• Progress in Medical Physics
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• v.20 no.4
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• pp.253-259
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• 2009

We have developed standards based on international criterions for the quality control of dose tested by the measurement institutions of individual exposure doses through improving the reliability of data on the exposure dose of individuals working in radioactive environment and securing the accuracy and reliability of individual dose measurements. Laws related to radiation dose applied to domestic institutions refer to ANSI N13.11.1993, but currently, in U.S. and some other countries the measurement of radiation doses is based on ANSI N13.11.2001 that reduced test categories and tightened the standards. We made efforts to simplify the standards and to reduce the number of dosimeters required in experiment, and avoided preventing or hindering the use of future technologies not approved under the current law such as glass dosimeter and optical stimulation dosimeter. The Quality Management Manual of Radiation Dosimetry Service, Assessment Manual of Radiation Dosimetry Service Accreditation Program, and the Personnel Dosimetry Performance. Criteria for Testing are documents applicable in supervising laboratories.

• Journal of Radiation Protection and Research
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• v.27 no.3
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• pp.147-154
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• 2002

Purpose : Measurement of transmission dose is useful for in vivo dosimetry of QA purpose. The objective of this study is to develope an algorithm for estimation of tumor dose using measured transmission dose for open radiation field. Materials and Methods : Transmission dose was measured with various field size (FS), phantom thickness (Tp), and phantom chamber distance (PCD) with a acrylic phantom for 6 MV and 10 MV X-ray. Source to chamber distance (SCD) was set to 150 cm. Measurement was conducted with a 0.6 co Farmer type ion chamber. Using measured data and regression analysis, an algorithm was developed lot estimation of expected reading of transmission dose. Accuracy of the algorithm was tested with flat solid phantom with various settings. Results : The algorithm consisted of quadratic function of log(A/P) (where A/P is area-perimeter ratio) and tertiary function of PCD. The algorithm could estimate dose with very high accuracy for open square field, with errors within ${\pm}0.5%$. For elongated radiation field, the errors were limited to ${\pm}1.0%$. Conclusion : The developed algorithm can accurately estimate the transmission dose in open radiation fields with various treatment settings.

• Progress in Medical Physics
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• v.11 no.2
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• pp.109-116
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• 2000

One consideration of radiation delivery in cervical cancer is the complication of critical organs, e.g., bladder and rectum. The absorbed dose of bladder and rectum in HDR intracavitary brachytherapy is measured indirectly with TLD dosimetry A method for the complication reduction of bladder and rectum is suggested. For two-hundred cervical cancer patients, follow-up MRI images were reviewed and distances from cervical central axis to bladder and rectum and vaginal wall thickness were measured. The sealed TLDs were placed upon the gauze packing of the ovoids and the distances to the TLDs from the ovoid center were measured in the simulation film and actual doses of bladder and rectum were calculated. From published data, maximal tolerance doses of bladder and rectum were derived and based on the permissible doses per fraction in HDR brachytherapy the packing thicknesses were determined in both directions. The required minimal packing thicknesses for bladder and rectum were 0.43 and 0.92 cm, respectively. The results were compared with computer calculation using the Meisberger polynomial approach. It is our hope this study can be used for a guideline for users in clinic in estimating critical organ dose in bladder and rectum in HDR brachytherapy in vivo dosimetry.

• The Journal of the Korea Contents Association
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• v.11 no.9
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• pp.437-442
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• 2011

The purpose of this study is an measurement of the skin dose of a patient by using the OSLD(optically stimulated luminescent dosimeter) under several irradiation conditions of the X-ray beam for diagnostic radiography. The measurements of skin dose were performed for head, chest, and pelvis. And test of reproducibility was carried out at the chest. As a result, we obtained the skin dose at forehead of head to be 1.30 mSv. The skin doses at xiphoid process, breast and apex of the lung of the chest were acquired 0.92, 0.52 and 0.70 mSv, respectively. And we obtained the skin doses at the left pelvis and the right pelvis to be 2.78 and 3.08 mSv, respectively. As for reproducibility, a coefficient of variation was 0.033. The skin doses were exhibited the values corresponding from 1/100 to 1/17 of the dose limit of the public(50 mSv) at the deterministic effect. In order to make accurate measurements of the skin doses for each tube voltage, the measured values have to multiply by the displayed values of reader by a correction factor. The energy response of the OSLD with the tube voltage will be studied in the near future.

• Progress in Medical Physics
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• v.10 no.3
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• pp.151-157
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• 1999

The GafChromic film was used for the dosimetry of a balloon angio catheter filled with the radioisotope HO-166 for endovascular irradiation. The balloon angio catheter was 2 cm long and 3 mm in diameter when inflated. The isotope, Ho-166, was produced by the neutron bombardment using the research reactor in Korea Atomic Energy Research Insititute. Co-60 teletherapy beam was used for making H-D curve for the Gaf-Chromic film. The film dosimetry was measured with a videodensitometer. The radial dose distribution indicated that the absorbed dose dropped to about 20% of the surface dose at the 1 mm away from the balloon surface and at 5 mm position the dose decreased to below 1% of the surface dose. The result also shows that with the specific activity of Ho-l66, 250 mCi/ml it takes 230 seconds to deliver 1200 cGy to the region where is 1mm away from the balloon surface. The concentric isodose curves were also presented. The Ho-166 is an another alternative for endovascualr irradiation to prevent restenosis after PTCA (Percutaneous Trans Coronary Angioplasty)

