• Journal of the Korean Society of Radiology
• /
• v.5 no.3
• /
• pp.135-141
• /
• 2011

If protective performance of apron cannot be good, radiation exposure of an guardian or a patient, a person engaged in radiation related industry cannot rise. Therefore, It will be evaluated protection performance to radiation protection aprons by manufacturers and lead equivalent more than 0.25mm lead equivalent. And, will show in the direction of application to clinic. The new aprons by manufacturers(H, X, I, J company) and lead equivalent(0.50mmPb, 0.35mmPb, 0.25mmPb) measured transmitted dose rate and shielding rate, uniformity under fluoroscopy and general radiography using to fluoroscopy system and digital radiography system, x-ray multifunction meter. The shielding rate measurement results, 0.5mmPb apron was Shielding rate of apron of a I company(fluoroscopy : 97.96%) was the best under six companies, and shielding rate of apron of a J company(fluoroscopy : 96.25%) was worst. 0.35mmPb Apron was Shielding rate of a I company(fluoroscopy : 96.79%) was the best under the three companies, and shielding rate of an H company(fluoroscopy : 95.81%) was the worst. 0.25mmPb Apron was Shielding rate of X company apron(fluoroscopy : 90.908%) was better than H company apron(fluoroscopy : 88.82%) than two companies. The uniformity measurement results, 0.5mmPb Aprons of X company(fluoroscopy : 0.13) and I company(fluoroscopy : 0.19) was the best under the six companies, and J company apron(fluoroscopy : 0.45) was the worst. 0.35mmPb. Along a manufacturer and lead equivalent performance of apron protection is distinguished certainly. Therefore, a patient, guardian or a person engaged in radiation related industry shall enforce experiment of a lot of ways defined or evaluation so that the maximum reduces radiation exposure. Buy the apron that protective performance is good, It will be performed through experiment and evaluation.

• Journal of radiological science and technology
• /
• v.35 no.2
• /
• pp.93-102
• /
• 2012

Thanks to the rapid increase of the interest in the quality control of the General X-ray systems, this research proposes the direction of the quality control through comparing and inspecting the actual condition of the respective quality control in the Clinic, the educational institution and the hospital. The subjects of the investigation are diagnostic radiation equipment's in the clinic, the educational institution and the hospital around the capital. A test of kVp, mR/mAs out put test and reproducibility of the exposure dose, half value layer, an accordance between the light field and the beam alignment test, and lastly reproducibility of the exposure time. Then the mean difference of the percentage, the CV (Coefficient of Variation, CV) and the attenuated curve which are respectively resulted from the above tests are computed. After that we have evaluated the values according to the regulations on the Diagnostic Radiation Equipment Safety Administration regulations. In the case of the clinic and the educational institution, there were 22 general X-ray devices. And 18.2% of the kVp test, 13.6% of the reproducibility of exposure dose test, 9.1% of the mR/mAs out put test, and 13.6% of the HVL (Half Value Layer) test appeared to be improper. In the case of the hospital, however, there were 28 devices. And 7.1% of the reproducibility of exposure dose, 7.1% of the difference in the light field/ beam alignment, and 7.1% of the reproducibility of the exposure time appeared to be improper. According to the investigation, the hospital's quality control condition is better than the condition in the clinic and the educational institution. The quality control condition of the general X-ray devices in the clinic is unsatisfactory compared to the hospital. Thus, it is considered that realizing the importance of the quality control is necessary.

• The Journal of Korean Society for Radiation Therapy
• /
• v.23 no.2
• /
• pp.103-108
• /
• 2011

