Compressed-sensing (CS)-based Digital Breast Tomosynthesis (DBT) Reconstruction for Low-dose, Accurate 3D Breast X-ray Imaging

박연옥,조효성,Uikyu Je,홍대기,이민식,박철규,조희문,최성일,구양서 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.4

In practical applications of three-dimensional (3D) tomographic techniques, such as digital breasttomosynthesis (DBT), computed tomography (CT), etc., there are often challenges for accurateimage reconstruction from incomplete data. In DBT, in particular, the limited-angle and few-viewprojection data are theoretically insufficient for exact reconstruction; thus, the use of commonfiltered-backprojection (FBP) algorithms leads to severe image artifacts, such as the loss of theaverage image value and edge sharpening. One possible approach to alleviate these artifacts mayemploy iterative statistical methods because they potentially yield reconstructed images that are inbetter accordance with the measured projection data. In this work, as another promising approach,we investigated potential applications to low-dose, accurate DBT imaging with a state-of-the-artreconstruction scheme based on compressed-sensing (CS) theory. We implemented an efficientCS-based DBT algorithm and performed systematic simulation works to investigate the imagingcharacteristics. We successfully obtained DBT images of substantially very high accuracy by usingthe algorithm and expect it to be applicable to developing the next-generation 3D breast X-rayimaging system.

Image Reconstruction for Digital Breast Tomosynthesis (DBT) by Using Projection-angle-dependent Filter Functions

박연옥,박철규,조효성,제의규,홍대기,이민식,조희문,최성일,구양서 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.5

Digital breast tomosynthesis (DBT) is considered in clinics as a standard three-dimensionalimaging modality, allowing the earlier detection of cancer. It typically acquires only 10-30 projectionsover a limited angle range of 15 − 60 with a stationary detector and typically uses acomputationally-efficient filtered-backprojection (FBP) algorithm for image reconstruction. However,a common FBP algorithm yields poor image quality resulting from the loss of average imagevalue and the presence of severe image artifacts due to the elimination of the dc component ofthe image by the ramp filter and to the incomplete data, respectively. As an alternative, iterativereconstruction methods are often used in DBT to overcome these difficulties, even though they arestill computationally expensive. In this study, as a compromise, we considered a projection-angledependentfiltering method in which one-dimensional geometry-adapted filter kernels are computedwith the aid of a conjugate-gradient method and are incorporated into the standard FBP framework. We implemented the proposed algorithm and performed systematic simulation works toinvestigate the imaging characteristics. Our results indicate that the proposed method is superiorto a conventional FBP method for DBT imaging and has a comparable computational cost, whilepreserving good image homogeneity and edge sharpening with no serious image artifacts.

꽃송이버섯 액체종균배지 및 배양조건에 따른 균사 배양 특성

이윤혜,권희민,구옥,최종인,전대훈 한국버섯학회 2018 한국버섯학회지 Vol.16 No.2

Sparassis latifolia is one of the most expensive mushrooms in Korean market owing to its high β-glucan content and immunoactivity. However, because of the long cultivation period and high contamination rates, it has low production efficiency. Therefore, we first need to establish the optimum conditions for liquid spawn production to increase its production efficiency. As a result of experiments, molasses culture medium was selected for mycelial growth. Also, the optimum sugar content for molasses and amount of aeration used were approximately 8 Brix% and 0.3~0.6 vvm, respectively. Mycelial dry weight increases, while the medium decreases, as the incubation period increases. Therefore, to achieve maximum production efficiency, the incubation period of 9 to 11 days is appropriate.

Application of a Dual-resolution Voxellation Scheme to Small ROI Reconstruction in Iterative CBCT for the Reduction of Computational Cost

이민식,조효성,제의규,홍대기,박연옥,박철규,조희문,최성일,구양서 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.9

In iterative methods for cone-beam computed tomography (CBCT) reconstruction, the use of ahuge system matrix is the primary computational bottleneck and is still an obstacle to the morewidespread use of these methods in practice. In this paper, to put iterative methods to practicalapplications, we propose a pragmatic idea, the-so-called dual-resolution voxellation scheme, for asmall region-of-interest (ROI) reconstruction in CBCT in which voxels outside the ROI are binnedwith a double resolution such as 2×2×2, 4×4×4, 8×8×8, 16×16×16, etc., and the voxel size withinthe ROI remains unchanged. In some situations of medical diagnosis, physicians are interestedonly in a small ROI containing a target diagnosis from the examined structure. We implementedan efficient compressed-sensing (CS)-based reconstruction algorithm with the proposed voxellationscheme incorporated and performed both simulation and experimental works to investigate theimaging characteristics. Our results indicate that the proposed voxellation scheme seems to beeffective in reducing the computational cost considerably for a small ROI reconstruction in iterativeCBCT, with the image quality inside the ROI not being noticeably impaired.

