• Radiation Oncology Journal
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• v.17 no.3
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• pp.223-229
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• 1999

Purpose : The expression pattern of c-jun by ionizing radiation according to cell growth state (exponential growth vs. stationary phase) and its relationship with cell cycle redistribution were investigated. Materials and Methods : The exponential growth phase (day 4) and stationary phase (day 9) cells were determined from cell growth curve according to the elapse of days in CaSki. The cells were irradiated using 6 MV X-ray with a dose of 2 Gy at a fixed dose rate of 3 Gy/min. Northern blot analysis was peformed with total cellular RNA and cell cycle distribution was analyzed using flow cytometry according to time-course after irradiation. Results : The maximum expression of c-jun occurred 1 hour after irradiation in both exponential growth and stationary phase cells. After then c-jun expression was elevated upto 6 hours in exponential growth phase cells, but the level decreased in stationary phase cells. Movements of cells from G0-G1 to S, G2-M phase after irradiation were higher in exponential growth phase than stationary phase. Conclusion : c-jun may be involved in the regulation of cellular proliferation according to the growth states after irradiation.

• Progress in Medical Physics
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• v.24 no.1
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• pp.35-40
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• 2013

Recently, the uses of Multi-Detector Computed Tomography (MDCT) for radiation treatment simulation and planning which is used for intensity modulated radiation therapy with high technique are increasing. Because of the increasing uses of MDCT, additional doses are also increasing. The objective of this study is to evaluate the absorbed dose of body and skin undergoing in MDCT scans. In this study, the exposed dose at the surface and the center of the cylindrical water phantom was measured using an pencil ionization chamber, 30 cc ionization chamber and TL Powder. The results of MDCT were 31.84 mGy, 33.58 mGy and 32.73 mGy respectively. The absorbed dose at the surface showed that the TL reading value was 33.92 mGy from MDCT. These results showed that the surface dose was about 3.5% from the MDCT exposure higher than a dose which is located at the center of the phantom. These results mean that the total exposed dose undergoing MDCT 4 times (diagnostic, radiation therapy planning, follow-up et al.), is about 14 cGy, and have to be considered significantly to reduce the exposed dose from CT scan.

• Progress in Medical Physics
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• v.23 no.4
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• pp.219-228
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• 2012

The tangential breast intensity modulated radiotherapy (T-B IMRT) technique, which uses the same tangential fields as conventional 3-dimensional conformal radiotherapy (3D-CRT) plans with physical wedges, was analyzed in terms of the calculated dose distribution feature and dosimetric accuracy of beam delivery during treatment. T-B IMRT plans were prepared for 15 patients with breast cancer who were already treated with conventional 3D-CRT. The homogeneity of the dose distribution to the target volume was improved, and the dose delivered to the normal tissues and critical organs was reduced compared with that in 3D-CRT plans. Quality assurance (QA) plans with the appropriate phantoms were used to analyze the dosimetric accuracy of T-B IMRT. An ionization chamber placed at the hole of an acrylic cylindrical phantom was used for the point dose measurement, and the mean error from the calculated dose was $0.7{\pm}1.4%$. The accuracy of the dose distribution was verified with a 2D diode detector array, and the mean pass rate calculated from the gamma evaluation was $97.3{\pm}2.9%$. We confirmed the advantages of a T-B IMRT in the dose distribution and verified the dosimetric accuracy from the QA performance which should still be regarded as an important process even in the simple technique as T-B IMRT in order to maintain a good quality.

• Journal of the Korean Society of Radiology
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• v.10 no.5
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• pp.313-320
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• 2016

This research has been conducted to investigate the method of reducing patients' radiation exposure during X-ray imaging of Both Hip Ap examination by removing the grid. When using the grid with 60 kV and a non-filter, the Entrance Surface Dose was 4.77 mGy, and the result was highest and 34 times higher than the lowest measurement when removing the grid with 90 kV, and 0.3 mmCu filter. Based on the ICRP Pub. 60 at the level of 70 kV, the Effective Dose of testis and ovary was 0.255 mSv when using the grid, and that result was approximately 5.2 times higher than the 0.049 mSv when removing the grid. Based on the ICRP Pub. 103 at the level of 70 kV, the Effective Dose of testis and ovary was 0.090 mSv when using the grid, and that result was approximately 4.5 times higher than the 0.020 mSv when removing the grid. When using the grid, the range of Exposure Index was 671 to 782, and when removing the grid, the range of Exposure Index was 513 to 606, and both results were at optimal exposure conditions and valid diagnostic imaging after evaluations. Therefore, removing the grid during X-ray imaging of Both Hip Ap will help reduce patients radiation exposure.

