• 한국방사선학회논문지
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• 제13권5호
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• pp.773-778
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• 2019

X-선을 이용한 영상은 진단에 필수적인 요소지만 영상에서의 noise발생이 불가피하다. 이를 보완하기 위해 환자의 피폭선량은 낮추면서 영상의 질은 높여주는 total variation (TV) 알고리즘이 제시되었다. 본 연구의 목적은 시뮬레이션을 통해 부가 여과판의 두께에 따라 방사선 영상 촬영 시 영상의 화질에 미치는 영향을 확인하고, TV 알고리즘의 유용성을 평가하는 것이다. 부가 여과판의 두께변화에 따른 각 알고리즘 적용 시 Geant4 Application for Tomographic Emission (GATE) 시뮬레이션 영상을 이용하여 Polymethylmethacrylate(PMMA) 팬텀의 실제 크기, 모양과 재질을 동일하게 하고 대조도 대 잡음비 (contrast to noise ratio, CNR)과 변동계수 (coefficient of variation, COV)값을 비교하였으며 그 결과 TV 알고리즘 적용 시 CNR 값이 가장 높고 COV 값이 가장 낮다는 것을 확인할 수 있었다. 또한, 모든 알고리즘에서 0 mmAl을 사용할 경우 가장 우수한 CNR과 COV값을 얻을 수 있었다.

• 한국소음진동공학회논문집
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• 제18권7호
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• pp.701-710
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• 2008

Including a TV set and a monitor, personal audio system is raising a great interest. In this study, we applied a method to make a good bright zone around the user and dark zone to other region by maximizing the ratio of sound energy between the bright and dark zone. It has been well known as acoustic contrast control. We have attempted to use a line loudspeaker array system to localize the sound in our listening zone. It depends on the size of the zone and array parameters, for example, array size, loudspeaker unit spacing, wave length of sound. We have considered these parameters as spatial variables and studied the effects. And we have found that each spatial variable has its own characteristic and shows very different effect. Genetic algorithms are introduced to find out the optimum value of spatial variables. As a result, we can improve the result of the acoustic contrast control by optimum value of spatial variables.

• 대한방사선기술학회지:방사선기술과학
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• 제40권4호
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• pp.589-594
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• 2017

본 연구의 목적은 뇌 컴퓨터단층검사 시 양자잡음제거(Quantum Denoising System; QDS) 알고리즘을 적용한 영상 분석을 통해 화질 향상 효과를 알아보고자 한다. 2017년 7월부터 2017년 10월까지 경북 소재 G 영상의학과에 뇌 컴퓨터단층검사를 위해 내원한 45명의 성인을 대상으로 동의하에 후향적 연구를 하였고, 뇌 컴퓨터단층검사 시 QDS(-)를 적용하지 않은 그룹(A Group)과 QDS(+)를 적용한 그룹(B Group)으로 나누어 검사하였다. 다음과 같은 결론을 얻었다. 노이즈값은 Pons부분과 Vermis부분 모두 QDS(+)를 적용한 B그룹에서 통계적으로 유의하게 낮았다(A Group; Pons $6.92{\pm}0.98HU$, Vermis 6.72, B Group; Pons $5.41{\pm}1.05HU$, Vermis $5.28{\pm}0.73HU$ : p<0.05). SNR값은 Pons부분과 Vermis 부분 모두 QDS(+)를 적용한 B그룹에서 통계적으로 유의하게 높았다(A Group; Pons $5.21{\pm}1.28$, Vermis $6.23{\pm}1.49$, B Group; Pons $7.28{\pm}2.56$, Vermis $8.63{\pm}3.04$ : p<0.05). 결론적으로 뇌 컴퓨터단층검사 시 양자잡음제거 알고리즘을 적용한다면 영상의 노이즈 감소 및 신호 대 잡음비(SNR), 대조도 대 잡음비(CNR)를 좀 더 개선시켜 진단에 적절한 영상을 얻을 수 있을 것으로 생각된다.

