• Progress in Medical Physics
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• v.1 no.1
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• pp.109-122
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• 1990

A method of making inserts for shaped fields in electron beam therapy on the Mevatron KD 67-7467 Linear Acclerator is introduced. The inserts are made from an alloy called Lipowitz metal. These are designed to fit the inside of the standard Siemens cones. Studies have shown that this method does not adversely affect field flatness. However, if the ratio of shaped field to open field is greater than about 70%, the output dose is significantly changed by the inserts. Because the cone ratios for the fields do not follow the open cone ratio curves on the Mevatron KD 67-7467, we separated the cone ratio suggested by Biggs into two parts, the insert ratio and the cone factor. The dosimetry for these shaped beams has been investigated extensively.

• Journal of Radiation Protection and Research
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• v.46 no.3
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• pp.120-126
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• 2021

Background: This paper aims to evaluate the clinical utility and radiation dosimetry, for the mobile X-ray imaging of patients with known or suspected infectious diseases, through the window of an isolation room. The suitability of this technique for imaging coronavirus disease 2019 (COVID-19) patients is of particular focus here, although it is expected to have equal relevance to many infectious respiratory disease outbreaks. Materials and Methods: Two exposure levels were examined, a "typical" mobile exposure of 100 kVp/1.6 mAs and a "high" exposure of 120 kVp/5 mAs. Exposures of an anthropomorphic phantom were made, with and without a glass window present in the beam. The resultant phantom images were provided to experienced radiographers for image quality evaluation, using a Likert scale to rate the anatomical structure visibility. Results and Discussion: The incident air kerma doubled using the high exposure technique, from 29.47 µGy to 67.82 µGy and scattered radiation inside and outside the room increased. Despite an increase in beam energy, high exposure technique images received higher image quality scores than images acquired using lower exposure settings. Conclusion: Increased scattered radiation was very low and can be further mitigated by ensuring surrounding staff are appropriately distanced from both the patient and X-ray tube. Although an increase in incident air kerma was observed, practical advantages in infection control and personal protective equipment conservation were identified. Sites are encouraged to consider the use of this technique where appropriate, following the completion of standard justification practices.

• Journal of Radiation Protection and Research
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• v.21 no.4
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• pp.255-262
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• 1996

This paper describes the results of intercomparison measurements of KAERI reference photon and beta radiation fields between the KAERI and the PNNL(Pacific Northwest National Laboratory), recently performed at KAERI radiation calibration and dosimetry laboratory on the basis of the ANSI N13.11 criteria for personal dosimeter performance test. Each laboratory used her own radiation detectors or measurement devices traceable to her national primary standard in measuring the exposure rates for photon fields, the absorbed dose rates for beta radiation fields. The agreements in reference radiation measurements between two laboratories were found to be less than ${\pm}2.0%$ for photon fields, ${\pm}1.0%$ for beta radiation fields. Therefore, it could be concluded that KAERI reference radiation fields comply well with the international standard and thus can further serve as a national basis for the researches and developments in radiation protection dosimetry in Korea.

• Journal of Radiation Protection and Research
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• v.21 no.2
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• pp.131-138
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• 1996

This paper describes the methods and results of the personnel dosimetry performance tests which were been implemented for the first time in Korea in 1995. Seven categories, except the neutron category prescribed in the ANSI N13.11-1993, were adopted in the test. Fifteen types of dosimeters were participated by fourteen dosimeter processing institutes. A total of 129 dosimeters were selected to test-each type - 15 dosimeters for each of the seven categories and 24 for the controls. A total of 144 radiation categories were employed in the test and a total of 2560 (including 400 controls)dosimeters were submitted-7 categories for each type of the fifteen types dosimeters and 39 categories for the retest. The performance index in each category. sum of the absolute value of the bias and the standard deviation value of the performance quotient. was estimated by the use of delivered and processed dose equivalents according to the standard procedure. The performance in a given category was assessed as acceptable, for the deep and shallow dose equivalents (or the absorbed dose), if the performance index was less than 0.5. The test results showed 54% of the processors passed in the first test, 33% in the retest and 13% in the second retest.

• Progress in Medical Physics
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• v.8 no.2
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• pp.45-57
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• 1997

It is mandatory to measure accurately the dose distribution and the total absorbed dose of fast neutron for putting it to the clinical use. At present the methods of measurement of fast neutron are proposed largely by American Associations of Physicists in Medicine, European Clinical Neutron Dosimetry Group, and International Commission on Radiation Units and Measurements. The complexity of measurement, however, induces the methodological differences between them. In our study, therefore, we tried to establish a unique technique of measurement by means of measuring the emitted doses and the dose distribution of fast neutron beam from neutron therapy machine, and to invent a standard method of measurement adequate to our situation. For measuring the absorbed doses and the dose distribution of fast neutron beam, we used IC-17 and IC-18 ion chambers manufactured by A-150 plastic(tissue-equivalent material), IC-17M ion chamber manufactured by magnesium, TE gas and Ar gas, and RDM 2A electrometer. The magnitude of gamma-contamination intermingled with fast neutron beam was about 13％ at 5cm depth of standard irradiated field, and increased as the depth was increased. At the central axis the maximum dose depth and 50％ dose depth were 1.32cm and 14.8cm, respectively. The surface dose rate was 41.6-54.1％ throughout the entire irradiated fields and increased as the irradiated fields were increased. Beam profile was that the horn effect of about 7.5％ appeared at 2.5cm depth and the flattest at 10cm depth.

