• Journal of the Korean Society of Radiology
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• v.10 no.6
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• pp.381-385
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• 2016

This study aims to propose a method for reducing radiation dose in high-voltage radiography using air gap technique while maintaining the same image quality as when using grids. For an experiment, air gaps were set at 10 cm, 15 cm, 20 cm, 25 cm, and 30 cm with a focus-receptor distance of 180 cm; with each air gap distance, tube current was set at 15 mAs, and tube voltage was set at 80 kVp, 85 kVp, 90 kVp, 95 kVp and 100 kVp. Then, radiographs were taken. In a situation of employing a conventional method of using grids, radiographs were taken at 15 mAs and 107 kVp with a focus-receptor distance of 180 cm. According to the results of the experiment, the surface radiation dose from radiography using grids was 0.130 R; the surface radiation dose at a 20cm air gap was 0.124 R; PSNR between these two images was 10.65 [dB]. In conclusion, the air gap distance, which could maintain the image quality similar to that of a case where scattered radiation was removed and grids were used with a small surface radiation dose, was 20 cm. The result of this study is thought to be used as an indicator to remove surface radiation dose in radiography using air gap.

• Journal of Digital Convergence
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• v.12 no.2
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• pp.555-561
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• 2014

For five diagnostic X-ray generators (DR), four units turned out to be appropriate in tests on the reproducibility of radiation output suggested in the IEC 60601-2-54 standard, but in one unit of the X-ray equipment, an item measured in a combination of 50% of the highest tube voltage of the diagnostic X-ray equipment, the test setting of Group C with authorized output doses between $1{\mu}Gy$ and $5{\mu}Gy$ of mAs turned out to be inappropriate. As a result, the radiation dose to the IEC 60601-2-54 standard for quantification standards proposed by the radiation output from diagnostic X-ray imaging device reproducibility of performance management should be aware that an important evaluation factor.

• Journal of radiological science and technology
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• v.31 no.2
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• pp.123-127
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• 2008

Purpose: As the demand of a simple and precise method increases to evaluate the performance of the inverter type x-ray unit, we evaluated the usefulness of the recently-introduced X-ray Multi-Function Test Device (moldel : Xi (unfors)-prestige). Method: We compared the performance of X-ray Multi-Function Test Device (XMFTD) which is non-inveasive type device with the performance of Dynalyzer III that has been most widely used inveasive type measure device. Result: X-ray output dose was increased a little in the XMFTD, but both devices were below the performance evaluation standard, 0.002 in the output reproducibility. Linearity of XMFTD were below 0.1 which means that Dynalyzer III showed more excellency in linearity. As the the accuracy of exposure factor, 1.8 and 2 tube voltage, 2.01 and 2.3 tube current were measured. The exposure time was also measured by 0.01 sec ${\pm}10%$. Both devices were within the acceptance of performance evaluatioin standard. Conclusion: We proved the usefulness of X-ray Multi-Function Test Device (model: Xi (unfors)-prestige) to evaluated the performance on reproductibility and linearity of X-ray output and accuracy of exposure factor of inverter type unit.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.236-244
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• 2011

Recently, the number of interventional procedures has increased dramatically as an alternative of invasive surgical procedure. The need for the quality control program of the angiographic units has also increased, because of concerns about the increased patient dose and the importance of image quality of angiographic units for the successful procedures. The purpose of this study was to propose an optimal guideline for the quality control program of the angiographic units. We reviewed domestic and international standards about medical imaging system and we evaluated the quality of 61 angiographic units in Korea with the use of NEMA 21 phantom. According to the results of our study, we propose a guideline for the quality control program of the angiographic units. Quality control program includes tube voltage test, tube current test, HVL test, image-field geometry test, spatial resolution test, low-contrast iodine detectability test, wire resolution test, phantom entrance dose test. Proposed reference levels are as follows: PAE < $\pm$ 10% in tube voltage test, PAE < $\pm$ 15% in tube current test, minimum 2.3 mmAl at 80 kVp in HVL test, minimum 'acceptable' level at image-field geometry test, 0.8 lp/mm for detector size of 34-40cm, 1.0 lp/mm for detector size of 28-33cm, 1.2 lp/mm for detector size of 22-27cm in spatial resolution test, minimum 200mg/cc in low contrast iodine detectability test, phantom entrance dose should be under 10R/min, 0.012 inch wire should be seen at static wire resolution test, and 0.022 inch wire should be seen at moving wire resolution test.

