• Journal of radiological science and technology
• /
• v.35 no.2
• /
• pp.119-124
• /
• 2012

Recently, Glass Dosimeter (GD) with thermoluminescent Dosimeter (TLD) are comprehensively used to measure absorbed dose from diagnostic field to therapy field that means from low energy field to high energy field. However, such studies about dose characteristics of GD, such as reproducibility and energy dependency, are mostly results in high energy field. Because characteristic study for measurement devices of radiation dose and radiation detector is performed using 137Cs and 60Co which emit high energy radiations. Thus, this study was evaluated the linearity according to Piranha dose which measured by changing tube voltage (50kV, 80kV and 100kV which are low energy radiations), reproducibility and reproducibility according to delay time using GD. Measurement of radiation dose is performed using internal detector of Piranha 657 which is multi-function QA device (RTI Electronic, Sweden). Condition of measurement was 25mA, 0.02sec, 2.5mAs, SSD of 100 cm and exposure area with $10{\times}10cm^2$. As above method, GD was exposed to radiation. Sixty GDs were divided into three groups (50kV, 80kV, 100kV), then measured. In this study, GD was indicated the linearity in low energy field as high energy existing reported results. The reproducibility and reproducibility according to delay time were acceptable. In this study, we could know that GD can be used to not only measure the high energy field but also low energy field.

• Progress in Medical Physics
• /
• v.24 no.4
• /
• pp.315-322
• /
• 2013

The aim of this work is to verify the self-quality assurances in medical institutions in Korea through the external audits by the group of experts and have a mutual discussion of the systematic problems. In order to validate the external audits 30 of 80 medical institutions across the nation were picked out considering the regional distribution and the final 25 institutions applied voluntarily to take part in this work. The basic rules were setup that any information of the participants be kept secrete and the measurements be performed with the dosimetry system already verified through intercomparision. The outputs for 2 or more photon beams, the accuracy of gantry rotation and collimator rotation and the poistional accuracy of MLC movement were measured. The findings for the output measurement showed the differences of -0.8%~4.5%, -0.79%~3.01%, and -0.7%~0.07% with respect to that of the verified dosimetry system for the 6MV, 10MV, and 15MV, respectively. For the reference absorbed dose 8 (16%) of 50 photon beams in 25 medical institutions differed 2.0% or greater from the reference value. The coincidences of Field size with x-ray beam and radiation isocenters of Gantry roration and collimator rotation gave the results of within ${\pm}2$ mm for every institute except 2 institutions. The positional accuracy of MLC movement agreed to within ${\pm}1$ mm for every institute. For the beam qualities of 6 MV photon beams kQ values showed the distribution within 0.4% between maximum and minimum. For the protocols 21 institutions (84%) used absorbed dose to water based protocol while 4 insitutions (16%) used air kerma based one. 22 institutions employed the SSD technique while 3 institutions did the SAD one. External audit plays an important role in discovering the systematic problems of self-performing Quality Assurances and having in depth discussion for mutual complementation. Training experts of international level as well as national support system are required so that both the group of experts of medical physicists and government laboratory could perform together periodical and constant external audits.

• Journal of Radiation Protection and Research
• /
• v.40 no.2
• /
• pp.118-123
• /
• 2015

The frequency of diagnostic radiation examinations in medical institutions has recently increased to 220 million cases in 2011, and the annual exposure dose per capita was 1.4 mSv, 51% and 35% respectively, compared to those in 2007. The number of chest radiography was found to be 27.59% of them, the highest frequency of normal radiography. In this study, we developed a shielding device to minimize radiation exposure by shielding areas of the body which are unnecessary for image interpretation, during the chest radiography. And in order to verify its usefulness, we also measured the difference in entrance surface dose (ESD) and the absorbed dose, before and after using the device, by using an international standard pediatric (10 years) phantom and a glass dosimeter. In addition, we calculated the effective dose by using a Monte Carlo simulation-based program (PCXMC 2.0.1) and evaluated the reduction ratio indirectly by comparing lifetime attributable risk of cancer incidence (LAR). When using the protective device, the ESD decreased by 86.36% on average, nasal cavity $0.55{\mu}Sv$ (74.06%), thyroid $1.43{\mu}Sv$ (95.15%), oesophagus $6.35{\mu}Sv$ (78.42%) respectively, and the depth dose decreased by 72.30% on average, the cervical spine(upper spine) $1.23{\mu}Sv$ (89.73%), salivary gland $0.5{\mu}Sv$ (92.31%), oesophagus $3.85{\mu}Sv$ (59.39%), thyroid $2.02{\mu}Sv$ (73.53%), thoracic vertebrae(middle spine) $5.68{\mu}Sv$ (54.01%) respectively, so that we could verify the usefulness of the shielding mechanism. In addition, the effective dose decreased by 11.76% from $8.33{\mu}Sv$ to $7.35{\mu}Sv$ before and after wearing the device, and in LAR assessment, we found that thyroid cancer decreased to male 0.14 people (95.12%) and female 0.77 people (95.16%) per one million 10-year old children, and general cancers decreased to male 0.14 people (11.70%) and female 0.25 people (11.70%). Although diagnostic radiation examinations are necessary for healthcare such as the treatment of diseases, based on the ALARA concept, we should strive to optimize medical radiation by using this shielding device actively in the areas of the body unnecessary for the diagnosis.

