• The Journal of Korean Society for Radiation Therapy
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• v.25 no.1
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• pp.25-31
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• 2013

Purpose: The aim of this study is to evaluate the dosimetric properties of robust planning strategy for plain intensity-modulated proton therapy (IMPT) taking into account of the uncertainties of effective proton range and set up error as compared to photon intensity-modulated radiation therapy (photon-IMRT) in prostate cancer treatment. Materials and Methods: The photon-IMRT (7 beams, step & shoot), plain-IMPT (2, 4, and 7 portals), and robust- IMPT plans, which was recalculated the plain-IMPT based on the uncertainties of range error (${\pm}5%$) and set up error (0.5 cm), were evaluated for five prostate cancer patients prescribed by 70 Gy/35 fractions. To quantitatively evaluate the dose distributions, several parameters such as maximum dose, minimum dose, mean dose, conformity index (CI), and homogeneity index (HI) for PTV as well as dose-volume index of VxGy for OARs were calculated from dose-volume histograms. Results: Robust-IMPT showed superior dose distributios in the PTV and OARs as compared to plain-IMPT and photon-IMRT. Like plain-IMPT, robust-IMPT were resulted in dose fluctuation around OARs, while better homogeneity and conformity in PTVs and lower mean dose in OARs as compared to photon-IMRT. Conclusion: In consideration with the effective range correction and set up movement using robustness in IMPT plan, the dosimetric uncertainties from plain-IMPT could substantially reduce and suggest more effective solutions than photon-IMRT in prostate cancer treatment.

• Progress in Medical Physics
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• v.21 no.2
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• pp.165-173
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• 2010

In this paper, we evaluated the performance of 3D CRT, IMRT and three kind of RA plannings to investigate the clinical effect of RA with liver cancer case. The patient undergoing liver cancer of small volume and somewhat constant motion were selected. We performed 3D CRT, IMRT and RA plannings such as 2RA, limited triple arcs (3RA) and 3MRA with Eclipse version 8.6.15. The same dose volume objectives were defined for only CTV, PTV and body except heart, liver and partial body in IMRT and RA plannings. The steepness of dose gradient around tumor was determined by the Normal Tissue Objective function with the same parameters in place of respective definitions of dose volume objectives for the normal organs. The approach between the defined dose constraints and the practical DVH of CTV, PTV and Body was the best in 3MRA and the worst in IMRT. The DVHs were almost the same among RAs. Plans were evaluated using Conformity Index (CI), Homogeneity Index (HI) and Quality of coverage (QoC) by RTOG after prescription with dose level surrounding 98% of PTV in the respective plans. As a result, 3MRA planning showed the better favorable indices than that of the others and achieved the lowest MUs. In this study, RA planning is a technique that is possible to obtain the faster and better dose distribution than 3D CRT or IMRT techniques. Our result suggest that 3MRA planning is able to reduce the MUs further, keeping a similar or better targer dose homogeneity, conformity and sparing normal tissue than 2RA or 3RA.

• Radiation Oncology Journal
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• v.29 no.2
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• pp.99-106
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• 2011

Purpose: To analyze our quality assurance (QA) data for intensity modulated radiation therapy (IMRT) according to treatment site and to possibly improve QA for IMRT in Hospital. Materials and Methods: We performed QA on 50 patients (head and neck, 28 patients; Breast, 14 patients; Pelvis, 8 patients) for IMRT. The calculated dose from RTP was compared with the measured value film, gamma index, and ionization chamber for dose measurement in each case. Results: The point dose measurement results in 45 of 50 patients showed good agreement with the calculation dose (${\pm}3%$). The largest error measured thus far has been 3.60%, with a mean of only -0.17% (SD, 2.25%). Each treatment site showed an error rate of -0.13% (SD, 1.93%) for head and neck cases, -0.26% (SD, 2.79%) for breast cases, and 0.24% (SD, 2.44%) for pelvis cases. The gamma index verified with the error rate of head and neck cases (6%), breast (10%), and pelvis (6%), which corresponded to a tolerance of 3 mm (3% for the head and neck, 2%, for the breast 1% for the pelvis, and 0% in the region where the isodose curve was greater than 90%. Conclusion: We recognize the cause of errors for each treatment site of IMRT QA and so we maximize our efforts to reduce error and increase accuracy.