• Journal of the Korean Society of Radiology
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• v.5 no.6
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• pp.369-375
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• 2011

In dental radiography, panoramic views cause distortion and thus may bring about inaccurate results in the process of quantitative analysis. In this connection, there has recently been an increasing use of cone beam computed tomography (CBCT) that is known to provide high-resolution images and positional information. In this study, a dental computed tomography unit, 'DCT-90-P IMPLAGRAPHY (Vatech, Korea)', was applied to 20 patients for 24 seconds respectively, with a tube voltage of 85kVp and a tube current of 7mA. The data of CBCT were three-dimensionally reconstructed by use of a computer program, and were histomorphometrically analyzed. The results showed that the diameter of mandibular canal is less distorted at a certain inclination of the mandibular body. The image tends to seem more distended in proportion to the distance between the subject and film. Also, the image tends to be affected according as it is out of focus. In conclusion, it requires that the image should be reconstructed in light of anatomic position and structure.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.571-578
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• 2017

Bubbles are generated by the boiling of the cooling water when an accident occurs in the reactor and then in order to measure the void fraction, the Optical Fiber Probe(OFP) and optical camera are used in thermal hydraulic safety research. However, such an optical method is not suitable for measuring the void fraction in a $17{\times}17$ array of fuel rods due to the geometrical limitations. This study was conducted as a preliminary study using x-ray system and various phantoms before applying to rod bundles. Through radiographic and tomographic experiments, the tube voltage of the x-ray generator was 130 kVp and the tube current was 1 mA. In addition, it is possible to measure the hole of 1mm in size visually through the bubble resolution phantom, and it is confirmed that the contrast is relatively decreased in the inside of the freon in the case of the contrast evaluation using the road phantom. However, we could obtain good image without distortion when reconstructing the image. Bubble generation phantom experiments were used to confirm the flow direction of the bubbles and to acquire tomography images. The image J tool was used to measure the void fraction of 18 % for a single tomography image. This study has carried out previous researches for the measurement of the bubble rate around the nuclear fuel and could be used as a basic research for continuous research.

• The Journal of the Korea Contents Association
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• v.10 no.5
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• pp.343-350
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• 2010

We measured the radiation exposure for 55 persons (male: 36, female: 19) who was diagnosed with kidney and ureter stones and received ESWL. The absorbed dose was measured at the organ which is expected to absorb relatively much radiation (kidney, bladder, liver). The radiation dose measurement voltage 80kVp, current of 5mA as a fixed model of the human body by using the Rando phantom with Radiophotoluminescent Glass Dosimeter. Absorbed dose was measured for two times (5 minute and 10 minute, each) and converted to effective dose. Mean number of treatment was 1.8 times (1~4) per patient was the mean time of radiation exposure533 seconds (248-2516). For the treatment of right renal stone, the effective dose of right kidney, left kidney, liver and bladder was 2.458mSv, 0.152mSv, 1.404 mSv and 0.019mSv, respectively. For the treatment of left renal stone, the effective dose of right kidney, left kidney, liver and bladder was 2.496mSv, 0.252mSv, 0.178 mSv, and 0.017mSv, respectively. For the treatment of distal ureter stone, the effective dose of right kidney, left kidney and bladder was 0.009mSv, 0.01mSv and 3.742mSv, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.374-374
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• 2014

