• Radiation Oncology Journal
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• v.4 no.2
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• pp.89-97
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• 1986

Using as assay for jejunal crypt stem cell survival, dose-response curves for the reproductive capacity of crypt stem cells of mouse jejunum exposed to multifractionated gamma-ray irradiation (single, 2, 3, 4, 5, 8, 10, 12, and 16 fractions) were analyzed and single-dose survival curve of these cells was constructed. The following conclusion were drawn: 1) Survival curves for higher numbers of dose fractions were displaced to higher dose, and characterized by increasingly shallower slopes. 2) The single-dose survival curve had broad shoulder, Dq=460 cGy, remaining near-exponential over initial dose range 0 to 300 cGy, with initial slope 1Do=474 cGy. 3) At fractionated dose En the range of 180 to 450 cGy, the average recovered dose per fraction interval was approximately $50\%$ of the dose per fraction. 4) The value of $\alpha/\beta$ ratio by using of linear regression analysis for the reciprocal dose plots was 8.3 Gy which lied in the range of 6-14 Gy for early-reacting tissues. 5) The linear-quadratic model for dose-response formula offers valid approximations for at 1 doses to be used in radiotherapy, only two parameters to be determined, and considerable convenience in practical applications.

• Journal of Radiation Protection and Research
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• v.7 no.1
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• pp.34-48
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• 1982

The prime purpose of this study is to realize an index quantity, absorbed dose index, defined by the ICRU for the characterization of ambient radiation level at any location for the purpose of radiation protection. The experiment has been designed to be carried out in two phases, namely, preliminary and main experiment. In the primary study a 30cm diameter sphere of polyethylene was used, while in the main experiment that of tissue equivalent material was fabricated and used. Both experiments were performed in the gamma-ray fields of $^{137}Cs\;and\;^{60}Co$, and in a neutron beam of thermal column of the TRIGA MARK-II research reactor. In the measurement of gamma-ray absorbed dose TLD-700 $(^{7}LiF)$ chips were used, and for the neutron dose both Au activation foils and TLD chips (TLD-600 $(^{6}LiF)$ and TLD-700 for the discrimination of gamma-ray contribution) were used. Theoretical assessment of the absorbed dose in the sphere phantom has been carried out in accordance with the Ehrlich's idea that deduced on the basis of Burlin's cavity theory in the case of gamma-ray irradiation. For the analysis of neutron dose fluence-KERMA rate conversion method was used. The explanation on the dose assessment is given in detail. Results obtained were numerically and statistically analyzed and the depth dose distributions are presented in the graphic forms with normalized values. In the concluding remarks, the possibility and difficulty of realizing the index quantity, including questions and problems to be solved are mentioned.

• Journal of the Korean Society of Radiology
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• v.17 no.2
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• pp.243-248
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• 2023

This study aims to analyze the secondary carcinogenesis rate caused by exposure of organs at risk of damage using a glass dosimeter during radiosurgery in vestibular schwannoma disease. Using a pediatric phantom of human tissue equivalent material, the volume of the tumor was set to a total of three volumes: 0.506 cm³, 1.008 cm³, and 2.032 cm³, and a radiosurgery plan was established with an average dose of 18.4 ± 3.4 Gy. After mounting the human body phantom on the table of surgical equipment, glass dosimeters were placed on the right eye, left eye, thyroid gland, thymus, right lung, and left lung to measure the exposure dose, respectively. In this study, the incidence of secondary cancer due to exposure to damaged organs during gamma knife radiosurgery in vestibular schwannoma disease with the largest tumor volume of 2.032 cm³ was measured with a glass dosimeter. This study studies the risk of secondary radiation exposure dose that can occur during stereotactic radiosurgery, and it is considered that it will be used as basic data in the field of radiation damage related to the stochastic effect of radiation in the future.