Purpose: Opposing portal irradiation with helmet field shape that has been given to a patient with brain metastasis can cause excess dose in patient's scalp, resulting in hair loss. For this reason, this study is to quantitatively analyze scalp dose for effective prevention of hair loss by comparing opposing portal irradiation with scalp-shielding shape and tomotherapy designed to protect patient's scalp with conventional radiation therapy. Materials and Methods: Scalp dose was measured by using three therapies (HELMET, MLC, TOMO) after five thermo-luminescence dosimeters were positioned along center line of frontal lobe by using RANDO Phantom. Scalp dose and change in dose distribution were compared and analyzed with DVH after radiation therapy plan was made by using Radiation Treatment Planning System (Pinnacle3, Philips Medical System, USA) and 6 MV X-ray (Clinac 6EX, VARIAN, USA). Results: When surface dose of scalp by using thermo-luminescence dosimeters was measured, it was revealed that scalp dose decreased by average 87.44% at each point in MLC technique and that scalp dose decreased by average 88.03% at each point in TOMO compared with HELMET field therapy. In addition, when percentage of volume (V95%, V100%, V105% of prescribed dose) was calculated by using Dose Volume Histogram (DVH) in order to evaluate the existence or nonexistence of hotspot in scalp as to three therapies (HELMET, MLC, TOMO), it was revealed that MLC technique and TOMO plan had good dose coverage and did not have hot spot. Conclusion: Reducing hair loss of a patient who receives whole brain radiotherapy treatment can make a contribution to improve life quality of the patient. It is expected that making good use of opposing portal irradiation with scalp-shielding shape and tomotherapy to protect scalp of a patient based on this study will reduce hair loss of a patient.

• Proceedings of the Korea Contents Association Conference
• /
• 2009.05a
• /
• pp.1159-1166
• /
• 2009

The use of cone-beam computed tomography(CBCT) has been proposed for guiding the delivery of radiation therapy. A kilovoltage imaging system capable of radiography, fluoroscopy, and cone-beam computed tomography(CT) has been integrated with a medical linear accelerator. A standard clinical linear accelerator, operating in arc therapy mode, and an amorphous-silicon (a-Si) with an on-board electronic portal imager can be used to treat palliative patient and verify the patient's position prior to treatment. On-board CBCT images are used to generate patient geometric models to assist patient setup. The image data can also, potentially, be used for dose reconstruction in combination with the fluence maps from treatment plan. In this study, the accuracy of Hounsfield Units of CBCT images as well as the accuracy of dose calculations based on CBCT images of a phantom and compared the results with those of using CT simulator images. Phantom and patient studies were carried out to evaluate the achievable accuracy in using CBCT and CT stimulator for dose calculation. Relative electron density as a function of HU was obtained for both planning CT stimulator and CBCT using a Catphan-600 (The Phantom Laboratory, USA) calibration phantom. A clinical treatment planning system was employed for CT stimulator and CBCT based dose calculations and subsequent comparisons. The dosimetric consequence as the result of HU variation in CBCT was evaluated by comparing MU/cCy. The differences were about 2.7% (3-4MU/100cGy) in phantom and 2.5% (1-3MU/100cGy) in patients. The difference in HU values in Catphan was small. However, the magnitude of scatter and artifacts in CBCT images are affected by limitation of detector's FOV and patient's involuntary motions. CBCT images included scatters and artifacts due to In addition to guide the patient setup process, CBCT data acquired prior to the treatment be used to recalculate or verify the treatment plan based on the patient anatomy of the treatment area. And the CBCT has potential to become a very useful tool for on-line ART.)

• Journal of radiological science and technology
• /
• v.39 no.2
• /
• pp.135-142
• /
• 2016

The purpose of this study is to evaluate propriety of using SID 180cm at Chest PA examination and to find effect of geometrical cause to the image. XGEO-GC80, INNOVISION-SH, CXDI-40EG detector and a chest phantom designed self-production was used for this study. Images were acquired at SID 180cm with changing the factor OID as 0, 75 and 83mm and were analyzed by Centricity Radiography RA1000 PACS system. Statistical program was used the SPSS (Version 22.0, SPSS, Chicago, IL, USA), p-value(under 0.05) was considered to be statistically significant. In OID 0 mm was enlarged about 2.7~3.5 mm than the actual degree of the HS, BS of phantom in all equipments. Compared with the calculated magnification has been expanded 1.6~2.8% when viewed. The OID 75 mm with OID 83 mm was extended from the CS and BS 6~8 mm range. Compared to the calculated values, the measured values are expanded from 6.1 to 7.9%. CS and BS according to the OID change showed a statistically significant difference (p<0.05) among each group, the post-analysis only OID 0 mm group appeared as an independent group, 75 mm and 83 mm are separated in the same group It was. But had no statistically significant difference could change depending on the OID (p>0.05), post-mortem analysis showed, both in the same group. Heart sizes appears larger than actual size 6~8 mm at chest PA examination which is enlarged 6.1~7.9% more than the actual theoretical value. We can find magnification of the image because of the increase of the OID due to technical limitations between cover of standing detector and the image plate. so we suggest to have occurred between them when considering the need to adjust the equipment installed by the SID to match the characteristics of the equipment.

