity index of the PTV, which is calculated from the dose-volume histogram (DVH), are compared between the maximum intensity projection (MIP) image-based plan and other images at respiration phases of 30%, 60% and 90%. In addition, the reducing effect of complication caused by patient respiration is estimated in the case of a bolus and the expended PTV on the skin. The HI is increased by approximately twice, and the CVI is relatively decreased without the bolus at other respiration phases. With the bolus and expended PTV, the change in the dose distribution of the PTV is relatively small with patient respiration. Therefore, the usage of the bolus and expended PTV can be considered as one of the methods to improve the accuracy of IMRT in the treatment of breast cancer patients with respiratory motion.

• Progress in Medical Physics
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• v.26 no.3
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• pp.160-167
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• 2015

Radiation exposure from medical diagnostic imaging procedures to patients is one of the most significant interests in diagnostic x-ray system. A miniature x-ray intraoral tube was developed for the first time in the world which can be inserted into the mouth for imaging. Dose evaluation should be carried out in order to utilize such an imaging device for clinical use. In this study, dose evaluation of the new x-ray unit was performed by 1) using a custom made in vivo Pig phantom, 2) determining exposure condition for the clinical use, and 3) measuring patient dose of the new system. On the basis of DRLs (Diagnostic Reference Level) recommended by KDFA (Korea Food & Drug Administration), the ESD (Entrance Skin Dose) and DAP (Dose Area Product) measurements for the new x-ray imaging device were designed and measured. The maximum voltage and current of the x-ray tubes used in this study were 55 kVp, and 300 mA. The active area of the detector was $72{\times}72mm$ with pixel size of $48{\mu}m$. To obtain the operating condition of the new system, pig jaw phantom images showing major tooth-associated tissues, such as clown, pulp cavity were acquired at 1 frame/sec. Changing the beam currents 20 to $80{\mu}A$, x-ray images of 50 frames were obtained for one beam current with optimum x-ray exposure setting. Pig jaw phantom images were acquired from two commercial x-ray imaging units and compared to the new x-ray device: CS 2100, Carestream Dental LLC and EXARO, HIOSSEN, Inc. Their exposure conditions were 60 kV, 7 mA, and 60 kV, 2 mA, respectively. Comparing the new x-ray device and conventional x-ray imaging units, images of the new x-ray device around teeth and their neighboring tissues turn out to be better in spite of its small x-ray field size. ESD of the new x-ray device was measured 1.369 mGy on the beam condition for the best image quality, 0.051 mAs, which is much less than DRLs recommended by IAEA (International Atomic Energy Agency) and KDFA, both. Its dose distribution in the x-ray field size was observed to be uniform with standard deviation of 5~10 %. DAP of the new x-ray device was $82.4mGy*cm^2$ less than DRL established by KDFA even though its x-ray field size was small. This study shows that the new x-ray imaging device offers better in image quality and lower radiation dose compared to the conventional intraoral units. In additions, methods and know-how for studies in x-ray features could be accumulated from this work.

• Progress in Medical Physics
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• v.21 no.2
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• pp.127-136
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• 2010

Emerging technologies such as four-dimensional computed tomography (4D CT) is expected to allow clinicians to accurately model interfractional motion and to quantitatively estimate internal target volumes (ITVs) for radiation therapy involving moving targets. A need exists for a 4D radiation therapy quality assurance (QA) device that can incorporate and analyze the patient specific intrafractional motion as it relate to dose delivery and respiratory gating. We built a 4D RT prototype device and analyzed the patient-specific 4D radiation therapy QA for 2D dose distributions successfully. With more improvements, the 4D RT QA prototype device could be an integral part of a 4D RT decision process to confirm the dose delivery.