• Journal of Radiation Protection and Research
• /
• v.26 no.3
• /
• pp.183-190
• /
• 2001

The activity concentration of primordial radionuclides i.e., $^{238}U$ series, $^{232}Th$ series and $^{40}K$, in soil samples collected from Udagamandalam environment, have been measured by employing NaI (Tl) Gamma ray Spectrometer. The absorbed gamma dose rate has also been simultaneously measured by using both Environmental Radiation Dosimeter at each soil sampling location (ambient gamma dose) as well as from the gamma dose derived from the activity concentration of the primordial radionuclides. The results of activity concentration of each radio nuclides in soil, absorbed dose rate in air due to soil activity and possible cosmic radiation at each location along with human effective dose equivalent for Udagamandalam environment are presented and discussed.

• Journal of the Korean Society of Radiology
• /
• v.12 no.6
• /
• pp.763-768
• /
• 2018

Although the development of radiation therapy techniques has made the treatment more precise, exposure by radiation is unavoidable beyond the treatment site. In this study, we wanted to evaluate the absorbed dose according to the thickness of the bolus on the opposite side of the treatment in radiation treatment for breast cancer and to analyze the effect of dose reduction. An experiment was conducted on Rando phantom using VMAT treatment methods. Five points of A, B, C, D, and E were selected for the breast opposite the treatment, and when the dosimeters of 5, 10, 15, and 20 mm were used. The highest absorbed dose at point D closest to the treatment point was measured and lowest at point B furthest from the treatment point. The mean absorbed dose was 8.61 cGy When the bolus is not used and 8.10, 7.94, 8.06, and 8.10 cGy Depending on the thickness of the bolus. In this study, bolus was intended to be used to analyze the dose-reducing effects of breasts on the other side of the treatment. The results of the study showed the effect of dose reduction and the appropriate bolus thickness should be set up to reduce the dose in normal tissues.

• Journal of Radiation Protection and Research
• /
• v.16 no.2
• /
• pp.17-26
• /
• 1991

Beta ray $(^{90}Sr+^{90}Y)$ absorbed dose at tissue surface was measured from the distance of 30cm by use of extrapolation chamber. In the measurement, following factors were considered: effective area of collecting electrode, polarity effect, ion recombination and window attenuation. The measured absorbed dose rate at tissue surface was $1.493{\mu}Gy/sec$ with ${\pm}2.9%$.

• Imaging Science in Dentistry
• /
• v.37 no.3
• /
• pp.149-156
• /
• 2007

Purpose: The purpose of this study was to measure the absorbed dose and to calculate the effective dose for periapical radiography done by portable intraoral x-ray machines. Materials and Methods: 14 full mouth, upper posterior and lower posterior periapical radiographs were taken by wall-type 1 and portable type 3 intraoral x-ray machines. Thermoluminescent dosemeters were placed at 23 sites at the layers of the tissue-equivalent ART woman phantom for dosimetry. Average tissue absorbed dose and radiation weighted dose were calculated for each major anatomical site. Effective dose was calculated using 2005 ICRP tissue weighted factors. Results: On 14 full mouth periapical radiographs, the effective dose for wall-type x-ray machine was 30 Sv; for portable x-ray machines were 30 Sv, 22 Sv, 36 Sv. On upper posterior radiograph, the effective dose for wall-type x-ray machine was 4 Sv; for portable x-ray machines doses were 4 Sv, 3 Sv, 5 Sv. On lower posterior radiograph, the effective dose for wall type x-ray machine was 5 Sv; for portable x-ray machines doses were 4 Sv, 4 Sv, 5 Sv. Conclusion: Effective doses for periapical radiographs performed by portable intraoral x-ray machines were similar to doses for periapical radiographs taken by wall type intraoral x-ray machines.