• Journal of radiological science and technology
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• v.40 no.3
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• pp.461-468
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• 2017

This study measured and compared the protective clothing using Pb used for shielding in a diagnostic X-ray energy range, and the shielding rates of X-ray fusion shielding materials using Si and $TiO_2$. For the experiment, a pad type shielding with a thickness of 1 mm was prepared by mixing $Si-TiO_2$, and the X-ray shielding rate was compared with 0.5 mmPb plate of The shielding rate of shielding of 0.5 mmPb plate 95.92%, 85.26 % based on the case of no shielding under each 60 kVp, 100 kVp tube voltage condition. When the shielding of $Si-TiO_2$ pad was applied, the shielding rate equal to or greater than 0.5 mmPb plate was obtained at a thickness of 11 mm or more, and the shielding rate of 100% or more was confirmed at a thickness of 13 mm in 60 kVp condition. When the shielding of $Si-TiO_2$ pad was applied, the shielding rate equal to or greater than 0.5 mmPb plate was obtained at a thickness of 17 mm or more, and a shielding rate of 0.5 mmPb plate was observed at a thickness of 23 mm in 100 kVp condition. Through the results of this study, We could confirm the possibility of manufacturing radiation protective materials that does not contain lead hazard using various metalic compound and liquid Si. This study shows that possibility of liquid Si and other metalic compound can harmonize easily. Beside, It is flexible and strong to physical stress than Pb obtained radiation protective closthes. But additional studies are needed to increase the shielding rate and reduce the weight.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.225-232
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• 2014

Purpose : The purpose of this study was to evaluate the surface and superficial dose for patients requiring postmastectomy radiation therapy(PMRT) with different treatment techniques. Materials and Methods : Computed tomography images were acquired for the phantom(I'mRT, IBA) consisting of tissue equivalent material. Hypothetical chestwall and lung were outlined and modified. Five treatment techniques(Wedged Tangential; WT, 4-field IMRT, 7-field IMRT, TOMO DIRECT, TOMO HELICAL) were evaluated using only 6MV photon beam. GafChromic EBT3 film was used for dose measurements at the surface and superficial dose. Surface dose profiles around the phantom were obtained for each treatment technique. For superficial dose measurements, film were used inside the phantom and analyzed superficial region for depth from 1-6mm. Results : TOMO DIRECT showed the highest surface dose by 47~70% of prescribed dose, while 7-field IMRT showed the lowest by 35~46% of prescribed dose. For the WT, 4-field IMRT and 7-field IMRT, superficial dose were measured over 60%, 70%, and 80% for 1mm, 2mm, and 5mm depth, respectively. In case of TOMO DIRECT and TOMO HELICAL, over 75%, 80%, and 90% of prescribed dose was measured, respectively. Surface and superficial dose range were uniform in overall chestwall for the 7-field IMRT and TOMO HELICAL. In contrast, Because of the dose enhancement effect with oblique incidence, The dose was gradually increased toward the obliquely tangential angle for the WT and TOMO DIRECT. Conclusion : For PMRT, TOMO DIRECT and TOMO HELICAL deliver the higher surface and superficial doses than treatment techniques based linear accelerator. It showed adequate dose(over 75% of prescribed dose) at 1mm depth in skin region.

• Radiation Oncology Journal
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• v.10 no.2
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• pp.147-153
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• 1992

It is ideal thing to compensate tissue deficit without skin contamination in curvatured irradiation field of high energy photon beam. The 3-dimensional compensating technique utilizing tissue equivalent materials to ensure an adequate dose distribution and skin sparing effect was described. This compensator was made of paraffin ($70\%$) and stearin wax ($30\%$) compound. The parameters for evaluation of the effect on skin dose in application of compensator were considered in the size of the field, the thickness of the compensator and the source-to-axis distance. The results are as follows; the skin doses were not changed even though application of the compensator, but depended on the field size and the source-to-axis distance, and the skin doses were only slightly changed within $1\%$ relative errors as increasing the thickness of the compensator in these experiments.

• Progress in Medical Physics
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• v.16 no.4
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• pp.161-165
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• 2005

The CT number corresponds to electron density and its influence on dose calculation was studied. Five kinds of CT scanners were used to obtain Images of electron density calibration phantom (Gammex RMI 467), Then the differences between CT numbers for each scanners were ${\pm}2\%$ In homogeneous medium and $9.5\%$ in high density medium. In order to Investigate the influence of CT number to dose calculation, patients' thoracic CT images were analyzed. The maximum dose difference was $0.48\%$ for each organ. It acquired the phantom Images inserted high density material in the water phantom. Comparing the doses calculated with CT Images from each CT scanner, the maximum dose difference was $2.1\%$ in 20 cm in depth. The exact density to CT number conversion according to CT scanner is required to minimize the uncertainty of dose depends on CT number Especially the each hospital with various CT scanners has to discriminate CT numbers for each CT scanner. Moreover a periodic quality assurance is required for reproducibility of CT number.

