• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.337-343
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• 2014

Purpose : The aim of this study is to evaluate unwanted scattered dose to ovary by scattering and leakage generated from treatment fields of Tomotherapy for childbearing woman with breast cancer. Materials and Methods : The radiation treatments plans for left breast cancer were established using Tomotherapy planning system (Tomotherapy, Inc, USA). They were generated by using helical and direct Tomotherapy methods for comparison. The CT images for the planning were scanned with 2.5 mm slice thickness using anthropomorphic phantom (Alderson-Rando phantom, The Phantom Laboratory, USA). The measurement points for the ovary dose were determined at the points laterally 30 cm apart from mid-point of treatment field of the pelvis. The measurements were repeated five times and averaged using glass dosimeters (1.5 mm diameter and 12 mm of length) equipped with low-energy correction filter. The measures dose values were also converted to Organ Equivalent Dose (OED) by the linear exponential dose-response model. Results : Scattered doses of ovary which were measured based on two methods of Tomo helical and Tomo direct showed average of $64.94{\pm}0.84mGy$ and $37.64{\pm}1.20mGy$ in left ovary part and average of $64.38{\pm}1.85mGy$ and $32.96{\pm}1.11mGy$ in right ovary part. This showed when executing Tomotherapy, measured scattered dose of Tomo Helical method which has relatively greater monitor units (MUs) and longer irradiation time are approximately 1.8 times higher than Tomo direct method. Conclusion : Scattered dose of left and right ovary of childbearing women is lower than ICRP recommended does which is not seriously worried level against the infertility and secondary cancer occurrence. However, as breast cancer occurrence ages become younger in the future and radiation therapy using high-precision image guidance equipment like Tomotherapy is developed, clinical follow-up studies about the ovary dose of childbearing women patients would be more required.

• Journal of Radiation Protection and Research
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• v.35 no.3
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• pp.111-116
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• 2010

Ionizing radiation is most widely used for X-Ray examination among all artificial radiation exposure, it takes up the largest proportion. Even in Korea, the medical exposure by diagnostic X-Ray examination takes up 17.4% of all radiation exposure. It takes up 92% even in artificial radiation exposure. There were 111,567 cases X-Ray radiography for skull diagnosis in 2007, which is 3% annual increase since 2004. Thus, It is need to establish the diagnostic reference level and the medical facilities as a diagnostic reference level to optimize radiation protection of the patients and to reduce the doses of X-ray. In this paper, we survey patient dose on skull radiography - collected from 114 medical facilities nationwide by using human phantom and glass dosimeter. When the patient dose for the skull radiography was measured and evaluated to establish the diagnostic reference level, 2.23 mGy was established for posterior-anterior imaging and 1.87 mGy for lateral imaging was established. The posterior-anterior skull radiography entrance surface dose of 2.23 is less than the guidance level of 5 mGy from the global organizations such as World Health Organization (WHO) and International Atomic Energy Agency (IAEA), and 1.87 mGy for the lateral skull imaging is less than the guidance level of 3 mGy, which is guided by the global organizations such as World Health Organization (WHO) and International Atomic Energy Agency (IAEA).

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

• Progress in Medical Physics
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• v.24 no.4
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• pp.295-302
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• 2013

We estimated secondary scattered and leakage doses for intensity-modulated radiotherapy (IMRT), volumetric arc therapy (VMAT) and tomotherapy (TOMO) in patients with liver cancer. Five liver patients were planned by IMRT, VMAT and TOMO. Secondary scatter (and leakage) dose and organ equivalent doses (OEDs) are measured and estimated at various points 20 to 80 cm from the iso-center by using radiophotoluminescence glass dosimeter (RPLGD). The secondary dose per Gy from IMRT, VMAT and TOMO for liver cancer, measured 20 to 80 cm from the iso-center, are 0.01~3.13, 0.03~2.34 and 0.04~1.29 cGy, respectively. The mean values of relative OED of secondary dose of VMAT and TOMO for five patients, which is normalized by IMRT, measured as 75.24% and 50.92% for thyroid, 75.14% and 40.61% for bowel, 72.30% and 47.77% for rectum, 76.21% and 49.93% for prostate. The secondary dose and OED from TOMO is relatively low to those from IMRT and VMAT. OED based estimation suggests that the secondary cancer risk from TOMO is less than or comparable to the risks from conventional IMRT and VMAT.

