• Progress in Medical Physics
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• v.6 no.2
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• pp.41-50
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• 1995

The absorbed dose and contaminant electron distribution of therapeutic X-ray beam (15MV photon) was studied with a half blocked beams of 30$\times$30$\textrm{cm}^2$ and field size ranging from 5$\times$5 to 30$\times$30$\textrm{cm}^2$. For a 15MV photon beam energy, the value of the depth of dose maximum, d$_{max}$, gradually decrease with increasing field size from 5$\times$5 to 30$\times$30$\textrm{cm}^2$ due to mainly by contaminant electrons which are produced in the flattening filter and scattered by collimator jaws, tray holder〔Lucite〕, blocking block and air. The results suggest that separate dosimetry data should be kept for blocked and unblocked field. The inherence of the contaminant electrons to the open field depth of maximum dose can lead to mistaken results if attenuation measurements are made at that depth. A nurmerous contaminant electrons mainly were distributed as shape of corn in the central photon beam and their path length in the water were shorter than 30mm because of the electrons energy having around 6MeV. These results clearly appears that the substraction of scattered electrons (electrons and positrons) from the total depth dose curve not only lowers the absolute dose in the bulidup region and surface dose, it also causes a shift of d$_{max}$ to a deeper depth. In the terapeutic high energy photon beam, the absorbed dose near the buildup region is the combined result of incident contaminant electrons and phantom generated electronsrons.

• Radiation Oncology Journal
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• v.16 no.3
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• pp.337-345
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• 1998

Purpose : To obtain the uniform dose at limited depth to entire surface of the body, the dose characteristics of degraded electron beam of the large target-skin distance and the dose distribution of the six-dual electron fields were investigated Materials and Method : The experimental dose distributions included the depth dose curve, spatial dose and attenuated electron beam were determined with 300 cm of target-skin distance (TSD) and full collimator size (35*35 $cm^2$ on TSD 100 cm) in 4 MeV electron beam energy. Actual collimated field size of 105 cm * 105 cm at the distance of 300 cm could include entire hemibody. A patient was standing on step board with hands up and holding the pole to stabilize his/her positions for the six-dual fields technique. As a scatter-degrader, 0.5 cm of acrylic plate was inserted at 20 cm from the body surface on the electron beam path to induce ray scattering and to increase the skin dose. Results : The full width at half maximum(FWHM) of dose profile was 130 cm in large field of 105*105 $cm^2$ The width of $100\pm10\%$ of the resultant dose from two adjacent fields which were separated at 25 cm from field edge for obtaining the dose unifomity was extended to 186 cm. The depth of maximum dose lies at 5 mm and the 80$\%$ depth dose lies between 7 and 8 mm for the degraded electron beam by using the 0.5 cm thickness of acrylic absorber. Total skin electron beam irradiation (TSEBI) was carried out using the six dual fields has been developed at Stanford University. The dose distribution in TSEBI showed relatively uniform around the flat region of skin except the protruding and deeply curvatured portion of the body, which showed excess of dose at the former and less dose at the latter. Conclusion : The percent depth dose, profile curves and superimposed dose distribution were investigated using the degraded electron beam through the beam absorber. The dose distribution obtained by experiments of TSEBI showed within$\pm10\%$ difference except the protruding area of skin which needs a shield and deeply curvatured region of skin which needs boosting dose.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.13
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• pp.5259-5264
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• 2014

