• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.7
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• pp.779-785
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• 2019

By applying an ergonomically developed Bismuth shield to the endovascular treatment of cerebral aneurysm the radiation dose of the scalp and lens from the medical radiation exposure was reduced. The enrtance surface dose was analyzed by measuring the occipital parts, bilateral temporal parts, bilateral quadriceps, and nasal tip of the developed bismuth shield using a photostimulable fluorescence dosimeter before (Group A) before use (Group B). Signal to noise ratio (SNR) and contrast to noise ratio (CNR) analysis were used to evaluate the image quality when Bismuth shielding was used. The mean entrance surface dose of A group and B group was 26.92% lower than that of A group. The analysis of CNR and SNR was the same for both Roadmap and DSA. The use of Bismuth shielding is an alternative that can reduce the radiation impairment due to temporary hair loss and other stochastic effects that may occur after cerebrovascular intervention.

• Progress in Medical Physics
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• v.25 no.3
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• pp.167-175
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• 2014

The purpose of this study is to evaluate the variation of the dose which is delivered to the patients with glottis cancer under IMRT (intensity modulated radiation therapy) by using the 3D registration with CBCT (cone beam CT) images and the DIR (deformable image registration) techniques. The CBCT images which were obtained at a one-week interval were reconstructed by using B-spline algorithm in DIR system, and doses were recalculated based on the newly obtained CBCT images. The dose distributions to the tumor and the critical organs were compared with reference. For the change of volume depending on weight at 3 to 5 weeks, there was increased of 1.38~2.04 kg on average. For the body surface depending on weight, there was decreased of 2.1 mm. The dose with transmitted to the carotid since three weeks was increased compared be more than 8.76% planned, and the thyroid gland was decreased to 26.4%. For the physical evaluation factors of the tumor, PITV, TCI, rDHI, mDHI, and CN were decreased to 4.32%, 5.78%, 44.54%, 12.32%, and 7.11%, respectively. Moreover, $D_{max}$, $D_{mean}$, $V_{67.50}$, and $D_{95}$ for PTV were increased or decreased to 2.99%, 1.52%, 5.78%, and 11.94%, respectively. Although there was no change of volume depending on weight, the change of body types occurred, and IMRT with the narrow composure margin sensitively responded to such a changing. For the glottis IMRT, the patient's weight changes should be observed and recorded to evaluate the actual dose distribution by using the DIR techniques, and more the adaptive treatment planning during the treatment course is needed to deliver the accurate dose to the patients.

• Radiation Oncology Journal
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• v.18 no.3
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• pp.182-186
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• 2000

Purpose : To determine treatment or이ecol for inoperable esophageal cancer patients, 껜e evaluated survival rate and prognostic factors. Materials and Methods : We evaluated esophageal cancer treated by curative or palliative am in KCCH from 1992 to 1996, retrospectively. Recurrent or underdose case below 40 Gy were excluded. The number of male and female were 35 and 5, respectively. Thirty-eight patients were squamous carcinoma and 2 patients were not biopsy proven. Ten patients were treated with radiation therapy and chemotherapy Median dose of radiation therapy was 59.4 Gy and the range was $40\~60$ Gy. Results : The median survival is 6.5 months and 1-year survival rate was $28.3\%$. Age, location, radiation dose and chemotherapy were not significant prognostic factors. Median survivals of patients with below stage III and over stage IVA were 7.6 and 6.2 months respectively, but it is not significant. Conclusions : The survival for esophageal cancer is very poor. For patients with curative aim, chemotherapy must be considered. For patients with palliative aim, short-term external beam radiation therapy and/or brachytherapy must be considered.

• The Korean Journal of Nuclear Medicine
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• v.30 no.1
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• pp.77-85
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• 1996

Radioiodine($^{131}I$) has been used for the treatment of Graves' hyperthyroidism since the late 1940's and is now generally regarded as the treatment of choice for Graves' hyperthyroidism who does not remit following a course of antithyroid drugs. But for the dose given, several different protocols have been described by different centers, each attempting to reduce the incidence of long-term hypothyroidism while maintaining an acceptable rate control of Graves' hyperthyroidism. Our goals were to evaluate effective half-life and predict absorbed dose in Graves' hyperthyroidism patients, therefore, to calculate and readminister radioiodine activity needed to achieve aimed radiation dose. Our data showed that the mean effective $^{131}I$ half-life for Graves' disease is 5.3 days(S.D=0.88) and mean biologic half-life is 21 days, range 9.5-67.2 days. The mean admininistered activity and the mean values of absorbed doses were 532 MBq(S.D.=254), 112 Gy (S.D.=50.9), respectively. The mean activity needed to achieve aimed radiation dose were 51MBq and marked differences of $^{131}I$ thyroidal uptake between tracer and therapy ocurred in our study. We are sure that the dose calculation method that uses 5 days thyroidal $^{131}I$ uptake measurements after tracer and therapy dose, provides sufficient data about the effective half-life and absorbed dose of $^{131}I$ in the thyroid and predict the effectiveness of $^{131}I$ treatment in Graves' hyperthyroidism.