• Journal of Biomedical Engineering Research
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• v.38 no.5
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• pp.256-263
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• 2017

By using the buildup characteristics of the radiophotoluminescence glass dosimeter(RPLGD), it is aimed to help the measurement of the accurate dose by measuring the radiation dose according to the time of the glass element. Five glass elements were arranged on the table and the source to image receptor distance(SID) was set to 100 cm for the build-up radiation dose measurement of the fluorescent glass dosimeter glass element(GD-352M). Radiation doses and saturation rates were measured over time according to irradiation time, with the tube voltage (30, 60, 90 kVp) and tube current (50, 100 mAs) Repeatability test was repeated ten times to measure the coefficient of variation. The radiation dose increased from 0.182 mGy to 12.902 mGy and the saturation rate increased from 58.3% with increasing exposure condition and time. The coefficient of variation of the glass elements of the fluorescent glass dosimeter was ranged from 0.2 to 0.77 according to the X - ray exposure conditions. X - ray exposure showed that the radiation dose and saturation rate were increased with buildup characteristics, and degeneration of glass elements was not observed. The reproducibility of the variation coefficient of the radiation generator was included within the error range and the reproducibility of the radiation dose was excellent.

• Journal of Radiation Industry
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• v.11 no.3
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• pp.131-137
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• 2017

To compare the radiation dose and image noise of low dose computed tomography (CT) and high resolution CT using the fixed tube current technique and automatic tube current modulation (CARE Dose 4D). Chest CT and human anthropomorphic phantom were used the RPL (radiophotoluminescence) dosimeters. For image evaluation, standard deviation of mean CT attenuation coefficient and CT attenuation coefficient was measured using ROI analysis function. The effective dose was calculated using CTDIvol and DLP. CARE Dose 4D was reduced by 74.7% and HRCT by 64.4% compared to the fixed tube current technique in low dose CT of chest phantom. In CTDIvol and DLP, the dose of CARE Dose 4D was reduced by fixed tube current technique. For effective dose, CARE Dose 4D was reduced by 47% and HRCT by 46.9% compared to the fixed tube current method, and the dose of CARE Dose 4D was significantly different (p<.05). Noise in the image was higher than that in the fixed tube current technique. Noise difference in the image of CARE Dose 4D in low dose CT was significant (p<.05). The low radiation dose and the noise difference of the CARE Dose 4D were compared with the fixed tube current technique in low dose CT and HRCT using chest phantom. The radiation doses using CARE Dose 4D were in accordance with the national and international dose standards. CARE Dose 4D should be applied to low dose CT and HRCT for clinical examination.

• Journal of radiological science and technology
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• v.32 no.3
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• pp.299-306
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• 2009