• 대한방사선방어학회:학술대회논문집
• /
• 2011.11a
• /
• pp.98-99
• /
• 2011

• Journal of radiological science and technology
• /
• v.37 no.1
• /
• pp.7-14
• /
• 2014

By using a Chest Phantom(DUKE Phantom) focusing on dose reduction of diagnostic radiation field with the most use of artificial radiation, and attempt to reduce radiation dose studies technical radiation. Publisher of the main user of the X-ray Radiological technologists, Examine the effect of reducing the radiation dose to apply additional filtering of the X-ray generator. In order to understand the organ dose and effective dose by using the PC-Based Monte Carlo Program(PCXMC) Program, the patient receives, was carried out this research. In this experiment, by applying a complex filter using a copper and Al(aluminum,13) and filtered single of using only aluminum with the condition set, and measures the number of the disk of copper indicated by DUKE Phantom. The combination of the composite filtration and filtration of a single number of the disk of the copper is the same, with the PCXMC 2.0. Program looking combination of additional filtration fewest absorbed dose was calculated effective dose and organ dose. Although depends on the use mAs, The 80 kVp AP projection conditions, it is possible to reduce the effective amount of about 84 % from about 30 % to a maximum at least. The 120 kVp PA projection conditions, it is possible to reduce the effective amount of about 71 % from about 41 % to a maximum of at least. The organ dose, dose reduction rate was different in each organ, but it showed a decrease of dose rate of 30 % to up 100 % at least. Additional filtration was used on the imaging conditions throughout the study. There was no change in terms of video quality at low doses. It was found that using the DUKE Phantom and PCXMC 2.0 Program were suitable to calculate the effect of reducing the effective dose and organ dose.

• Radiation Oncology Journal
• /
• v.13 no.3
• /
• pp.277-283
• /
• 1995

Purpose : This study was performed to measure dose alteration at the air-tissue interface resulting from rebuild-up to the loss of charged particle equilibrium in the tissues around the air-tissue interfaces. Materials and Methods : The 6 and 10-MV photon beam in dual energy linear accelerator were used to measure the surface dose at the air-tissue interface The polystyrene phantom sized $25{\times}25{\times}5\;cm^3$ and a water phantom sized $29{\times}29{\times}48\;cm^3$ which incorporates a parallel-plate ionization chamber in the distal side of air gap were used in this study. The treatment field sizes were $5{\times}5\;cm^2,\;10{\times}10\;cm^2\;and\;20{\times}20\;cm^2$. Air cavity thickness was variable from 10 mm to 50 mm. The observed-expected ratio (OER) was defined as the ratio of dose measured at the distal junction that is air-tissue interface to the dose measured at the same point in a homogeneous phantom. Results : In this experiment, the result of OER was close or slightly over than 1.0 for the large field size but much less (about 0.565) than 1.0 for the small field size in both photon energy. The factors to affect the dose distribution at the air-tissue interface were the field size, the thickness of air cavity. and the photon energy. Conclusion : Thus, the radiation oncologist should take into account dose reduction at the air-tissue interface when planning the head and neck cancer especially pharynx and laryngeal lesions, because the dose can be less nearly $29{\%}$ than predicted value.

• Journal of Radiation Protection and Research
• /
• v.3 no.1
• /
• pp.23-28
• /
• 1978

In order to investigate corelation between contents of dioctylphthalate in polyvinylchloride blent dibutyl tin dilaulate with dibutyl tin maleate as stabilizer and the behaviors of radiation resistance as well as electrical conductivity on irradiated specimens, several observations were carried out. A characteristic peak observed in the range of $1,540-1,640cm^{-1}$ on infrared spectra shows such a sensitive response to radiation as the intensity decreases with increasing doses and that this tendency strongly depressed in the presence of plasticizer. It is seemingly attributed for origin of the peak to the existence of RCOO- ion resulting from dissociation of stabilizere, further the depressive effect of decreasing peak intensity influenced by radiation seems to be caused by resonance absorption in benzen ring being a consistituent of plasticizer. It is also suggestive to be use the peak behavior influenced by radiation as a criterion for the evaluation of radiation resistance of PVC. Further the results obtained from electrical conductivity measurement also exhibit reasonable characteristics explainable with views used for the interpretation of the peak behavior mentioned previousely.