Background: CT based brachytherapy allows 3-dimensional (3D) assessment of organs at risk (OAR) doses with dose volume histograms (DVHs). The purpose of this study was to compare computed tomography (CT) based volumetric calculations and International Commission on Radiation Units and Measurements (ICRU) reference-point estimates of radiation doses to the bladder and rectum in patients with carcinoma of the cervix treated with high-dose-rate (HDR) intracavitary brachytherapy (ICBT). Materials and Methods: Between March 2011 and May 2012, 20 patients were treated with 55 fractions of brachytherapy using tandem and ovoids and underwent post-implant CT scans. The external beam radiotherapy (EBRT) dose was 48.6Gy in 27 fractions. HDR brachytherapy was delivered to a dose of 21 Gy in three fractions. The ICRU bladder and rectum point doses along with 4 additional rectal points were recorded. The maximum dose ($D_{Max}$) to rectum was the highest recorded dose at one of these five points. Using the HDRplus 2.6 brachyhtherapy treatment planning system, the bladder and rectum were retrospectively contoured on the 55 CT datasets. The DVHs for rectum and bladder were calculated and the minimum doses to the highest irradiated 2cc area of rectum and bladder were recorded ($D_{2cc}$) for all individual fractions. The mean $D_{2cc}$ of rectum was compared to the means of ICRU rectal point and rectal $D_{Max}$ using the Student's t-test. The mean $D_{2cc}$ of bladder was compared with the mean ICRU bladder point using the same statistical test. The total dose, combining EBRT and HDR brachytherapy, were biologically normalized to the conventional 2 Gy/fraction using the linear-quadratic model. (${\alpha}/{\beta}$ value of 10 Gy for target, 3 Gy for organs at risk). Results: The total prescribed dose was $77.5Gy{\alpha}/{\beta}10$. The mean dose to the rectum was $4.58{\pm}1.22Gy$ for $D_{2cc}$, $3.76{\pm}0.65Gy$ at $D_{ICRU}$ and $4.75{\pm}1.01Gy$ at $D_{Max}$. The mean rectal $D_{2cc}$ dose differed significantly from the mean dose calculated at the ICRU reference point (p<0.005); the mean difference was 0.82 Gy (0.48-1.19Gy). The mean EQD2 was $68.52{\pm}7.24Gy_{{\alpha}/{\beta}3}$ for $D_{2cc}$, $61.71{\pm}2.77Gy_{{\alpha}/{\beta}3}$ at $D_{ICRU}$ and $69.24{\pm}6.02Gy_{{\alpha}/{\beta}3}$ at $D_{Max}$. The mean ratio of $D_{2cc}$ rectum to $D_{ICRU}$ rectum was 1.25 and the mean ratio of $D_{2cc}$ rectum to $D_{Max}$ rectum was 0.98 for all individual fractions. The mean dose to the bladder was $6.00{\pm}1.90Gy$ for $D_{2cc}$ and $5.10{\pm}2.03Gy$ at $D_{ICRU}$. However, the mean $D_{2cc}$ dose did not differ significantly from the mean dose calculated at the ICRU reference point (p=0.307); the mean difference was 0.90 Gy (0.49-1.25Gy). The mean EQD2 was $81.85{\pm}13.03Gy_{{\alpha}/{\beta}3}$ for $D_{2cc}$ and $74.11{\pm}19.39Gy_{{\alpha}/{\beta}3}$ at $D_{ICRU}$. The mean ratio of $D_{2cc}$ bladder to $D_{ICRU}$ bladder was 1.24. In the majority of applications, the maximum dose point was not the ICRU point. On average, the rectum received 77% and bladder received 92% of the prescribed dose. Conclusions: OARs doses assessed by DVH criteria were higher than ICRU point doses. Our data suggest that the estimated dose to the ICRU bladder point may be a reasonable surrogate for the $D_{2cc}$ and rectal $D_{Max}$ for $D_{2cc}$. However, the dose to the ICRU rectal point does not appear to be a reasonable surrogate for the $D_{2cc}$.

• Radiation Oncology Journal
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• v.13 no.4
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• pp.349-357
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• 1995

Purpose : To analyze survival rate and late rectal and bladder complication for patients with stage I and II carcinoma of uterine cervix treated by radiation alone or combined with chemotherapy Materials and Methods : Between November 1984 and December 1993, 127 patients with stage I and II carcinoma of uterine cervix treated by radiation alone or combined therapy of radiation and chemotherapy. Retrospective analysis for survival rate was carried out on eligible 107 patients and review for complication was possible in 91 patients. The median follow-up was 47 months (range 3-118) and the median age of patiens was 56 years (range 31-76). 26 patients were stage IB by FIGO classification, 40 were stage IIA and 41 were stage IIB. 86 cases were treated by radiation alone and 21 were treated by radiation and chemotherapy. 101 patients were treated with intracavitary radiation therapy (ICRT), of these, 80 were received low dose rate (LDR) ICRT and 21 were received high dose rate (HDR) ICRT. Of the patients who received LDR ICRT, 63 were treated by 1 intracavitary insertion and 17 were underwent 2 insertions And we evaluated the external radiation dose and midline shield. Results : Actuarial survival rate at 5 years was $92{\%}$ for stage IB, $75{\%}$ for stage IIA, $53{\%}$ for stage IIB and $69{\%}$ in all patients Grade 1 rectal complications were developed in 20 cases ($22{\%}$), grade 2 were in 22 cases ($24{\%}$). 22 cases ($24{\%}$) of grade 1 urinary complications and 17 cases ($19{\%}$) of grade 2 urinary complications were observed But no patient had severe complications that needed surgical management or admission care. Maximum bladder dose for the group of patients with urinary complications was higher than that for the patients without urinary complications (7608 cGy v 6960cGy. p<0.01) Maximum rectal dose for the group of patients with rectal complications was higher than that for the patients without rectal complications (7041cGy v 6269cGy, p<0.01). While there was no significant difference for survival rate or bladder complication incidence as a function of dose to whole pelvis, Grade 2 rectal complication incidence was significantly lower for the patients receiving less than 4500cGy ($6.3{\%}$ v $25.5{\%}$, p<0.05). There was no significant differance between HDR ICRT group and LDR ICRT group for survival rate according to stage, on the other hand complication incidence was higher in the HDR group than LDR group, This was maybe due to different prescription doses between HDR group and LDR group. Midline shield neither improved survival rate nor decreased complication rate. The number of insertion in LDR ICRT group did not affect on survival and compication rate. Conclusion : In stage I and II carcinoma of uterine cervix there was no significant differance for 5 year survival rate by radiation therapy technique. Rectal complication incidence was as a function of dose to whole pelvis and there were positive correlations of maximum dose of rectum and bladder and each complication incidence. So we recommand whole pelvis dose less than 4500cGy and maximum dose of rectum and bladder as low as possible.