Purpose : To compare radiation dose for coronary CT angiography (CTA) obtained with 6 examination protocols such as a retrospectively ECG gated helical scan, a prospectively ECG gated sequential scan, low kVp technique, and cardiac dose modulation technique. Materials and Methods : Coronary CTA was performed by using 6 current clinical protocols to evaluate effective dose and organ dose in primary beam area with anthropomorphic female phantom and glass dosimetric system in 64 channel multi-detector CT. After acquiring topograms of frontal and lateral projection with 80 kVp and 10 mA, main coronary scan was done with 0.35 sec tube rotation time, 40 mm collimation ($0.625\;mm{\times}64\;ea$), small scan field of view (32 cm diameter), 105 mm scan length. Heart beat rate of phantom was maintained 60 bpm in ECG gating. In constant mAs technique 120 kVp, 600 mA was used, and 100 kVp for low kVp technique. In a retrospectively ECG gated helical CT technique 0.22 pitch was used, peak mA (600 mA) was adopted in range of $40{\sim}80%$ of R-R interval and 120mA(80% reduction) in others with cardiac dose modulation. And 210 mAs was used without cardiac dose modulation. In a prospectively ECG gated sequential CT technique data were acquired at 75% R-R interval (middle diastolic phase in cardiac cycle), and 120 msec additional padding of the tube-on time was used. For effective dose calculation region specific conversion factor of dose length product in thorax was used, which was recommended by EUR 16262. Results : The mean effective dose for conventional coronary CTA without cardiac dose modulation in a retrospectively ECG gated helical scan was 17.8 mSv, and mean organ dose of heart was 103.8 mGy. With low kVp and cardiac dose modulation the mean effective dose showed 54.5% reduction, and heart dose showed 52.3% reduction, compared with that of conventional coronary CTA. And at the sequential scan(SnapShot pulse mode) under prospective ECG gating the mean effective dose was 4.9 mSv, this represents an 72.5% reduction compared with that of conventional coronary CTA. And heart dose was 33.8 mGy, this represents 67.4% reduction. In the sequential scan technique under prospective ECG gating with low kVp the mean effective dose was 3.0 mSv, this represents an 83.2% reduction compared with that of conventional coronary CTA. And heart dose was 17.7 mGy, this represents an 82.9% reduction. Conclusion : In coronary CTA at retrospectively ECG gated helical scan, cardiac dose modulation technique using low kVp reduced dose to 50% above compared with the conventional helical scan. And the prospectively ECG gated sequential scan offers substantially reduced dose compared with the traditional retrospectively ECG gated helical scan.

• Journal of radiological science and technology
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• v.32 no.4
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• pp.401-410
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• 2009

Purpose : Pelvis and lumbar spine radiography, among various types of diagnostic radiography, include gonads of the human body and give patients high radiation dose. Nevertheless, diagnostic reference levels for patient radiation dose in pelvis and lumbar spine radiography has not yet been established in Korea. Therefore, the radiation dose that patients receive from pelvis and lumbar radiography is measured and the diagnostic reference level on patient radiation dose for the optimization of radiation protection of patients in pelvis and lumbar spine radiography was established. Methods : The conditions and diagnostic imaging information acquired during the time of the postero-anterior view of the pelvis and the postero-anterior and lateral view of the lumbar spine at 125 medical institutions throughout Korea are collected for analysis and the entrance surface dose received by patients is measured using a glass dosimeter. The diagnostic reference levels for patient radiation dose in pelvis and lumbar spine radiography to be recommended to the medical institutes is arranged by establishing the dose from the patient radiation dose that corresponds to the 3rd quartile values as the appropriate diagnostic reference level for patient radiation dose. Results : According to the results of the assessment of diagnostic imaging information acquired from pelvis and lumbar spine radiography and the measurement of patient entrance surface dose taken at the 125 medical institutes throughout Korea, the tube voltage ranged between 60~97 kVp, with the average use being 75 kVp, and the tube current ranged between 8~123 mAs, with the average use being 30 mAs. In the posteroanterior and lateral views of lumbar spine radiography, the tube voltage of each view ranged between 65~100 kVp (average use: 78 kVp) and 70~109 kVp (average use: 87 kVp), respectively, and the tube current of each view ranged between 10~100 mAs(average use: 35 mAs) and between 8.9~300 mAs(average use: 64 mAs), respectively. The measurements of entrance surface dose that patients receive during the pelvis and lumbar spine radiography show the following results: in the posteroanterior view of pelvis radiography, the minimum value is 0.59 mGy, the maximum value is 12.69 mGy and the average value is 2.88 mGy with the 1st quartile value being 1.91 mGy, the median being 0.59 mGy, and the 3rd quartile value being 3.43 mGy. Also, in the posteroanterior view of lumbar spine radiography, the minimum value is 0.64 mGy, the maximum value is 23.84 mGy, and the average value is 3.68 mGy with the 1st quartile value being 2.41 mGy, the median being 3.40 mGy, and the 3rd quartile value being 4.08 mGy. In the lateral view of lumbar spine radiography, the minimum value is 1.90 mGy, the maximum value is 45.42 mGy, and the average value is 10.08 mGy with the 1st quartile value being 6.03 mGy, the median being 9.09 mGy and the 3rd quartile value being 12.65 mGy. Conclusions : The diagnostic reference levels for patient radiation dose to be recommended to the medical institutes in Korea is 3.42 mGy for the posteroanterior view of pelvis radiography, 4.08 mGy for the posteroanterior view of lumbar spine radiography, and 12.65 mGy for the lateral view of lumbar spine radiography. Such values are all lower than the values recommended by 6 international organizations including World Health Organization, where the recommended values are 10 mGy for the posteroanterior view of pelvis radiography, 10 mGy for the posteroanterior view of lumbar spine radiography and 30 mGy for the lateral view of lumbar spine radiography.