• Journal of radiological science and technology
• /
• v.31 no.4
• /
• pp.401-406
• /
• 2008

The aim of this study is to evaluate contra-lateral breast (CLB) surface dose in Field-in-Field (FIF) technique for breast conserving surgery patients. For evaluation of surface dose in FIF technique, we have compared with other techniques, which were open fields (Open), metal wedge (MW), and enhanced dynamic wedge (EDW) techniques under same geometrical condition and prescribed dose. The three dimensional treatment planning system was used for dose optimization. For the verification of dose calculation, measurements using MOSFET detectors with Anderson Rando phantom were performed. The measured points for four different techniques were at the depth of 0cm (epidermis) and 0.5cm bolus (dermis), and spacing toward 2cm, 4cm, 6cm, 8cm, 10cm apart from the edge of tangential medial beam. The dose calculations were done in 0.25cm grid resolution by modified Batho method for inhomogeneity correction. In the planning results, the surface doses were differentiated in the range of $19.6{\sim}36.9%$, $33.2{\sim}138.2%$ for MW, $1.0{\sim}7.9%$, $1.6{\sim}37.4%$ for EDW, and for FIF at the depth of epidermis and dermis as compared to Open respectively. In the measurements, the surface doses were differentiated in the range of $11.1{\sim}71%$, $22.9{\sim}161%$ for MW, $4.1{\sim}15.5%$, $8.2{\sim}37.9%$ for EDW, and 4.9% for FIF at the depth of epidermis and dermis as compared to Open respectively. The surface doses were considered as underestimating in the planning calculation as compared to the measurement with MOSFET detectors. Was concluded as the lowest one among the techniques, even if it was compared with Open method. Our conclusion could be stated that the FIF technique could make the optimum dose distribution in Breast target, while effectively reduce the probability of secondary carcinogenesis due to undesirable scattered radiation to contra-lateral breast.

• Journal of radiological science and technology
• /
• v.35 no.4
• /
• pp.327-333
• /
• 2012

Purpose: To analyze the correlation between dose volume histograms(DVH) based on organ outer wall contour and organ wall delineation for bladder and rectum, and to compare the doses to these organs with the absorbed doses at the bladder and rectum. Material and methods: Individual CT based brachytherapy treatment planning was performed in 13 patients with cervical cancer as part of a prospective comparative trial. The external contours and the organ walls were delineated for the bladder and rectum in order to compute the corresponding dose volume histograms. The minimum dose in 0.1 $cm^3$, 1 $cm^3$, 2 $cm^3$, 5 $cm^3$, 10 $cm^3$ volumes receiving the highest dose were compared with the absorbed dose at the rectum and bladder reference point. Results: The bladder and rectal doses derived from organ outer wall contour and computed for volumes of 2 $cm^3$, provided a good estimate for the doses computed for the organ wall contour only. This correspondence was no longer true when large volumes were considered. Conclusion: For clinical applications, when volumes smaller than 5 $cm^2$ are considered, the dose-volume histograms computed from external organ contours for the bladder and rectum can be used instead of dose -volume histograms computed for the organ walls only. External organ contours are indeed easier to obtain. The dose at the ICRU rectum reference point provides a good estimate of the rectal dose computed for volumes smaller than 2 $cm^2$ only for a midline position of the rectum. The ICRU bladder reference point provides a good estimate of the dose computed for the bladder wall only in cases of appropriate balloon position.

• Progress in Medical Physics
• /
• v.25 no.3
• /
• pp.123-127
• /
• 2014

The Cs-137 irradiator is widely used to irradiate biological samples for radiobiological research. To obtain the accurate outcomes, correct measurements of the delivered absorbed dose to a sample is important. The IAEA protocols such as TRS-277 and TRS-398 were recommended for the Cs-137 reference dosimetry. However in TRS-398 protocol, currently known as the most practical dosimetry protocol, the quality factor ($k_{Q,Q_0}$) for Cs-137 gamma rays is not suggested. Therefore, the use of TRS-398 protocol is currently unavailable for the Cs-137 dosimetry directly. The calculation method previously introduced for high energy photon beams in radiotherapy was used for deriving the Cs-137 beam qualities ($k_{Q,Q_0}$) for the 15 commercially available farmer type ionization chambers in this study. In conclusion, $k_{Q,Q_0}$ values were ranged from 0.998 to 1.002 for Cs-137 gamma rays. These results can be used as the reference and dosimeter calibrations for Cs-137 gamma rays in the future radiobiological researches.