• The Journal of the Korea Contents Association
• /
• v.18 no.1
• /
• pp.232-240
• /
• 2018

This study is to suggest a method to evaluate the detector performance using change of absorbed dose and histogram according to sensitivity change of Auto Exposure Control(AEC). The experiment site is skull, abdomen pelvis and the accuracy of the detector was evaluated by measuring the absorbed dose of the detector sensitivity S200, S400, S800, S1000. Also the dynamic range of the detector was evaluated through the histogram analysis. As a result, the absorbed dose decreased gradually as the sensitivity was set higher from S200 to S1000. And through the sensitivity histogram analysis, as the sensitivity of the skull is set higher, the amount of information at both ends of the histogram is lost. Abdomen and pelvis areas showed underflow phenomena in which the amount of information in the first part of the histogram was lost as the sensitivity was set higher. In conclusion, the detector accurately implemented the sensitivity change, but the dynamic range of the image due to the sensitivity change of the AEC due to the deterioration of the detector performance can not be realized properly and it was found that the evaluation through the absorbed dose and the histogram is useful when evaluating the performance of the detector.

• Journal of the Korean Society of Radiology
• /
• v.17 no.7
• /
• pp.1157-1164
• /
• 2023

This study measures the additional dose for each treatment area using kV X-ray based OBI (On-Board Imager) and CBCT (Cone-Beam CT), which have excellent spatial resolution and contrast, and evaluates the adequacy and stability of radiation management aspects of IGRT. The subjects of the experiment were examined with OBI and CBCT attached to a linear accelerator (Clinac IX), and ring-shaped Halcyon CBCT under imaging conditions for each treatment area, and the dose at the center was measured using an ion chamber. OBI single fraction dose was measured as 0.77 mGy in the head area, 3.04 mGy in the chest area, and 7.19 mGy in the pelvic area. The absorbed doses from the two devices, Clinac IX CBCT and Halcyon CBCT, were measured to be similar in the pelvic area, at 70.04 mGy and 70.45 mGy. and in chest CBCT, the Clinac IX absorbed dose (70.05 mGy) was higher than the Halcyon absorbed dose (21.01 mGy). The absorbed dose to the head area was also higher than that of Clinac IX (9.08 mGy) and Halcyon (5.44 mGy). In kV X-ray-based IGRT, additional radiation exposure due to photoelectric absorption may affect the overall volume of the treatment area, and caution is required.

• Journal of Radiation Protection and Research
• /
• v.13 no.2
• /
• pp.21-28
• /
• 1988

Absorbed dose in water was analyzed by Burlin's general cavity theory for medium X-ray energy region (HVL : 0.29, 0.84, 1.60, 2.62mm Cu) using LiF : PTFE TL dosimeter(0.4 mm ${\times}\;{\phi}$ 12.5mm, hot-pressed LiF TLD-700) which was enclosed in lucite capsule. The absorbed dose rate at 5cm depth in water phantom was determined with measurement error of ${\pm}5%$. This result was compared to that of the ionization method, indirectly absolute measurement method, of which measurement error of ${\pm}2%$. The difference between these two results lies within measurement error of LiF : PTFE method. Therefore, the absorbed dose in water obtained by LiF: PTFE is reliable, and this result suggests the base to estimate dose-equivalent for medium X-rays.

• The Journal of the Korea Contents Association
• /
• v.10 no.6
• /
• pp.336-343
• /
• 2010