• 대한방사선기술학회지:방사선기술과학
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• 제44권2호
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• pp.101-107
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• 2021

The purpose of this study was to evaluate optimal CT scan parameters to minimize patient dose to the irradiation and maintain satisfactory image quality in low-dose chest computed tomography (CT) scans. In a chest anthropomorphic phantom, chest CT scans were performed at different kVp and mA within reference of 3.4mGy in volume CT Dose Index (CTDI_vol). The following quantitative parameters had been statistically evaluated: image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and figure of merit (FOM). Nine radiographers conducted the blind test to select the optimal kVp-mA combination. Results indicated that the kVp-mA combination of 80kVp-90mA, 100kVp-50mA, 120kVp-30mA and 140kVp-30mA were obtained high SNR and CNR. The 120kVp-30mA combination offered good compromise in the FOM, which showed the quality and dose performance. In the blind test, an image of 80kVp-90mA obtained a high score with 4.7 points, and 120kVp-10mA or 140kVp-10mA with a low tube current were observed severe noise and poor image quality, thus resulting in decreased diagnostic accuracy. On the other hand, in the combination of high kVp and high mA(140kVp-90mA), the image quality was improved, but the radiation dose was also increased. the FOM value of 140kVp-90mA was lower than 120kVp-30mA. The application of appropriate scan parameters in low-dose chest CT scans produced satisfactory results in dose and image quality for the accuracy of the clinical diagnosis.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.719-722
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• 2019

Gamma-ray images generally suffer from a lot of noise because of low photon detection in the gamma camera system. The purpose of this study is to improve the image quality in gamma-ray images using a gamma camera system with a fast nonlocal means (FNLM) noise reduction algorithm with an acceleration function. The designed FNLM algorithm is based on local region considerations, including the Euclidean distance in the gamma-ray image and use of the encoded information. To evaluate the noise characteristics, the normalized noise power spectrum (NNPS), contrast-to-noise ratio (CNR), and coefficient of variation (COV) were used. According to the NNPS result, the lowest values can be obtained using the FNLM noise reduction algorithm. In addition, when the conventional methods and the FNLM noise reduction algorithm were compared, the average CNR and COV using the proposed algorithm were approximately 2.23 and 7.95 times better than those of the noisy image, respectively. In particular, the image-processing time of the FNLM noise reduction algorithm can achieve the fastest time compared with conventional noise reduction methods. The results of the image qualities related to noise characteristics demonstrated the superiority of the proposed FNLM noise reduction algorithm in a gamma camera system.

• 대한방사선기술학회지:방사선기술과학
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• 제41권2호
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• pp.123-128
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• 2018

Recently, the use of contrast agents has been increasing as a broader range of tests and dynamic tests have become common due to the development of equipment and imaging techniques such as Multi-Detector CT. However, the side effects of using contrast agents have been reduced by the development of non-ionic contrast agents, but they are still occurring often. The purpose of this study was to propose a method to minimize the side effect of contrast agent by using the amount of contrast agent injected to the brain angiography test to suppress excessive use of contrast agent and analyze the amount of contrast agent. Patients who were prescribed Brain Angiography due to cerebrovascular disease, According to the results of the comparison of the results obtained by dividing into 4 groups of 10ml each according to the amount of contrast medium injected with contrast agent according to the BMI of the patient, BA and SNR were not different between groups, and even if the amount of contrast injection was reduced, there was no problem in the evaluation of CT angiography through 3D reconstruction. This result shows that even if the contrast medium is injected into the blood vessels of the patient first and then the contrast medium is used as the physiological saline solution, the contrast medium is reduced by 40% it can be expected to minimize.

• Journal of Magnetics
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• 제21권4호
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• pp.593-598
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• 2016

In order to reduce the amount of noise component in X-ray imaging system, various reduction techniques were frequently used in the field of diagnostic imaging. Although the previous techniques -such as median, Wiener filters and Anscombe noise reduction technique - were able to reduce the noise, the edge information was still damaged. In order to cope with this problem, total variation (TV) noise reduction technique has been developed and researched. The purpose of this study was to evaluate and compare the image quality using normalized noise power spectrum (NNPS) and contrast-to-noise ratio (CNR) through simulations and experiments with respect to the above-mentioned noise reduction techniques. As a result, not only lowest NNPS value but also highest CNR values were acquired using a TV noise reduction technique. In conclusion, the results demonstrated that TV noise reduction technique is proved as the most practical method to ensure accurate denoising in X-ray imaging system.