• Journal of radiological science and technology
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• v.41 no.6
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• pp.587-594
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• 2018

The purpose of this study was to develop the indirect dosimetry by calculation (IDC) method for diagnostic X-ray equipment. The experiments were performed with inverter type X-ray tubes: Toshiba (E7252X, Japan) and Varian (RAD-14, USA). For the development method, we first applied the standard quality of X-ray beam shown in the TRS457 document, and second, to produce the constants of trendline for the IDC, the total filtration on X-ray beam was subdivided. Third, in order to increase the precision, the energy region was divided into the high energy region and the low energy region and developed by the IDC. In order to verify the IDC, mean dose (mR) values were measured for three Toshiba X-ray tubes and three Varian X-ray tubes at clinical medical institutions and then compared with the IDC on the 2013. As a result, compared with the previous study, the accuracy of the IDC of this study were improved by 2.71% and 9.91% in Toshiba and Varian X-ray tubes, respectively.

• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2698-2703
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• 2024

A bilateral comparison was conducted between the International Atomic Energy Agency (IAEA) and the Korea Research Institute of Standards and Science (KRISS) to measure the absorbed dose to water in accelerator photon beams. KRISS served as a linking laboratory to compare the IAEA standard with the key comparison reference value (KCRV) of the BIPM.RI(I)-K6 program, in which KRISS participated in 2017. Two ionization chambers from the IAEA were used as transfer instruments for the comparison. Both laboratories measured the calibration coefficients of these instruments and calculated the ratios. The ratio of the KRISS standard to the KCRV was applied to obtain the degree of equivalence of the IAEA, along with its uncertainty. The largest deviation of the IAEA measurement from the KCRV was 3.4 mGy/Gy, significantly smaller than the expanded uncertainty of 10.7 mGy/Gy (k = 2, 95% level of confidence). This study demonstrates the equivalence of IAEA's measurement standard for accelerator photon beams to other primary standard dosimetry laboratories. It provides evidence for the satisfactory operation of IAEA's quality management system and enhances the international credibility of the IAEA SSDL network, particularly in high-energy accelerator photon beams from linear accelerators.

• Imaging Science in Dentistry
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• v.40 no.1
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• pp.15-23
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• 2010

Purpose : This study was designed to compare the effective doses from low-dose and standard-dose multi-detector CT (MDCT) scanning protocols and evaluate the image quality and the spatial resolution of the low-dose MDCT protocols for clinical use. Materials and Methods : 6-channel MDCT scanner (Siemens Medical System, Forschheim, Germany), was used for this study. Protocol of the standard-dose MDCT for the orthodontic analysis was 130 kV, 35 mAs, 1.25 mm slice width, 0.8 pitch. Those of the low-dose MDCT for orthodontic analysis and orthodontic surgery were 110 kV, 30 mAs, 1.25 mm slice width, 0.85 pitch and 110 kV, 45 mAs, 2.5 mm slice width, 0.85 pitch. Thermoluminescent dosimeters (TLDs) were placed at 31 sites throughout the levels of adult female ART head and neck phantom. Effective doses were calculated according to ICRP 1990 and 2007 recommendations. A formalin-fixed cadaver and AAPM CT performance phantom were scanned for the evaluation of subjective image quality and spatial resolution. Results : Effective doses in ${\mu}Sv$ ($E_{2007}$) were 699.1, 429.4 and 603.1 for standard-dose CT of orthodontic treatment, low-dose CT of orthodontic analysis, and low-dose CT of orthodontic surgery, respectively. The image quality from the low-dose protocol were not worse than those from the standard-dose protocol. The spatial resolutions of both standard-dose and low-dose CT images were acceptable. Conclusion : From the above results, it can be concluded that the low-dose MDCT protocol is preferable in obtaining CT images for orthodontic analysis and orthodontic surgery.

• Journal of the Korean Society of Radiology
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• v.4 no.4
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• pp.29-32
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• 2010

The neutron capture cross section of $^{197}Au$ has been measured relative to the $^{10}B(n,{\gamma})$ standard cross section by the neutron time-of-flight(TOF) method using a 46-MeV electron linear accelerator(linac) at the Research Reactor Institute, Kyoto University(KURRI). In order to experimentally prove the result obtained, the supplementary cross section measurement has been made from 0.1 eV to 10 keV using the Kyoto University Lead slowing-down spectrometer (KULS) coupling to the linac. The relative measurement by the TOF method has been normalized to the reference value(24.5 b) at 1 eV. The evaluated capture cross sections in JENDL/D-99 Dosimetry have been compared with the current measurements by the KULS experiments.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.68-73
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• 2002

In standard teletherapy, a treatment plan is generated with the aid of a treatment planning system, but it is common to perform an independent monitor unit verification calculation (MUVC). In exact analogy, we propose and demonstrate that a simple and accurate MUVC in Intensity Modulated Radiotherapy (IMRT) is possible. We introduce a concept of Modified Clarkson Integration (MCI). In MCI, we exploit the rotational symmetry of scattering to simplify the dose calculation. For dose calculation along a central axis (CAX), we first replace the incident IMRT fluence by an azimuthally averaged fluence. Second, the Clarkson Integration is carried over annular sectors instead of over pie sectors. We wrote a computer code, implementing the MCI technique, in order to perform a MUVC for IMRT purposes. We applied the code to IMRT plans generated by CORVUS. The input to the code consists of CORVUS plan data (e.g., DMLC files, jaw settings, MU for each IMRT field, depth to isocenter for each IMRT field), and the output is dose contribution by individual IMRT field to the isocenter. The code uses measured beam data for Sc, Sp, TPR, (D/Mu)$\_$ref/ and includes effects from MLC transmission, and radiation field offset. On a 266 MHZ desktop computer, the code takes less than 15 sec to calculate a dose. The doses calculated with MCI algorithm agreed within +/- 3% with the doses calculated by CORVUS, which uses a 1cm x 1cm pencil beam in dose calculation. In the present version of MCI, skin contour variations and inhomogeneities were neglected.