• Progress in Medical Physics
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• v.25 no.4
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• pp.193-198
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• 2014

The purpose of this study is to see the feasibility of the newly developed 2D dosimetry system using phosphor screen for helical tomotherapy. The cylindrical water phantom was fabricated with phosphor screen to emit the visible light during irradiation. There are three types of virtual target, one is one spot target, another is C-shaped target, and the other is multiple targets. Each target was planned to be treated at 10 Gy by treatment planning system (TPS) of tomotherapy. The cylindrical phantom was placed on the tomotherapy table and irradiated as calculations of the TPS. Every frame which acquired by CCD camera was integrated and the doses were calculated in pixel by pixel. The dose distributions from the fluorescent images were compared with the calculated dose distribution from the TPS. The discrepancies were evaluated as gamma index for each treatment. The curve for dose rate versus pixel value was not saturated until 900 MU/min. The 2D dosimetry using the phosphor screen and the CCD camera is respected to be useful to verify the dose distribution of the tomotherapy if the linearity correction of the phosphor screen improved.

• Journal of the Korean Society of Radiology
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• v.17 no.1
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• pp.37-46
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• 2023

This study aims to evaluate the usefulness of Deep Learning Image Reconstruction (TrueFidelity, TF), the image quality of existing Filtered Back Projection (FBP) and Adaptive Statistical Iterative Reconstruction-Veo (ASIR-V) were compared. Noise, CNR, and SSIM were measured by obtaining images with doses fixed at 17.29 mGy and altered to 10.37 mGy, 12.10 mGy, 13.83 mGy, and 15.56 mGy in reconstruction techniques of FBP, ASIR-V 50%, and TF-H. TF-H has superior image quality compared to FBP and ASIR-V when the reconstruction technique change is given at 17.29 mGy. When dose changes were made, Noise, CNR, and SSIM were significantly different when comparing 10.37 mGy TF-H and FBP (p<0.05), and no significant difference when comparing 10.37 mGy TF-H and ASIR-V 50% (p>0.05). TF-H has a dose-reduction effect of 30%, as the highest dose of 15.56 mGy ASIR-V has the same image quality as the lowest dose of 10.37 mGy TF-H. Thus, Deep Learning Reconstruction techniques (TF) were able to reduce dose compared to Iterative Reconstruction techniques (ASIR-V) and Filtered Back Projection (FBP). Therefore, it is considered to reduce the exposure dose of patients.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.217-224
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• 2014

Purpose : Conventional, IMRT, at CSI treatment with VMAT, this study compare the treatment plan with dose changes measured at Junction field according to the error of Setup. Materials and Methods : This study established Conventional, the IMRT, VMAT treatment planning for CSI therapy using the Eclipse 10.0 (Eclipse10.0, Varian, USA) and chose person in Seoul National University Hospital. Verification plan was also created to apply IMRT QA phantom for each treatment plan to the film measurements. At this time, the error of Setup was applied to the 2, 4, 6mm respectively with the head and foot direction. ("+" direction of the head, "-" means that the foot direction.) Using IMRT QA Phantom and EBT2 film, was investigated by placing the error of Setup for each Junction. We check the consistency of the measured Film and plan dose distribution by gamma index (Gamma index, ${\gamma}$). In addition, we compared the error of Setup by the dose distribution, and analyzing the uniformity of the dose distribution within the target by calculating the Homogeneity Index (HI). Results : It was figured out that 90.49%-gamma index we obtained with film is agreement with film scan score and dose distribution of treatment plan. Also, depend on the dose distribution on distance, if we make the error of Setup 2, 4, 6mm in the head direction, it showed that 3.1, 4.5, 8.1 at $^*Diff$(%) of Conventional, 1.1, 3.5, 6.3 at IMRT, and 1.6, 2.5, 5.7 at VMAT. In the same way, if we make the error of Setup 2, 4, 6mm in the foot direction, it showed that -1.6, -2.8, -4.4 at $^*Diff$(%) of Conventional, -0.9, -1.6, -2.9 at IMRT, and -0.5, -2.2, -2.5 at VMAT. Homogeneity Index(HI)s are 1.216 at Conventional, 1.095 at IMRT and 1.069 at VMAT. Discussion and Conclusion : The dose-change depend on the error of Setup at the CSI RT(radiation therapy) using IMRT and VMAT which have advantages, Dose homogeneity and the gradual dose gradients on the Junction part is lower than that of Conventional CSI RT. This a little change of dose means that there is less danger on patients despite of the error of Setup generated at the CSI RT.

