• Radiation Oncology Journal
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• v.7 no.1
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• pp.93-100
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• 1989

Several combinations of measuring devices and phantoms were studied to measure electron beams. Silicon Pmt junction diode was used to find the dependence of depth dose profile on field size on axis of electron beam Depths of 50, 80 and $90\%$ doses increased with the field size for small fields. For some larger fields, they were nearly constant. The smallest of field sizes over which the parameters were constant was enlarged with increase of the energy of electron beams. Depth dose distributions on axis of electron beam of $10\times10cm^2$ field were studied with several combinations of measuring devices and phantoms. Cylindrical ion chamber could not be used for measurement of surface dose, and was not convenient for measurement of near surface region of 6MeV electron. With some exceptions, parameters agreed well with those studied by different devices and phantoms. Surface dose in some energies showed $4\%$ difference between maximum and minimum. For 18MeV, depths of 80 and $90\%$ doses were considerably shallower by film than by others. Parallel-plate ion chamber with polystyrene phamtom and silicon PN junction would be recommended for measurement of central axis depth dose of electron beams with considerably large field size. It is desirable not to use cylindrical ion chamber for the purpose of measurement of surface dose or near surface region for lower energy electron beam. It is questionable that film would be recommended for measurement of dose distribution of electron with high energy like as 18MeV.

• Journal of Radiation Protection and Research
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• v.36 no.2
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• pp.86-92
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• 2011

This study used the optically stimulated luminescence dosimeters (OSLDs), recently, received the revaluation of usefulness in vivo dosimetry, and the diode detecters to measure the skin dose of patient with the rectal cancer. The measurements of dose delivered were compared with the planned dose from the treatment planning system (TPS). We evaluated the clinical application of OSDs in radiotherapy. We measured the calibration factor of OSLDs and used the percent depth dose to verified, also, we created the three point of surface by ten patients of rectal cancer to measured. The calibration factors of OSLD was 1.17 for 6 MV X-ray and 1.28 for 10 MV X-ray, demonstrating the energy dependency of X-ray beams. Comparison of surface dose measurement using the OSLDs and diode detectors with the planned dose from the TPS, The skin dose of patient was increased 1.16 ~ 2.83% for diode detectors, 1.36 ~ 2.17% for OSLDs. Especially, the difference between planned dose and the delivery dose was increased in the perineum, a skin of intense flexure region, and the OSLDs as a result of close spacing of measuring a variate showed a steady dose verification than the diode detecters. Therefore, on behalf of the ionization chamber and diode detecters, OSLDs could be applied clinically in the verification of radiation dose error and in vivo dosimety. The research on the dose verification of the rectal cancer in the around perineal, a surface of intense flexure region, suggest continue to be.

• Journal of radiological science and technology
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• v.33 no.2
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• pp.149-154
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• 2010

Exposed doses to the patient's caregiver and their house due to the 131I from patients discharged from the hospital were measured using OSL dosimeters. Usually, 3.37-5.55 GBq (100-150 mCi) of $^{131}I$ administrated patients are discharged from the hospital after 3 or 4 days of hospitalization in Korea. In addition, after 5 to 8 days, the accumulated doses of the patient's caregiver and house after hospitalization of the patient were measured using OSL dosimeters. The results of the measured average accumulated doses were 0.1 mSv, which is 10% of 1 mSv, the public dose limit in the Korean Atomic Energy Law. And it's standard deviation was 0.087 mSv. Based on the results of this study, we anticipate that we could assure the compliance of the regulation requirement 5 mSv of MEST (Ministry of Education, Science and Technology) Notice No. 2008-45 for the patient's caregiver or family, even if we reduce the 3-4 days of hospitalization to 1-2 days or less.