• Radiation Oncology Journal
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• v.1 no.1
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• pp.29-36
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• 1983

The treatment of tumors along curved surfaces with stationary electron beams using cone collimation may lead to non-uniform dose distributions due to a varying air gap between the cone surface and patient. For large tumors, more than one port may have to be used in irradiation of the chest wall, often leading to regions of high or low dose at the junction of the adjacent ports. Electron-beam arc therapy may elimination many of these fixed port problems. When treating breast tumors with electrons, the energy of the internal mammary port is usually higher than that of the chest wall port. Bolus is used to increase the skin dose or limit the range of the electrons. We invertiaged the effect of various arc beam parameters in the isodose distributions, and combined into a single arc port for adjacent fixed ports of different electron beam eneries. The higher fixed port energy would be used as the arc beam energy while the beam penetration in the lower energy region would be controlled by a proper thickness of bolus. We obtained the results of following: 1. It is more uniform dose distribution of electron to use rotation than stationary irradiation. 2. Increasing isocenter depth on arc irradiation, increased depth of maximum dose, reduction in surface dose and an increasing penetration of the linear portion of the curve. 3. The deeper penetration of the depth dose curve and higher X-ray background for the smaller field sized. 4. If the isocenter depth increase, the field effect is small. 5. The decreasing arc beam penetration with decreasing isocenter depth and the isocenter depth effect appears at a greater depth as the energy increases. 6. The addition of bolus produces a shift in the penetration that is the same for all depths leaving the shape of the curves unchanged. 7. Lead strips 5 mm thick were placed at both ends of the arc to produce a rapid dose drop-off.

• Journal of Korean Neurosurgical Society
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• v.30 no.5
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• pp.561-566
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• 2001

Objective : The purpose of this study are to evaluate the effectiveness of Gamma Knife radiosurgery(GKS) as a treatment of craniopharyngioma and to investigate the proper dose planning technique in GKS for craniopharyngioma. Method : Between May 1992 and March 1999, seven Gamma Knife radiosurgical procedures were done for residual tumor mass of 6 patients with craniopharyngioma after microsurgical resection. Conventional radiation therapy was not performed. In this study, their clinical, radiological and radiosurgical data were analyzed and the radiation dosage to the optic pathway, hypothalamus, pituitary stalk, and cavernous sinus were calculated and correlation with clinical outcome was evaluated. The mean follow-up period was 33.5 months(12.3-55.2 months). Result : The mean tumor volume was 4.4cc(0.4-18.0cc) and the maximum radiation dose ranged from 14 to 32 Gy(mean 20.9Gy). The radiation was given with isodose curve, 50-90% and the marginal dose varied within 8-22.4Gy(mean 12.7Gy). The mean number of isocenter was 4.3(1-12). The tumor was well controlled in all cases. In 5 of 7 cases, the size of tumor decreased to 10-50% of pre-GKS volume and remaining two showed no volume change. The mean dose to optic pathway was 5.7Gy(5.1-11.2Gy) and there were no complications. Conclusion : GKS seems to be effective for control of craniopharyngioma as an adjuvant treatment after microsurgical resection and even suboptimal dose for tumor margin is considered to be enough for tumor control. It is safe with careful dose planning to protect surrounding important structures, especially optic pathway. We believe conventional radiation therapy should be avoided because it has limitation for dose planning of additional treatments such as radiosurgery or intracystic instillation of radioisotope in case of recurrence.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2624-2628
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• 2011