• 한국방사선학회논문지
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• 제18권1호
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• pp.27-36
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• 2024

본 연구에서는 갑상샘 신티그래피 영상 획득 시 평행다공형 조준기를 적용해보고 각 영상획득 조건에서 바늘구멍형 조준기와의 차이를 정량적으로 분석해보고자 하였다. 이를 위해 갑상샘 팬텀과 점 선원을 이용하여 육안상 크기와 해상력, 민감도, 신호 대 잡음비(Signal to Noise Ratio, SNR), 대조도 대 잡음비(Contrast to Noise Ratio, CNR)를 평가 하였다. 육안상 크기를 비교하였을 때 평행다공형 조준기 적용 시 약 2.00~2.09배 정도의 확대율을 적용해야 바늘구멍형 조준기를 적용 했을 때와 비슷한 크기의 영상을 획득할 수 있는 것을 확인할 수 있었다. 점 선원을 이용한 FWHM(mm)측정에서는 경향성이 보이지 않았고 민감도는 평행다공형 조준기에서 높은 값이 나타났다. SNR, CNR은 낮은 확대율, Matrix Size 128×128, 평행다공형 조준기를 사용하였을 때 높게 나타났다. 육안상 크기가 비슷한 영상에서는 Matrix Size가 같을 때 바늘구멍형 조준기에서 SNR, CNR이 모두 높게 나타났다. 따라서 갑상샘 신티그래피 검사시행 시 각 병원의 상황에 따라 적절한 조건을 설정하여 평행다공형 조준기를 적용한다면 장비 활용 측면과 업무 효율적인 측면에서 좋은 선택지가 될 수 있을 것으로 사료된다.

• 한국방사선학회논문지
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• 제16권5호
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• pp.553-558
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• 2022

본 연구의 목적은 혈관의 가상단색성 영상 화질을 단색성 영상과 비교하여 평가한 시뮬레이션 연구이다. 이중에너지 영상은 저에너지와 고에너지 각각 50 keV, 80 keV에서 다섯 가지 물질의 선형감약계수를 바탕으로 획득되었다. 가상단색성 영상을 합성하기 위해 가중계수가 필요하며, 가중계수를 획득하기 위해 간과 뼈를 기저 물질로 사용하였다. 가상단색성 영상은 30 keV에서 100 keV 범위의 에너지에서 합성되었다. 영상 평가는 칼슘과 조영제를 신호로, 혈액을 백그라운드로 설정하여 CNR과 noise로 평가되었다. 연구결과에 따르면, 최대 CNR을 가지는 에너지는 칼슘과 조영제에서 각각 50 keV, 60 keV였다. 최소 noise를 보이는 에너지는 칼슘, 요오드 조영제, 혈액에서 각각 70 keV, 70 keV, 60 keV였다. VM 영상은 noise를 최소화하고 CNR을 최대화하는 최적의 에너지에서의 영상을 구현할 수 있으므로 CT 검사에서 진단능 향상에 기여할 수 있다.

• 대한의용생체공학회:의공학회지
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• 제18권2호
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• pp.113-120
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• 1997

This paper presents an optimal design for the SPECT reconstruction filter, based on a physical limit of SPECT lesion detection capability. To increase the performance of the filter on lesion detectability, the filter design was focused on increasing the local SyW ratio of a threshold lesion, that was determined by minimum detectable lesion size (MDU) from SPECT lesion detectabllity contrast-detail curve. The proposed filter showed flexible window characteristics of resolution recovery and noise smoothing for MDLSs in the resolution-limited and photon-limited regions, respectively, compennting for the relative impact of the main limitation factors on threshold detectability. The simulated results showed good adaptability of the proposed filter to the changes in physical parameters of photon counts, object contrast, and detector system resolution.