Coronary artery CT angiography has short scanning length, the exposure dose is high. Therefore, it is required to study on the organ dose when using MDCT. We compared the differences between the absorbed dose and effective dose in the major organs assessing the absorbed dose in the major organs by 16-MDCT and 64-MDCT in the subjects with coronary artery CT angiography, the same protocol by 16-MDCT and 64-MDCT. As a result, the great orders of absorbed dose when conducting coronary artery CT angiography had been shown as heart, stomach, liver, pancreas, kidney, spleen, large intestine, lung, small intestine, thyroid gland, ovary, bladder, and orbit with the absorbed dose distribution of $0.538{\pm}0.026(Mean{\pm}SD,\;p<0.05)mGy{\sim}71.316{\pm}4.316mGy$ in 16-MDCT, and heart, stomach, pancreas, spleen, liver, kidney, small intestine, large intestine, lung, thyroid gland, ovary, bladder, and orbit with the absorbed dose distribution of $0.87{\pm}0.01mGy{\sim}115.26{\pm}1.59mGy$ in 64-MDCT, demonstrating some different distributions. The exposed doses to the patient per one time scanning with coronary artery CT angiography were $71.316{\pm}4.316mGy$ in 16-MDCT as the absorbed dose based on the heart and $115.26{\pm}1.59mGy$ in 64-MDCT. The effective doses were 7.41 mSv and 12.11 mSv in 16 and 64-MDCT, respectively. Taking into account the results of brain CT with 2.8 mSv that has comparatively large scanning length and size, facial CT 0.8 mSv, chest CT 5.7 mSv, pelvic CT 7.2 mSv, and abdominal and pelvic CT 14.4 mSv, it is very high considering the scanning length of 13 cm limited to the heart for the scanning range.

• Nuclear Engineering and Technology
• /
• v.52 no.10
• /
• pp.2410-2414
• /
• 2020

Heavy ions have a high potential for destroying deep tumors that carry the highest dose at the peak of Bragg. The peak caused by a single-energy carbon beam is too narrow, which requires special measures for improvement. Here, carbon-12 (¹²C) ion with different energies has been used as a source for calculating the dose distribution in the water phantom, soft tissue and bone by the code of Monte Carlobased FLUKA code. By increasing the energy of the initial beam, the amount of absorbed dose at Bragg peak in all three targets decreased, but the trend for this reduction was less severe in bone. While the maximum absorbed dose per bone-mass unit in energy of 200 MeV/u was about 30% less than the maximum absorbed dose per unit mass of water or soft tissue, it was merely 2.4% less than soft tissue in 400 MeV/u. The simulation result showed a good agreement with experimental data at GSI Darmstadt facility of biophysics group by 0.15 cm average accuracy in Bragg peak positioning. From 200 to 400 MeV/u incident energy, the Bragg peak location increased about 18 cm in soft tissue. Correspondingly, the bone and soft tissue revealed a reduction dose ratio by 2.9 and 1.9. Induced neutrons did not contribute more than 1.8% to the total energy deposited in the water phantom. Also during ¹²C ion bombardment, secondary fragments showed 76% and 24% of primary 200 and 400 MeV/u, respectively, were present at the Bragg-peak position. The combined treatment of carbon ions with neutron or electron beams may be more effective in local dose delivery and also treating malignant tumors.

• Journal of radiological science and technology
• /
• v.43 no.6
• /
• pp.443-451
• /
• 2020

This study is to evaluate absorbed dose from right lung for brachytherapy and to estimate the effects of tissue heterogeneities on dose distribution for Iridium-192 source using Monte Carlo simulation. The study employed Geant4 code as Monte Carlo simulation to calculate the dosimetry parameters. The dose distribution of Iridium-192 source in solid water equivalent phantom including aluminium plate or steel plate inserted was calculated and compared with the measured dose by the ion chamber at various distances. And the simulation was used to evaluate the dose of gamma radiation absorbed in the lung organ and other organs around it. The dose distribution embedded in right lung was calculated due to the presence of heart, thymus, spine, stomach as well as left lung. The geometry of the human body was made up of adult male MIRD type of the computational human phantom. The dosimetric characteristics obtained for aluminium plate inserted were in good agreement with experimental results within 4%. The simulation results of steel plate inserted agreed well with a maximum difference 2.75%. Target organ considered to receive a dose of 100%, the surrounding organs were left the left lung of 3.93%, heart of 10.04%, thymus of 11.19%, spine of 12.64% and stomach of 0.95%. When the statistical error is performed for the computational human phantom, the statistical error of value is under 1%.