• Radiation Oncology Journal
• /
• v.20 no.2
• /
• pp.186-192
• /
• 2002

Purpose : Measurement of transmission dose is useful for in vivo dosimetry. In this study, previous algorithm for estimation of transmission dose was modified for use in cases with tissue deficit. Materials and Methods : The beam data was measured with flat solid phantom in various conditions of tissue deficit. New algorithm for correction of transmission dose for tissue deficit was developed by physical reasoning. The algorithm was tested in experimental settings with irregular contours mimicking breast cancer patients using multiple sheets of solid phantoms. Results : The correction algorithm for tissue deficit could accurately reflect the effect of tissue deficit with errors within ${\pm}1.0\%$ in most situations and within ${\pm}3.0\%$ in experimental settings with irregular contours mimicking breast cancer treatment set-up. Conclusion : Developed algorithm could accurately reflect the effect of tissue deficit and irregularly shaped body contour on transmission dosimetry.

• Journal of Radiation Protection and Research
• /
• v.14 no.1
• /
• pp.24-33
• /
• 1989

The peripheral dose, defined as the dose outside therapeutic photon fields, was estimated for 6MV X-ray linear accelerator. The measurements were performed using silicon diode detectors controlled by automatic controlled water phantom. The effects of field size, collimator position, presence or absence of wedge filter, and wedge angle were analyzed. The results were as follows 1. The peripheral dose decreases as the distance from field margin increases and it is more than 2.4% of central axis maximum dose even at 15cm distance from field margin. 2. Maximum build-up of peripheral dose is at 2-3 mm from the water surface and drops to a minimum at 1.5cm depth and then the dose increase again. 3. The peripheral dose increases as the field size. increases. At the short distance from field margin, the difference of peripheral dose between 5 $\times\;5cm^2$ and 20 $\times\;20cm^2$ field size reaches more than 2 fold. 4. The peripheral dose is higher along the upper collimator than along the lower collimator. The differences is less than 1%. 5. The presence of wedge filter increases peripheral dose. And the peripheral dose is higher along the blade side of wedge filter than along the ridge side. The difference is about 3% at 5cm distance from the field margin for 15 $\times\;15cm^2$ field size and 60$^{\circ}$ wedge filter. 6. The Peripheral dose of wedge filter increases as the wedge filter angle increases and the increasing ratio is about 2 fold in 60$^{\circ}$wedge filter compared with open field.

• The Journal of Korean Academy of Prosthodontics
• /
• v.49 no.2
• /
• pp.120-127
• /
• 2011

Purpose: The purpose of this study was to examine the effects of chromium chloride addition on coloration, mechanical property and microstructure of 3Y-TZP. Materials and methods: Chromium chloride was weighed as 0.06, 0.12, and 0.25 wt% and each measured amount was dissolved in alcohol. $ZrO_2$ powder was mixed with each of the individual slurry to prepare chromium doped zirconia specimen. The color, physical properties and microstructure were observed after the zirconia specimen were sintered at $1450^{\circ}C$. In order to evaluate the color, spectrophotometer was used to analyze the value of $L^*$, $C^*$, $a^*$ and $b^*$, after placing the specimen on a white plate, and measured according to the International Commission on Illumination (CIE) standard, Illuminant D65 and SCE system. The density was measured in the Archimedes method, while microstructures were evaluated by using the scanning electron microscopy (SEM) and XRD. Fracture toughness was calculated Vickers indentation method and indentation size was measured by using the optical microscope. The data were analyzed with 1-way ANOVA test (${\alpha}$ = 0.05). The Tukey multiple comparison test was used for post hocanalysis. Results: 1. Chromium chloride rendered zirconia a brownish color. While chromium chloride content was increased, the color of zirconia was changed from brownish to brownish-red. 2. Chromium chloride content was increased; density of the specimen was decreased. 3. More chromium chloride in the ratio showed increase size of grains. 4. But the addition of chromium chloride did not affect the crystal phase of zirconia, and all specimens showed tetragonal phase. 5. The chromium chloride in zirconia did not showed statistically significant difference in fracture toughness, but addition of 0.25 wt% showed a statistically significant difference (P<.05). Conclusion: Based on the above results, this study suggests that chromium chlorides can make colored zirconia while adding in a liquid form. The new colored zirconia showed a slight difference in color to that of the natural tooth, nevertheless this material can be used as an all ceramic core material.