• Journal of Radiation Protection and Research
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• v.38 no.1
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• pp.44-51
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• 2013

ICRP recommended that cosmic ray exposure to the pilot and cabin crew would be considered as an occupational exposure due to their relatively high exposure. Since 2012 with the Act No. 10908 (Natural radiation management), the guideline of cosmic ray exposure to the pilot was established in Korea. The applicability of the solid-state nuclear track detector for personal dose assessment of pilot and cabin crew was evaluated. Dose linearity and angle dependence of dosimeters to the neutron were evaluated by $^{252}Cf$ neutron emitting source. The track density has a good agreement with the dose ($r^2$=0.99) and highly dependent on the degree of an angular of the dosimeter to the neutron source. In addition, the dosimeters (SSNTD) were exposed to cosmic ray in an aircraft during its cruising for more than two months in collaboration with Airline Pilots Association of Korea. Although the correlation between the track density from aircraft cruising altitude and expected neutron dose is low, however RSNS dosimeter could be used for personal neutron dosimeter. For application of RSNS as a personal dosimeter for pilot and cabin crew, additional studies are required.

• Korean Journal of Digital Imaging in Medicine
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• v.14 no.2
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• pp.39-46
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• 2012

Purpose : The purpose of this study was to reduce Entrance Surface Dose and maintain image quality by changing Source to Image receptor Distance. And we'd like to compare ESD on this study to DRLs in other contries. Materials and Methods : We used indirect DR system(Definium 8000, General Electric, USA)and phantom(ART-200X, Flukebiomedical, USA),glass dosimeters(GD-352M, Asahi Techno Glass, Japan)for this study. The imagies were obtained throuh 80kVp fixed, and different tube currents using AEC mode in $16{\times}16$(inch) field size and changing Source to Image receptor Distance from 100 cm to 130 cm per 10 cm unit. The phantom with attaching 5 glass dosimeters on abdomonal skin was set at supine and erect position as a anterioposterial projection on detector For measuring Entrance Surface Dose. Image analysis was conducted by histograms of Image J(1.46r) which was given from National Institutes of Health(NIH). Results : Due to inverse square law of distance, the tube currents were increasing 42.6 % in supine position and 32.6 % in erect position according to the change of Source to Image receptor Distance. While Entrance Surface Doses were rapidly decreasing 14.2 % in supine position and 29.4 % in erect position according to the change of Source to Image receptor Distance. As the results of histogram using Image J, pixel mean values from 100 cm to 110 cm, 120 cm and 130 cm were decreasing each 1.4%, 2.5%, 2.7%, 4.5%, 2.2 %, 5.8 % in supine, erect position. While standard deviations from 100 cm to 110 cm, 120 cm and 130 cm were increasing each 1.4 %, 2.5 %, 2.5 %, 4.0 %, 2.0 %, 4.9 % Consequently, there are no significant differences in abdomen images taken. Conclusion: As the results described above, we strongly recommend using long Sourceto Image receptor Distance than 100cm that we have been using. So, we should deliver less Entrance Surface Dose to the patients while maintaining image quality in abdomen radiography.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2379-2386
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• 2020

This paper presents the results of the first intercomparison exercise performed by the Korea retrospective dosimetry (KREDOS) working group using electron paramagnetic resonance (EPR) spectroscopy. The intercomparison employed the alanine dosimeter, which is commonly used as the standard dosimeter in EPR methods. Four laboratories participated in the dose assessment of blind samples, and one laboratory carried out irradiation of blind samples. Two types of alanine dosimeters (Bruker and Magnettech) with different geometries were used. Both dosimeters were blindly irradiated at three dose levels (0.60, 2.70, and 8.00 Gy) and four samples per dose were distributed to the participating laboratories. Assessments of blind doses by the laboratories were performed using their own measurement protocols. One laboratory did not participate in the measurements of Magnettech alanine dosimeter samples. Intercomparison results were analyzed by calculating the relative bias, E_n value, and z-score. The results reported by participating laboratories were overall satisfactory for doses of 2.70 and 8.00 Gy but were considerably overestimated with a relative bias range of 10-95% for 0.60 Gy, which is lower than the minimum detectable dose (MDD) of the alanine dosimeter. After the first intercomparison, participating laboratories are working to improve their alanine-EPR dosimetry systems through continuous meetings and are preparing a second intercomparison exercise for other materials.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.333-338
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• 2019