• Progress in Medical Physics
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• v.25 no.4
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• pp.255-263
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• 2014

The dosimetry of very small fields is challenging for several reasons including a lack of lateral electronic equilibrium, large dose gradients, and the size of detector in respect to the field size. The objective of this work was to evaluate the suitability of a new commercial synthetic diamond detector, namely, the PTW 60019 microDiamond, for the small field dosimetry in cyberknife photon beams of 6 different collimator size (from 5 mm to 30 mm). Measurements included dose linearity, dose rate dependence, output factors (OF), percentage depth doses (PDD) and off center ratio (OCR). The results were compared to those of pinpoint ionization chamber, diamond detector, microLion liquid Ionization chamber and diode detector. The dose linearity results for the microDiamond detector showed good linearly proportional to dose. The microDiamond detector showed little dose rate dependency throughout the range of 100~600 MU/min, while microLion liquid Ionization chamber showed a significant discrepancy of approximately 5.8%. The OF measured with microDiamond detector agreed within 3.8% with those measured with diode. PDD curves measured with silicon diode and diamond detector agreed well for all the field sizes. In particular, slightly sharper penumbras are obtained by the microDiamond detector, indicating a good spatial resolution. The results obtained confirm that the new PTW 60019 microDiamond detector is suitable candidate for application in small radiation fields dosimetry.

• Radiation Oncology Journal
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• v.20 no.1
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• pp.24-33
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• 2002

Purpose : In order to improve dose homogeneity and to reduce acute toxicity in tangential whole breast radiotherapy, we evaluated two treatment techniques using multiple static fields or universal compensators. Materials and Methods : 1) Multistatic field technique : Using a three dimensional radiation treatment planning system, Adac Pinnacle 4.0, we accomplished a conventional wedged tangential plan. Examining the isodose distributions, a third field which blocked overdose regions was designed and an opposing field was created by using an automatic function of RTPS. Weighting of the beams was tuned until an ideal dose distribution was obtained. Another pair of beams were added when the dose homogeneity was not satisfactory. 2) Universal compensator technique : The breast shapes and sizes were obtained from the CT images of 20 patients who received whole breast radiation therapy at our institution. The data obtained were averaged and a pair of universal physical compensators were designed for the averaged data. DII (Dose Inhomogeneity Index : percentage volume of PTV outside $95\~105\%$ of the prescribed dose) $D_{max}$ (the maximum point dose in the PTV) and isodose distributions for each technique were compared. Results : The multistatic field technique was found to be superior to the conventional technique, reducing the mean value of DII by $14.6\%$ (p value<0.000) and the $D_{max}$ by $4.7\%$ (p value<0.000). The universal compensator was not significantly superior to the conventional technique since it decreased $D_{max}$ by $0.3\%$ (p value=0.867) and reduced DII by $3.7\%$ (p value=0.260). However, it decreased the value of DII by maximum $18\%$ when patients' breast shapes fitted in with the compensator geometry. Conclusion : The multistatic field technique is effective for improving dose homogeneity for whole breast radiation therapy and is applicable to all patients, whereas the use of universal compensators is effective only in patients whose breast shapes fit inwith the universal compensator geometry, and thus has limited applicability.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.77-84
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• 2017

Purpose: To evaluate the image quality improvement and dosimetric effects on virtual monochromatic images of a Dual Source-Dual Energy CT(DS-DECT) for radiotherapy planning. Materials and Methods: Dual energy(80/Sn 140 kVp) and single energy(120 kVp) scans were obtained with dual source CT scanner. Virtual monochromatic images were reconstructed at 40-140 keV for the catphan phantom study. The solid water-equivalent phantom for dosimetry performs an analytical calculation, which is implemented in TPS, of a 10 MV, $10{\times}10cm^2$ photon beam incident into the solid phantom with the existence of stainless steel. The dose profiles along the central axis at depths were discussed. The dosimetric consequences in computed treatment plans were evaluated based on polychromatic images at 120 kVp. Results: The magnitude of differences was large at lower monochromatic energy levels. The measurements at over 70 keV shows stable HU for polystyrene, acrylic. For CT to ED conversion curve, the shape of the curve at 120 kVp was close to that at 80 keV. 105 keV virtual monochromatic images were more successful than other energies at reducing streak artifacts, which some residual artifacts remained in the corrected image. The dose-calculation variations in radiotherapy treatment planning do not exceed ${\pm}0.7%$. Conclusion: Radiation doses with dual energy CT imaging can be lower than those with single energy CT imaging. The virtual monochromatic images were useful for the revision of CT number, which can be improved for target coverage and electron densities distribution.