• The Journal of Korean Society for Radiation Therapy
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• v.32
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• pp.7-15
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• 2020

Purpose: In modern radiotherapy technology, several methods of image guided radiation therapy (IGRT) are used to deliver accurate doses to tumor target locations and normal organs, including CBCT (Cone Beam Computed Tomography) and other devices, ExacTrac System, other than CBCT equipped with linear accelerators. In previous studies comparing the two systems, positional errors were analysed rearwards using Offline-view or evaluated only with a Yaw rotation with the X, Y, and Z axes. In this study, when using CBCT and ExacTrac to perform 6 Degree of the Freedom(DoF) Online IGRT in a treatment center with two equipment, the difference between the set-up calibration values seen in each system, the time taken for patient set-up, and the radiation usefulness of the imaging device is evaluated. Materials and Methods: In order to evaluate the difference between mobile calibrations and exposure radiation dose, the glass dosimetry and Rando Phantom were used for 11 cancer patients with head circumference from March to October 2017 in order to assess the difference between mobile calibrations and the time taken from Set-up to shortly before IGRT. CBCT and ExacTrac System were used for IGRT of all patients. An average of 10 CBCT and ExacTrac images were obtained per patient during the total treatment period, and the difference in 6D Online Automation values between the two systems was calculated within the ROI setting. In this case, the area of interest designation in the image obtained from CBCT was fixed to the same anatomical structure as the image obtained through ExacTrac. The difference in positional values for the six axes (SI, AP, LR; Rotation group: Pitch, Roll, Rtn) between the two systems, the total time taken from patient set-up to just before IGRT, and exposure dose were measured and compared respectively with the RandoPhantom. Results: the set-up error in the phantom and patient was less than 1mm in the translation group and less than 1.5° in the rotation group, and the RMS values of all axes except the Rtn value were less than 1mm and 1°. The time taken to correct the set-up error in each system was an average of 256±47.6sec for IGRT using CBCT and 84±3.5sec for ExacTrac, respectively. Radiation exposure dose by IGRT per treatment was measured at 37 times higher than ExacTrac in CBCT and ExacTrac at 2.468mGy and 0.066mGy at Oral Mucosa among the 7 measurement locations in the head and neck area. Conclusion: Through 6D online automatic positioning between the CBCT and ExacTrac systems, the set-up error was found to be less than 1mm, 1.02°, including the patient's movement (random error), as well as the systematic error of the two systems. This error range is considered to be reasonable when considering that the PTV Margin is 3mm during the head and neck IMRT treatment in the present study. However, considering the changes in target and risk organs due to changes in patient weight during the treatment period, it is considered to be appropriately used in combination with CBCT.

• Journal of Korean Elementary Science Education
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• v.24 no.3
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• pp.259-267
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• 2005

This study was to investigate the elementary students' preconception on the brightness of electric bulb and degree of consistency on their preconceptions. Participants were 160 students of fifth graders in Seoul area. They had already teamed about the brightness of series circuit and parallel circuit of batteries. After they solved six problems in the same context, we provided them a pair of circuit which was an anomalous situation. And then they conducted CCLT (Cognitive Conflict Level Test). Elementary school students showed various preconceptions when they explained the light of bulb of two Simple electric Circuits. Many Students Consistently Showed the Scientific misconceptions like 'the light of bulb of two simple electric circuits was that the more batteries and the fewer bulbs were brighter.' The level of consistency that students presented scientific misconceptions was grouped all of four, such as 'high, middle, low, and nothing.' Therefore the higher scientific achievement they have, the higher consistency they have. As the students had high consistency level, they revealed high cognitive conflict level significantly. This high consistency will help them to change their preconception on the brightness of electric bulb and their cognitive conflict.