A New Voxellation Scheme for Iterative CBCT Reconstruction with Less Computational Cost: Polar Voxel Design of an Isosceles-triangle Shape

이민식,조효성,홍대기,제의규,박연옥,박철규,조희문,최성일,구양서 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.7

We propose a new voxellation scheme for iterative cone-beam computed tomography (CBCT)reconstruction with less computational cost. Here, the voxel configuration is designed with anisosceles-triangle shape by using polar coordinates, exploiting the rotational symmetries inherent tothe CBCT acquisition geometry and keeping the uniformity of the voxel size as well. By using polarsymmetries, we can reduce the size of the system matrix by a factor corresponding to the numberof acquired projections, which speeds up the construction of the system matrix and, thus, allowsiterative methods to be applied to practical applications within a reasonable reconstruction time. In this study, we implemented an efficient algorithm to reconstruct the system matrix based uponthe proposed voxellation scheme and incorporated it into a built-in iterative CBCT reconstructionalgorithm based the gradient-projection Barzilai-Borwein (GPBB) method, and we performed systematicsimulation works to investigate the imaging characteristics. Our results indicate that thevoxellation scheme we proposed in study seems to be effective in reducing the computational timeand the memory burden considerably.

느타리 톱밥종균 배지조성에 따른 생산성 비교

최종인,최준영,김정한,구옥,김연진,하태문,정구현,Choi, Jong-In,Choi, Jun-Yeong,Kim, Jeong-Han,Gu, Ok,Kim, Yeon-Jin,Ha, Tai-Moon,Jung, Gu-Hyun 한국버섯학회 2021 한국버섯학회지 Vol.19 No.1

느타리 종균배지재료인 미송톱밥과 미강을 대체할 수 있는 재료를 선발하기 위하여 실시하였다. 톱밥의 pH는 4.9~6.1, 총질소함량은 0.21~0.26%, 총탄소함량은 49.0~50.2%를 나타내며 조지방은 0.3~0.7%를 함유하고 있다. 종균 혼합배지의 pH는 5.3~5.9, 총질소함량은 0.65~1.11%, 총탄소함량은 47.0~49.1%를 나타내었다. C/N율은 총질소 함량이 낮은 미루나무톱밥 혼합배지에서 높게 나타났으며, 단백질 함량은 미송톱밥이 함유되어 있는 배지에서 높게 나타났다. 느타리 균사생장은 미강보다 밀기울이 포함되어 있는 배지에서 균사생장 속도가 빨랐다. 수량은 '곤지7호', '춘추2호', '흑타리', '수한1호' 순으로 높았으며, T4(미루나무톱밥:참나무톱밥:미강) 배지에서 가장 높은 생산성을 나타내었으나 처리 간 유의성이 없었다. 느타리 농가에서는 자가종균 제조 시 주변에서 손쉽게 구할 수 있는 미루나무톱밥, 참나무톱밥을 단용 및 혼용으로 이용할 수 있으며, 보관중에 품질유지가 어려운 미강 대신에 밀기울을 사용하여 종균을 제조할 수 있을 것으로 판단된다. This study was performed to find a medium material that can replace Douglas fir sawdust and rice bran in spawn media for growing spawn directly in the oyster mushroom farm. The pH range, total nitrogen source, and total carbon source of the mixed spawn medium were 5.3~5.9, 0.65~1.11%, and 47.0~49.1%, respectively. The C/N ratio was high in the mixed medium of poplar sawdust, with a low total nitrogen content. The protein content was high in the medium containing fermented Douglas fir sawdust. The mycelium growth rate was higher in the medium containing wheat bran than that in the medium containing rice bran. The highest yield per bottle was observed with poplar sawdust, oak sawdust, and rice bran mixed at a ratio of 40:40:20 (v/v/v); however, there was no significant difference observed in terms of productivity with the other treatments. Thus, when growing sawdust spawns in farms, it is efficient to use poplar sawdust, oak sawdust, and wheat bran, which are also easily available, instead of Douglas fir sawdust and rice bran.