• Korean Journal of Mineralogy and Petrology
• /
• v.34 no.3
• /
• pp.169-176
• /
• 2021

This study aimed to fundamentally understand structural changes of zeolite under pressure and in the presence of different pressure-transmitting media (PTM) for application studies such as immobilization of heavy metal cation or CO₂ storage using pressure. High-pressure X-ray powder diffraction study was conducted on the zeolite-W (K_6.4Al_6.5Si_25.8O₆₄× 15.3H₂O, K-MER) to understand linear compressibility and the bulk moduli in different PTM conditions. Zeolite-w is a synthetic material having the same framework as natural zeolite merlinoite ((K, Ca_0.5, Ba_0.5, Na)₁₀ Al₁₀Si₂₂O₆₄× 22H₂O). The space group of the sample was identified as I4/mmm belonging to the tetragonal crystal system. Water, carbon dioxide, and silicone-oil were used as pressure-transmitting media. The mixture of sample and each PTM was mounted in a diamond anvil cell (DAC) and then pressurized up to 3 GPa with an increment of ca. 0.5 GPa. Pressure-induced changes of powder diffraction patterns were measured using a synchrotron X-ray light source. Lattice constants, and bulk moduli were calculated using the Le-Bail method and the Birch-Murnaghan equation. In all PTM conditions, linear compressibility of c-axis (𝛽^c) was 0.006(1) GPa^-1 or 0.007(1) GPa^-1. On the other hand, the linear compressibility of a(b)-axis (𝛽^a) was 0.013(1) GPa^-1 in silicone-oil run, which is twice more compressible than the a(b)-axis in water and carbon dioxide runs, 𝛽^a = 0.006(1) GPa^-1. The bulk moduli were measured as 50(3) GPa, 52(3) GPa, and 29(2) GPa in water, carbon dioxide, and silicone-oil run, respectively. The orthorhombicities of ac-plane in the water, and carbon dioxide runs were comparatively constant, near 0.350~0.353, whereas the value decreased abruptly in the silicone-oil run following formula, y = -0.005(1)x + 0.351(1) by non-penetrating pressure fluid condition.

• Applied Chemistry for Engineering
• /
• v.22 no.1
• /
• pp.21-25
• /
• 2011

In this study, anatase/brookite hybrid $TiO_2$ was prepared using different acid catalysts and microwave to improve photodegradation of organic pollutants. The methylene blue photodegradation properties of the prepared photocatalysts with different particle/crystal size and brookite fractions were investigated. Surface characteristics and particle sizes of anatase/brookite hybrid $TiO_2$ were evaluated using scanning electron microscopy (SEM) and laser diffraction particle size analyzer, respectively and crystal structures were investigated with X-ray diffraction (XRD). Methylene blue photodegradation properties were evaluated with UV-vis spectrophotometer. Anatase and anatase/brookite hybrid $TiO_2$ had less than 500 nm size of clusters and the average particle size of $6.66{\sim}6.85{\mu}m$, suggesting that types of acid catalysts did not affect the size. XRD of the prepared $TiO_2$ showed that the photocatalysts had anatase/brookite hybrid crystal structure and applying microwave did not change their crystal structure. Photodegradation of methylene blue with the prepared photocatalyst did not increased proportionally to the fraction of brookite and the crystal size and decreased when brookite fraction and the crystal size increased further. Anatase/brookite hybrid $TiO_2$ with brookite fraction of 9.4% and crystal size of 4.53 nm shows the best photodegradation activity of methylene blue.