• Applied Biological Chemistry
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• v.43 no.4
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• pp.260-265
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• 2000

To determine the quality change of the irradiated eggs during storage, fresh shell eggs were irradiated using $^{60}Co$ at 0, 1, 5, 10, 30 kGy and stored for 30 days. The york index, color, pH, viscosity, egg weight, and SDS-PAGE profile of the irradiated eggs were examined. During storage, york index values of the irradiated eggs and the control were decreased and the increase of dose decreased yolk index. However, the yolk index values were increased temporarily at 10 kGy and 30 kGy. The yolk color had a bright yellow with increases in dose level and there was no significant change during storage. The albumen viscosities were decreased with increases in dosage and were decreased during storage. Also, the albumen pH values of the irradiated eggs were higher than that of the control and were increased during storage. The weight losses of eggs were increased during storage and there were no significant changes by dose level. SDS-PAGE profile of the egg white proteins of the shell eggs showed the change in molecular weight distribution and had aggregation pattern as well as degradation. CD and fluorescence spectroscopy study showed changes in the secondary and tertiary structure of egg white proteins by ${\gamma}-irradiation$. Therefore, this study clearly indicates that irradiation dose of eggs should be appropriate to prevent the loss of egg qualities.

• Journal of Ecology and Environment
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• v.37 no.4
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• pp.195-200
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• 2014

The chances of accidental exposure are augmented as the application of ionizing radiation increases in various fields. Such accidental exposures may occur at nuclear power plants, laboratories, and hospitals. Cytogenetic assays have been used for estimating radiation dose in the situation of the accidents. The micronucleus assay has several advantages over the other cytogenetic methods as it is simple and fast. The present study aimed at investigation of the micronuclei frequencies in cytokinesis-block cells in human blood lymphocytes after ${\gamma}$-irradiation and at establishment of a standard dose response relationship. The samples of peripheral blood were obtained from 6 different donors aged between 24 and 30 years old. The bloods were irradiated in vitro with 0-5 Gy. A linear quadratic dose-response equation was obtained by scoring the micronuclei in binucleated cells; $y=27.87x^2+46.13x+2.08$ ($r^2=0.99$). Irradiation caused a significant decrease in the nuclear division index. Necrotic and apoptotic cells increased in number after irradiation in a dose-dependent manner. In conclusion, the conventional cytokinesis-block micronucleus assay has proven to be the great technique in biological dosimetry. Dose-response calibration curve derived from CMBN assay could be used to estimate the exposure dose during a radiological emergency.

• Radiation Oncology Journal
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• v.33 no.3
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• pp.242-249
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• 2015

Purpose: The purpose of this study is to compare the dosimetry of electron beam (EB) plans and three-dimensional helical tomotherapy (3DHT) plans for the patients with left-sided breast cancer, who underwent breast conserving surgery. Materials and Methods: We selected total of 15 patients based on the location of tumor, as following subsite: subareolar, upper outer, upper inner, lower lateral, and lower medial quadrants. The clinical target volume (CTV) was defined as the area of architectural distortion surrounded by surgical clip plus 1 cm margin. The conformity index (CI), homogeneity index (HI), quality of coverage (QC) and dose-volume parameters for the CTV, and organ at risk (OAR) were calculated. The following treatment techniques were assessed: single conformal EB plans; 3DHT plans with directional block of left anterior descending artery (LAD); and 3DHT plans with complete block of LAD. Results: 3DHT plans, regardless of type of LAD block, showed significantly better CI, HI, and QC for the CTVs, compared with the EB plans. However, 3DHT plans showed increase in the $V_{1Gy}$ at skin, left lung, and left breast. In terms of LAD, 3DHT plans with complete block of LAD showed extremely low dose, while dose increase in other OARs were observed, when compared with other plans. EB plans showed the worst conformity at upper outer quadrants of tumor bed site. Conclusion: 3DHT plans offer more favorable dose distributions to LAD, as well as improved target coverage in comparison with EB plans.