Exposed dose of a patient was measured by Radiophotoluminescent Glass Rod Detector with a use of a panorama graphic device in dental examination. The effect of exposed dose in optic lens was measured by comparing the different materials of the glasses. Depending on the dental location, the exposed dose distribution was 82.4~2,340uSv. It showed that the maximum difference in dose distribution was over 300%. Thus, when manufacturing the devices, it seemed to require shortening the pre-heat time and additional shielding in order to control the diagnosis and exposed dose. The measurement data of the exposed dose in optic lens was increased 20~75uSv per each test when compared putting on glasses with not wearing. As a result, taking off the glasses is recommended to improve efficiency of the test and minimize the exposed dose during dental panorama graphic examinations.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.383-387
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• 2015

This study investigated the size specific dose estimates of difference localizer on pediatric CT image. Seventy one cases of pediatric abdomen-pelvic CT (M:F=36:35) were included in this study. Anterior-posterior and lateral diameters were measured in axial CT images. Conversion factors from American Association of Physicists in Medicine (AAPM) report 204 were obtained for effective diameter to determine size specific dose estimate (SSDE) from the CT dose index volume (CTDIvol) recorded from the dose reports. For the localizer of mid-slice SSDE was 107.63% higher than CTDIvol and that of xiphoid-process slices SSDE was higher than 92.91%. The maximum error of iliac crest slices, xiphoid process slices and femur head slices between mid-slices were 7.48%, 17.81% and 14.04%. In conclusion, despite the SSDE of difference localizer has large number of errors, SSDE should be regarded as the primary evaluation tool of the patient radiation in pediatric CT for evaluation.

• Journal of Gastric Cancer
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• v.21 no.4
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• pp.418-425
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• 2021

Purpose: We designed a new regimen by combining intraperitoneal (IP) paclitaxel (PTX) with systemic S-1 plus oxaliplatin (SOX) for the treatment of advanced gastric cancer with peritoneal metastasis. This dose-escalation study aimed to determine the maximum tolerated dose (MTD) and recommended dose (RD) of IP PTX administered weekly to patients. Materials and Methods: Eight cycles of IP PTX plus SOX regimen were administered to the patients. S-1 was administered orally twice daily at a dose of 80 mg/m²/day for 14 consecutive days, followed by 7 days of rest. Intravenous oxaliplatin was administered at a fixed dose of 100 mg/m² on day 1, while IP PTX was administered on days 1 and 8. The initial dose of IP PTX was 40 mg/m², and the dose escalation was set in units of 20 mg/m² up to 80 mg/m². Dose-limiting toxicities (DLTs) were defined as grade 3 non-hematologic toxicities, grade 4 leukopenia, grade 3 febrile neutropenia, and grade 3 thrombocytopenia. Results: Nine patients were included in the study. No DLTs were observed in any of the enrolled patients. Therefore, the MTD was not reached, and the RD of IP PTX was determined to be 80 mg/m². Four patients (44%) showed a decreased peritoneal cancer index score on second-look laparoscopic examination. Conclusions: The present study determined the dose for further clinical trials of IP PTX to be 80 mg/m², when combined with a systemic SOX regimen.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1935-1945
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• 2023

The radiological safety of workers in a newly developed microwave-based spent resin treatment facility was assessed based on work location and operational scenarios. The results show that the remote-operation room worker was exposed to maximum annual dose of 3.19E+00 mSv, which is 15.9% of the dose limit, thereby confirming radiological safety. Inside the pathway, annual doses in the range of 7.87E-02-2.07E-01 mSv were measured initially at the mock-up tank and later at the point between the spent resin separation and treatment parts. The dose of emergency maintenance workers was below the dose limit (4.08E-03-4.99E+00 mSv); however, before treatment (separation and microwave), the dose of maintenance and repair workers exceeded the dose limit. The doses of the effluent removal workers at the zeolite and activated carbon storage tank and spent resin storage tank were the lowest at 2.79E-01-2.87E-01 mSv and 9.27E-01 mSv in "1 h" and "4-5 h of operation", respectively. The immediately lower and upper layers of the facility room exhibited the highest annual doses of 1.84E+00 and 3.22E+00 mSv, respectively. Through this study, a scenario that can minimize the dose considering the movement of spent resin through the facility can be developed.