병재배용 느타리 품종 『흑타리』의 배양온도에 따른 미발이 관계 규명

최종인,김정한,권희민,이윤혜,신복음,구옥,하태문,정구현 한국버섯학회 2020 한국버섯학회지 Vol.18 No.4

This experiment was conducted to solve the failure of fruiting body production in the bottle cultivation of the oyster mushroom cultivar ‘Heuktari’. The effects of incubation temperature on primordium formation and fruiting body yield of the oyster mushroom cultivar ‘Heuktari’ were investigated. The proper temperature for mycelium growth of ‘Heuktari’ on potato dextrose agar (PDA) medium is 23–26oC. The mycelial growth of ‘Heuktari’ was faster than that of Chunchu 2ho. During mycelial culture in sawdust medium, the temperature of the medium in the bottle initially increased, reached the highest point in the middle of the culture, and then decreased. The higher the set temperature, the shorter the incubation period. When the incubation temperatures were 20°C and 24°C, respectively, the undeveloped primordium formation rates were low (1.8% and 4.2%, respectively). However, the rate of undeveloped primordium formation increased, and the yield decreased at incubation temperatures of 16°C and 28°C. Mushroom farms that set incubation temperatures to 18°C and maintained the medium temperature at less than 28°C showed undeveloped primordium formation rates ranging between 0.3-0.8%. The rate of undeveloped primordium formation increased and the yield decreased in the farms with high incubation temperatures (above 28°C). We found that in order to reduce undeveloped primordium formation, the air inside the incubation room should be circulated continuously so that the temperature of the medium does not rise above 28°C, and dense incubation conditions should be avoided.

Volumetric Image Reconstruction in a Dental Panoramic Imaging System with a Limited-angle Zigzag Scan Geometry

홍대기,조효성,이선화,오지은,이민식,김효정,제의규,박연옥,최성일,구양서,조희문 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.2

As a continuation of our dental imaging R&D, we have proposed a novel idea that is capable of implementing cost-effective, low-dose, volumetric image reconstruction directly onto a dental panoramic imaging system. In the proposed geometry, a linear-type panoramic detector is rotated 90˚ from the orientation for panoramic imaging and scanned along a limited-angle zigzag trajectory in the axial direction to cover the whole imaging volume thickness. We used an effective reconstruction algorithm based on the total-variation (TV) minimization approach for the proposed geometry and performed systematic simulation work to demonstrate the viability of our proposed approach and its effectiveness for three-dimensional (3D) dental X-ray imaging. We have successfully reconstructed images of substantially high image accuracy from the proposed geometry and evaluated the reconstruction quality by using an image similarity metric, the universal-quality index (UQI). We expect the proposed method to be applicable to developing a cost-effective, low-dose, all-in-one dental X-ray imaging system.

Experimental Study on the Application of a Compressed-sensing (CS) Algorithm to Dental Cone-beam CT (CBCT) for Accurate, Low-dose Image Reconstruction

오지은,조효성,제의규,이민식,김효정,홍대기,박연옥,이선화,조희문,최성일,구양서 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.5

In practical applications of three-dimensional (3D) tomographic imaging, there are often challenges for image reconstruction from insufficient data. In computed tomography (CT), for example, image reconstruction from few views would enable fast scanning with reduced doses to the patient. In this study, we investigated and implemented an efficient reconstruction method based on compressed-sensing (CS) algorithm, which exploits the sparseness of the gradient image with substantially high accuracy, for accurate, low-dose dental cone-beam CT (CBCT) reconstruction. We applied the algorithm to a commercially-available dental CBCT system (Expert7<SUP>TM</SUP>, Vatech Co., Korea) and performed experimental works to demonstrate the algorithm for image reconstruction in insufficient sampling problems. We successfully reconstructed CBCT images with several undersampling data and evaluated the reconstruction quality in terms of the universal-quality index (UQI). Experimental demonstrations of the CS-based reconstruction algorithm appear to show that it can be applicable to current dental CBCT systems for reducing imaging doses and further improving the image quality.