• Radiation Oncology Journal
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• v.35 no.1
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• pp.90-100
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• 2017

Purpose: To Study the dosimetric advantage of the Jaw tracking technique in intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for Head and Neck Cancers. Materials and Methods: We retrospectively selected 10 previously treated head and neck cancer patients stage (T1/T2, N1, M0) in this study. All the patients were planned for IMRT and VMAT with simultaneous integrated boost technique. IMRT and VMAT plans were performed with jaw tracking (JT) and with static jaw (SJ) technique by keeping the same constraints and priorities for a particular patient. Target conformity, dose to the critical structures and low dose volumes were recorded and analyzed for IMRT and VMAT plans with and without JT for all the patients. Results: The conformity index average of all patients followed by standard deviation (${\bar{x}}{\pm}{\sigma}_{\bar{x}}$) of the JT-IMRT, SJ-IMRT, JT-VMAT, and SJ-VMAT were $1.72{\pm}0.56$, $1.67{\pm}0.57$, $1.83{\pm}0.65$, and $1.85{\pm}0.64$, and homogeneity index were $0.059{\pm}0.05$, $0.064{\pm}0.05$, $0.064{\pm}0.04$, and $0.064{\pm}0.05$. JT-IMRT shows significant mean reduction in right parotid and left parotid shows of 7.64% (p < 0.001) and 7.45% (p < 0.001) compare to SJ-IMRT. JT-IMRT plans also shows considerable dose reduction to thyroid, inferior constrictors, spinal cord and brainstem compared to the SJ-IMRT plans. Conclusion: Significant dose reductions were observed for critical structure in the JT-IMRT compared to SJ-IMRT technique. In JT-VMAT plans dose reduction to the critical structure were not significant compared to the SJ-IMRT due to relatively lesser monitor units.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6187-6192
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• 2014

The use of WBRT(whole brain radiation therapy) has increased due to the increase in the incidence of metastatic brain tumors. The development of radiation therapy techniques is expected to improve the quality of life. The VMAT (Volumetric Modulated Arc Therapy) is an excellent treatment technique that can distinguish the dose in each volume. Therefore, this study compared conventional WBRT and VMAT for hair loss according to the scalp dose using a head phantom. The CI (Conformity Index), HI (Homogeneity Index) and QOC (Quality of Coverage) were measured brain tissue. A 20 percent and 50 percent dose was measured at the scalp, eyeball, lens, and c-spine. Conventional WBRT is excellent at 10 percent of brain tissue. VMAT is far superior at 1000 percent at the other organs. VMAT at the prescribed dose can be used as radiation therapy of metastatic brain tumors with less hair loss.

• Journal of radiological science and technology
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• v.44 no.6
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• pp.663-669
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• 2021

The purpose of this study was to evaluate the usefulness of the rice bolus for upper-lower extremity radiation therapy by Tomotherapy. The computed tomography images were obtained for air, water, and rice bolus. The average and standard deviation of the Hounsfield unit (HU) were measured for image evaluation. The conformity index (CI) and homogeneity index (HI) were calculated for dose distribution of the planning target volume (PTV) which was treated by direct mode with gantry angle (90 and 270 angle). The point dose of a total of ten axial planes was measured to confirm the different regions. The mean of HU was -999.72 ± 0.72 at the air. The water and rice bolus were -0.13 ± 1.65 and -170 ± 27.2, respectively. The CI (HI) of PTV was 0.96 (1.36) at the air. 0.95 (1.04) at the water bolus, and 0.95 (1.04) at the rice bolus. The maximum dose for air was 136 cGy which is about 32% higher than 103 cGy for water and 104 cGy for rice bolus. There was a statistical difference for point dose between air and water including rice bolus (p=0.04), however, no statistical difference between water and rice bolus (p=0.579).The rice bolus phantom for extremities radiation therapy could be not only the optimized dose distribution but also the convenience and equipment safety at Tomotherapy. However, additional research will be necessary to more accurately verify the clinical usefulness of rice bolus phantom due to not enough examination.

• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1041-1047
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• 2023

Temporal bone CT, which is a high-resolution CT, uses a high tube voltage and a thin section thickness, so the scan dose is higher than that of adjacent areas. Accordingly, we applied changes to the reconstruction algorithm among the test conditions to find an algorithm with excellent sensitivity to lesions while reducing the test dose, and investigated its significance and the possibility of providing basic clinical data. As a result, when the tube voltage was lowered to 100 kVp and applied, the dose was reduced by about 35.6%, and when the definition algorithm was applied to the raw data acquired at 100 kVp, the SNR and CNR were excellent, and a statistically significant difference was shown when compared to other algorithms(p<0.05). And as a result of comparing structural similarity, the SSIM index was analyzed as 0.776, 0.813, and 0.741 for each ROI. Therefore, we believe that applying algorithm changes to temporal bone CT scans can partially reduce the dose generated from CT scans and are very meaningful in terms of basic clinical data.