의료용 X-ray는 과거 analog 방식과, 연구가 진행 중이며 현재 많이 사용되고 있는 digital 방식으로 나누어진다. 최근, 광도전체와 형광체 기반의 flat panel X-ray detector의 발전에 따른 상용화가 이루어지고 있으며, 많은 발전 가능성이 제기되고 있다. flat panel X-ray detector 검출방식은 direct method (직접 방식)와 indirect method (간접 방식)로 나누어진다. 본 연구는 일반적으로 상용화 되어있는 amorphous seleinum (비정질 셀레늄)의 큰 일함수에 의한 저 해상력이라는 단점을 보완하기 위해, 작은 일함수를 가지는 물질을 사용하여, 영상을 얻을 시에 높은 해상력으로 표현할 수 있도록 하고, 원자번호가 높은 물질을 사용하여 X-ray 흡수율을 높일 수 있도록 기존 direct method에 많이 사용되고 있는 amorphous seleinum 기반 digital X-ray detector가 아닌, 이러한 장점을 충족시킬 수 있는 PbI2 물질 층을 사용하여 시편을 제작 하였다. PbI2를 같은 두께로 올린 후, 물질 층 상부에 Au 전극 면적을 다른 size로 제작한 시편으로 X-ray에 노출 시켰다. 이는 상부 전극 size 차이에 따른 신호 차이를 측정하여 전기적 특성을 평가하기 위한 것이다. 전도성을 띠고 있는 ITO (Indium - Tin - Oxide) glass를 이용하여 screen printing 방법으로 제작하였다. PbI2층을 약 160~180 um두께, $3cm{\times}3cm$ size로 5개 제작하였으며, 상부 전극으로는 Au를 진공 증착 시켰다. 상부 전극 size는 각각 시편 5개에 $0.5cm{\times}0.5cm$, $1cm{\times}1cm$, $1.5cm{\times}1.5cm$, $2cm{\times}2cm$, $2.5cm{\times}2.5cm$로 PbI2 물질 층 중앙에 증착 시켰다. 이러한 설정으로 X-ray 노출 시 관찰할 수 있는 PbI2의 전기적인 특성을 평가할 수 있었다. 관전압을 40 kVp, 60 kVp, 80 kVp, 100 kVp, 120 kVp, 140 kVp로 설정하고, 관전류는 100 mA로 설정하였으며, Dark current, Sensitivity를 측정하였다. Dark current와 Sensitivity를 측정한 뒤, 그 값을 이용하여 SNR (신호 대 잡음 비)값을 구해보았다.실험 결과 단위면적당 signal과 SNR을 분석할 수 있었다. 80 kVp로 기준을 잡고 결과 값을 보면 $0.5cm{\times}0.5cm$ 시편에서 2.92 nC/cm2, $2.5cm{\times}2.5cm$ 시편에서 0.84 nC/cm2로 상부 전극 크기가 작을수록 더 좋은 신호를 측정할 수 있었다. 똑같은 기준에서 SNR을 계산 해 보았을 때, $0.5cm{\times}0.5cm$ 시편에서 6.46, $2.5cm{\times}2.5cm$ 시편에서 1.91로 SNR역시 상부 전극 크기가 작을수록 더 큰 값을 확인할 수 있었다. 이러한 결과는 edge-effect의 영향으로 인해 나온 결과라고 할 수 있다. 이러한 실험 결과, detector 제작 시, 같은 물질을 사용하여 더 높은 효율을 내기 위해서는 큰 size의 상부 전극 보다는 작은 size의 상부 전극을 증착 시키는 것이 전기적 특성을 더욱 효율적으로 평가할 수 있을 것이라고 사료된다.

• The Journal of the Korea Contents Association
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• v.15 no.6
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• pp.290-296
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• 2015

The purpose of this study was to derive the proposals and to suggest the exposure dose reduction scheme on pediatric head CT scan by analyzing and comparing CT dose index (CTDI) and the national diagnostic reference levels. From January 2014 to December, 231 children under 10years who were requested a pediatric head CT scan with head injury were examined. Research methods were to research and analyze the general characteristics kVp, mA test coverage $CTDI_{vol}$ and DLP referring to dose reports and electronic medical record (EMR). As a result, 7.4%(17 patients) of the total subjects in $CTDI_{vol}$ showed a national diagnostic reference levels exceeding. For DLP 41.6%(96 patients) in excess was relatively higher than $CTDI_{vol}$. DLP was exceeded more than about 60% that is higher than the CT dose index presented by Korea Food & Drug Administration. it is cause of high DLP that scan range increased more than about 30% wider than the standard test coverage presented in Health Insurance Review & Assessment Service. In conclusion, it is able to significantly lower the dose if it is complied with checking the baseline scan range of pediatric head CT scan and appropriately adjusting the protocol.

• Journal of radiological science and technology
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• v.40 no.3
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• pp.453-460
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• 2017

This study proposes effective quality control and maintenance method by developing a new qualitative evaluation method of apron for medical radiation protection. As an experimental material, one of 0.45 mm lead and 100 of 0.45 mm Pb aprons were used and irradiated under the conditions of a tube voltage of 75 kVp and a tube current of 12.5 mAs to obtain an image. and using the Image J program, PSNR values were compared and analyzed. The results showed that there were 40 aprons (less than 11dB), 55 aprons (less than 11dB, less than 30dB), and 5 aprons (30dB or more). In addition, the dose showed a normal distribution for the apron, and 5 aprons with PSNR less than 11dB and 30dB or more were selected and divided into 8 zones, and these groups were statistically significant.