• Journal of the Korean Society of Radiology
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• v.12 no.5
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• pp.659-667
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• 2018

The purpose of this study was to determine the effect of body mass index (BMI) on entrance surface air kerma (ESAK) in abdominal X-ray radiography using automatic exposure control (AEC). This study included 321 patients who underwent abdominal X-ray using AEC, and we correlated ESAK with height, weight, BMI and compared mean ESAK according to BMI grades (Underweight, Normal, Overweight, Obese 1, Obese 2). As a result, Weight ($R^2=0.777$, p<.001) and BMI ($R^2=0.835$, p<.001) were positively associated with ESAK, but no significant association was found between height ($R^2=0.075$, p<.001) and ESAK. The mean ESAK with respect to BMI grades showed statistically significant difference and in the post-hoc analysis, the existence of 5 subgroups at the significance level of 0.05 indicated that there were differences in the ESAK in all BMI grades. Also, as the increment of ESAK between two neighboring BMI grades increases from Underweight to Obese 2, the exposure dose dramatically increased as the BMI increased. Thus, an excessive exposure dose due to increasing BMI when using AEC should be acknowledged and Efforts to reduce dose should be taken, such as: by fixing the exposure conditions.

• Journal of the Korean Society of Radiology
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• v.17 no.5
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• pp.685-691
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• 2023

This study aims to raise awareness of the exposure index according to the Sub-ROI in clinical use by studying the effect of Sub-ROI's change on exposure index and dose during Chest PA examination. In this study, to examine the changes in EI and ESD according to the Sub-ROI setting, the irradiation conditions were set to 120 kVp, 200 mA, 2 mAs, and the SID was fixed to 180cm. Five types of Sub-ROI were used. The average value of EI according to the Sub-ROI's change was 135.58 ± 0.89 in AEC, 100.80 ± 0.80 in VR, 143.43 ± 0.76 in HR, 103.22 ± 0.68 in LS, and 102.79 ± 0.84 in SS. The mean value of ESD was 30.28±0.50 µGy in AEC, 30.16 ± 0.44 µGy in VR, 30.30 ± 0.46 µGy in HR, 30.23 ± 0.46 µGy in LS, and 30.28 ± 0.51 µGy in SS. As a result of this study, based on the AEC mode recommended by the manufacturer, the VR (25.7%), LS (23.9%), and SS (24.2%) modes decreased, and the HR mode increased by 5.7%. However, ESD was not affected by the Sub-ROI's change. Therefore, Sub-ROI may change EI during the Chest PA examination, it is considered that Sub-ROI should be used appropriately when setting protocols in clinical use.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.239-245
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• 2014

Purpose : The purpose of this study is to verify the accuracy of dose delivery according to the pitch and roll rotational setup error with 6D robotic couch in Intensity Modulated Radiation Therapy (IMRT) for pelvic region in patients. Materials and Methods : Trilogy(Varian, USA) and 6D robotic couch(ProturaTM 1.4, CIVCO, USA) were used to measure and analyze the rotational setup error of 14 patients (157 setup cases) for pelvic region. The total 157 Images(CBCT 78, Radiography 79) were used to calculate the mean value and the incidence of pitch and roll rotational setup error with Microsoft Office Excel 2007. The measured data (3 mm, 3%) at the reference angle ($0^{\circ}$) without couch rotation of pitch and roll direction was compared to the others at different pitch and roll angles ($1^{\circ}$, $1.5^{\circ}$, $2^{\circ}$, $2.5^{\circ}$) to verify the accuracy of dose delivery by using 2D array ionization chamber (I'mRT Matrixx, IBA Dosimetry, Germany) and MultiCube Phantom(IBA Dosimetry, Germany). Result from the data, gamma index was evaluated. Results : The mean values of pitch and roll rotational setup error were $0.9^{\circ}{\pm}0.7$, $0.5^{\circ}{\pm}0.6$. The maximum values of them were $2.8^{\circ}$, $2.0^{\circ}$. All of the minimum values were zero. The mean values of gamma pass rate at four different pitch angles ($1^{\circ}$, $1.5^{\circ}$, $2^{\circ}$, $2.5^{\circ}$) were 97.75%, 96.65%, 94.38% and 90.91%. The mean values of gamma pass rate at four different roll angles ($1^{\circ}$, $1.5^{\circ}$, $2^{\circ}$, $2.5^{\circ}$) were 93.68%, 93.05%, 87.77% and 84.96%. when the same angles ($1^{\circ}$, $1.5^{\circ}$, $2^{\circ}$) of pitch and roll were applied simultaneously, The mean values of each angle were 94.90%, 92.37% and 87.88%, respectively. Conclusion : As a result of this study, it was able to recognize that the accuracy of dose delivered is lowered gradually as pitch and roll increases. In order to increase the accuracy of delivered dose, therefore, it is recommended to perform IGRT or correct patient's position in the pitch and roll direction, to improve the quality of treatment.