• Journal of the Korean Society of Radiology
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• v.15 no.1
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• pp.85-91
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• 2021

The purpose of this study is to derive an equation to verify the accuracy of the dose rate for each component calculated at the measurement point outside the maze door when designing the maze door of 6 MV X-ray beam. Based on the component-specific dose rate calculation formula for the measurement point outside the maze door described in NCRP Report 151 and IAEA Safety Report Series 47, the dose rate calculation formula for each component when applying the values of the drawing-based parameters and the dose rate calculation formula for each component when applying the values of conservative parameters are derived. From the two dose rate calculation formulas for each component, the dose rate verification formula for each component at the measurement point outside the maze door was derived. The resulting dose rate verification formula for each component at the measurement point outside the maze door can be compared and analyzed whether the dose rate for each component at the measurement point outside the maze door calculated by the designer falls within the range of the dose rate obtained from the derived dose rate verification formula for each component. This verification formula is considered to be practically useful in verifying the accuracy of the dose rate for each component calculated by the designer.

• Radiation Oncology Journal
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• v.20 no.2
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• pp.172-178
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• 2002

Purpose : X-ray film over responds to low-energy photons in relative photon beam dosimetry because its sensor is based on silver bromide crystals, which are high-Z molecules. This over-response becomes a significant problem in clinical photon beam dosimetry particularly in regions outside the penumbra. In intensity modulated radiation therapy (IMRT), the radiation field is characterized by multiple small fields and their outside-penumbra regions. Therefore, in order to use film dosimetry for IMRT, the nature the source of the over-response in its radiation field need to be known. This study is aimed to verify and possibly improve film dosimetry for IMRT. Materials and Method : Modulated beams were constructed by a combination of five or seven different static radiation fields using 6 MeV X-rays. In order to verify film dosimetry, we used X-ray film and an ion chamber were used to measure the dose profiles at various depths in a phantom. In addition, in order to reduce the over-response, 0.01 inch thick lead filters were placed on both sides of the film. Results : The measured dose profiles showed a film over-response at the outside-penumbra and low dose regions. The error increased with depths and approached 15% at a maximum for the field size of $15{\times}15cm^2$ at 10 cm depth. The use of filters reduced the error to 3%, but caused an under-response of the dose in a perpendicular set-up. Conclusion : This study demonstrated that film dosimetry for IMRT involves sources of error due to its over-response to low-energy Photons. The use of filers can enhance the accuracy in film dosimetry for IMRT. In this regard, the use of optimal filter conditions is recommended.

• Journal of Radiation Protection and Research
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• v.15 no.2
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• pp.87-100
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• 1990

For the quantitative evaluation and assessment of radiation exposure from terrestrial component of natural environmental radiation, successive thermoluminescence dosimetry and periodical in-situ gamma ray spectrometry were carried out for a period of 24 months. LiF PTFE dise TLDs and $3&{\phi}{\times}3'$cylindrical NaI(Tl)scintill ation detector in association of portable multichannel analyzer (4096 ch) were used in this study. The doses measured were evaluated and assessed in terms of effective dose equivalent. As a concomitant output, the dose equivalent due to ionizing component of cosmic ray was able to be evaluated. According to the results obtained in terms of variance weighted mean, the annual effective dose equivalents of terrestrial gamma ray and cosmic ray ionizing component in Taejeon area came out to be $564{\pm}4\;{\mu}Sv(64.8{\pm}0.5nSv{\cdot}h^{-1}$ and $300{\pm}2\;{\mu}Sv(34.3{\pm}0.2nSv{\cdot}h^{-1}$, respectively, which are reasonable comparably with that appeared in UNSCEAR Report[28]as per caput annual effective dose equivalent in 'areas of normal background radiation'.

• Journal of Radiation Protection and Research
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• v.27 no.1
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• pp.37-49
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• 2002

The accuracy of radiation dose delivery to target volume is one of the most important factors for good local control and less treatment complication. In vivo dosimetry is an essential QA procedure to confirm the radiation dose delivered to the patients. Transmission dose measurement is a useful method of in vivo dosimetry and it's advantages are non-invasiveness, simplicity and no additional efforts needed for dosimetry. In our department, in vivo dosimetry system using measurement of transmission dose was manufactured and algorithms for estimation of transmission dose were developed and tested with phantom in various conditions successfully. This system was applied in clinic to test stability, reproducibility and applicability to daily treatment and the accuracy of the algorithm. Transmission dose measurement was performed over three weeks. To test the reproducibility of this system, X-tay output was measured before daily treatment and then every hour during treatment time in reference condition(field size; $10 cm{\times} 10 cm$, 100 MU). Data of 11 patients whose pelvis were treated more than three times were analyzed. The reproducibility of the dosimetry system was acceptable with variations of measurement during each day and over 3 week period within ${\pm}2.0%$. On anterior- posterior and posterior fields, mean errors were between -5.20% and +2.20% without bone correction and between -0.62% and +3.32% with bone correction. On right and left lateral fields, mean errors were between -10.80% and +3.46% without bone correction and between -0.55% and +3.50% with bone correction. As the results, we could confirm the reproducibility and stability of our dosimetry system and its applicability in daily radiation treatment. We could also find that inhomogeneity correction for bone is essential and the estimated transmission doses are relatively accurate.

• Radioisotope journal
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• v.13 no.4
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• pp.56-61
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• 1998