In the field of radiotherapy, the Quality Assurance(QA) procedure to verify the safety of treatment is considered to be very important. However, due to various problems of the conventional dosimeters used for the QA, researches on these dosimeters have been actively carried out to replace them. In this study, to maximize the sensitivity by visible light(VL) emitted from phosphors, blended hybrid sensors were fabricated by blending various weight percent(wt%) of $Gd_2O_2S:Tb$ which is a phosphor with excellent fluorescence efficiency into $PbI_2$. Then, the electrical properties to high energy radiation from the blended sensors and the pure $PbI_2$ sensor were compared and evaluated. As a result of the sensitivity evaluation, the sensor of 3wt% showed the highest value with more than 40% difference from the other sensors, and gradual decreasing in sensitivity was observed with increasing wt% except for the sensor of 3wt%. Also, in the reproducibility evaluation, the pure $PbI_2$ sensor exhibited a large variation in coefficient of variation(CV)>0.015, while all the blended sensors showed CV<0.015.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.9
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• pp.831-840
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• 2013

The noise levels of workers in tunnel sites are likely to be high because tunneling work places are confined space. However, research on the noise exposure levels of tunneling workers have not been performed intensively due to restricted accessibility to tunnel construction sites. The aim of this study is to evaluate the noise exposure levels for workers engaged in tunneling work sites. Noise dosimeters were used for monitoring workers' noise exposure level in 5 tunneling work sites in accordance with the Notification of the Ministry of Labor. Among 5 tunneling work sites, 4 of them used NATM tunneling method and 1 work site used shield TBM tunneling method. The average noise exposure levels of NATM tunneling workers was 81.1 dB(A) and 15.4 % of the workers' noise level were exposed more than 90 dB(A) which is the exposure limit value. In Shield TBM tunneling method, 4.3 % of the workers were exposed more than 90 dB(A) of noise level, the average noise exposure levels of TBM tunneling workers was 84.1 dB(A).

• Progress in Medical Physics
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• v.31 no.2
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• pp.20-28
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• 2020

Purpose: The objective of this study is to perform Postal dosimetry audits for medical linear accelerators in radiation therapy institutions using glass dosimeters and Gafchromic film reading systems and postal dosimetry audit procedures, and to evaluate radiation therapy doses and mechanical accuracy in medical institutions. Methods: Photon output measured and analyzed using a standard phantom for measuring photon output dose using a glass dosimeter for medical linear accelerators. Mechanical accuracy was measured and analyzed using software for film measurement. Results: Measurement and analysis of photon beam output dose using a standard phantom glass dosimeter for photon beam output dose measurement was completed. All tolerance doses were within 5%. Mechanical accuracy measurement and analysis using a standard phantom for verifying the mechanical accuracy of linear accelerator (LINAC) using a Gafchromic film were completed, and all results were shown within tolerances (2 mm or less). Conclusions: In this study, Postal dosimetry audits were performed on the output dose and mechanical accuracy of photon beams (207 beams) for 106 LINACs from 48 institutions. As a result of corrective action and re-execution, it was confirmed that all engines met the acceptable standard within 2 mm in the linear accelerator.

• Progress in Medical Physics
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• v.1 no.1
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• pp.97-107
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• 1990

A method of detecting charged particles in an allyl diglycol carbonate material (PN-3) which is available, amorphous, optically clear and thermoset plastic in which nuclear particle tracks could be revealed by etching in hot NaOH solutions, has been investigated. It has been applied to the study of alpha particle tracks over an energy range of 3.17～5.49 MeV which has been obtained after having passed through several sheets of polycarbonate. The dose equivalent rate of the alpha source was calculated and the spark chamber was used in order to measure the range of alpha particles after having passed through different number of absorbers. The etching characteristics and the detection response of PN-3 have been studied as a funcion of lengths of etched tracks against the parameters of energies and of the track etching rate(V$_{T}$). The investigation of the etching process for alpha particles in the PN-3 provided the most interesting results.s.