• Journal of the Korean Society of Radiology
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• v.11 no.3
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• pp.161-169
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• 2017

The cone beam computed tomography(CBCT) which can acquire 3-dimensions images is widely used for confirmation of patient position before radiation therapy. In this study, through the simulation using the Monte Carlo technique, we will analyze the exposure dose by cone beam computed tomography and present the standardized data. For the experiment, MCNPX(ver. 2.5.0) was used and the photon beam spectrum was analyzed after Cone beam was simulated. As a result of analyzing the photon beam spectrum, the average energy ranged from 25.7 to 37.6 keV at the tube voltage of 80 ~ 120 kVp and the characteristic X-ray energy was 9, 60, 68 and 70 keV. As a result of using the water phantom, the percentage depth dose was measured, and the maximum dose appeared on the surface and decreased with depth. The absorbed dose also decreased as the depth increased. The absorbed dose of the whole phantom was 9.7 ~ 18.7 mGy. This is a dose which accounts for 0.2% of about 10 Gy, which is generally used for radiation therapy per week, which is not expected to have a significant effect on the treatment effect. However, it should not be overlooked even if it is small compared with prescription dose.

• Journal of the Korean Society of Radiology
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• v.9 no.2
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• pp.121-124
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• 2015

Digital Mammography is very important for the early diagnosis of breast cancer. but excessive radiation dose to the patient may increase the probability of occurrence of breast cancer. absorbed dose rate and signal, noise, and contrast in accordance with the change of the filter, and analyzed the signal-to-noise ratio. absorbed dose rate GE Equipment is higher than that of Siemens and Hologic. using the material of Mo / Mo was lower than the other target-filter combination. SNR of Siemens equipment is high and measured high when Mo / Mo selected, the other two devices was measured high when Mo / Rh selected. when you choose a target-filter combination our results will be a good indicator.

• Progress in Medical Physics
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• v.27 no.1
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• pp.25-30
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• 2016

The dosimetric characteristics were experimentally evaluated for electron beams from the prototype linac developed for radiotherapy units. This paper focuses on the electron beam output and energy variations as a function of electron gun heater current. The electron energy was derived from its mean and most probable energies measured by film dosimetry. The electron beam output at the maximum electron energy was measured with the plane parallel ionization chamber in water using TRS-398 dosimetry protocol. The mean energy and the most probable energy of the electron beam were 6.54~3.31 MeV and 5.94~2.80 MeV at electron gun current of 2.02~2.50 A respectively. The output dose rate for an electron beam of mean energy 6.54 MeV was 5.41 Gy/min ${\pm}1.5%$ at the reference depth in water.

• Journal of the Korean Society of Radiology
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• v.10 no.7
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• pp.495-502
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• 2016

In this study, we analyzed the effects of radiation exposure, as compared to the hematological parameters change of medical radiation workers and the public. The mean value of all hematological parameters were in the normal range. Eosin mean value of the radiation workers($2.52{\pm}1.79%$) showed that a significantly lower than the control group($2.92{\pm}1.39%$). In the comparison of the results depending on the occupation period, it showed high value that the mean of the radiation workers group WBC, platelet, Lymph, Mono, Baso. Over 20 years of radiation workers WBC, Mono showed low values and less than 10 years of radiation workers mean value of Baso showed low values, there was no statistical significance. In the comparison of the results depending on the 4 years cumulative radiation dose, Over 5.0 mSv of Radiation works RBC($4.61{\pm}0.53$ vs $4.91{\pm}0.38$), Hct($41.51{\pm}4.07$ vs $43.97{\pm}3.40$), Eosin($1.74{\pm}1.14$ vs $2.92{\pm}1.39$) showed low value, it was statistical significance. 0.5~1.0 mSv radiation exposure workers Hb ($13.93{\pm}1.75$) showed a significantly lower value than that of the control group ($14.90{\pm}1.29$).

• Progress in Medical Physics
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• v.13 no.4
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• pp.187-194
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• 2002

In this work we investigated through Monte Carlo calculations the physical characteristics of the absorbed dose from the Ir-192 source used in brachytherapy The Monte Carlo calculations were performed using the code EGS4, which was extensively modified in order to handle cylindrical sources, phantoms, and energy distributions to suit out own purpose. From the results of the calculations for the $\beta$ -rays, it was found that they contribute on the average 0.02% to The total absorbed dose in the distance range of 0.5-5.0 cm from the source. This is due to the face that, although most of the primary $\beta$ -rays are absorbed in the source and encapsulation material, the resulting low energy braking radiation from them contribute to such a distance. The absorbed dose in the encapsulation material varied on the average from 2.8% for platinum down to 1.1% for iron. The radial dose functions obtained by our Monte Carlo calculations were consistent within $\pm$3% with those of the TG-43 report for the radial distance interval 0.5-10.0 cm from the source. The user code we wrote in this work can be used for other sources of different sizes and so it can be very useful in designing and producing the sources for brachytherapy.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.117-125
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• 2021

Purpose: To purpose of this study is to find the correlation of the Set-up error according to the couch rotation and suggest additional margin setting for the GTV. Target and Method: Each scenario treatment plan was created by making the frequency of non-coplanar beams different among all beams. The set-up error value was measured by using the Exact System and the dose accuracy was evaluated by creating a re-treatment plan. Results: When the couch was rotated by 30°, 45°, 60°, and 90°, the mean of the X-axis values was measured to be 0.29 mm, 0.26 mm, 0.51 mm, and 0.08 mm, respectively. The mean of the Y-axis values was measured to be 0.75 mm, 0.5mm, 0.35 mm, and 0.29 mm, respectively. The mean of the Z-axis values was measured to be 0.5 mm, 0.28 mm, 0.22 mm, and 0.1 mm, respectively. There were dose reductions of 0.1%, 3.1%, 1.9% in D99 for 1-NC VMAT, 2-NC VMAT, and 3-NC VMAT, respectively. Conclusion: When treating with 50% or more of non-coplanar beams among total beams, image verification is required. And it is considered to make the treatment plan by adding a 1.5 mm margin to the GTV.