• Journal of information and communication convergence engineering
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• 제8권5호
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• pp.581-585
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• 2010

A grid was sandwiched between two cascaded imaging plates. Using a fan-beam X-ray tube and a single exposure scheme, the two imaging plates, respectively, recorded grid-less and grid type information of the object. Referring to the mathematical model of the Grid-less and grid technique, it was explained that the collected components whereas that of imaging plates with grid was of high together with large scattered components whereas that of imaging plate with grid was of low and suppressed scattered components. Based on this assumption and using a Gaussian convolution kernel representing the effect of scattering, the related data of the imaging plates were simulated by computer. These observed data were then employed in the developed post-processing estimation and restoration (kalman-filter) algorithms and accordingly, the quality of the resultant image was effectively improved.

• 대한한의학회지
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• 제38권2호
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• pp.78-84
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• 2017

A 73-year-old non-small cell lung cancer (NSCLC) patient admitted due to cough, sputum, and dyspnea, aggravated a week ago. She was diagnosed as pneumonia based on the assessment of inflammation markers, chest X-ray and sputum culture. Computed tomography (CT) scan was conducted to exclude malignant tumor metastasis. At the initiation of treatment, considering underlying disease and inflammation marker level, herbal medicine and antibiotics were concurrently used and antibiotics had been discontinued after 10days. Using the monotherapy of herbal medicine in the next 6 days, chest X-ray showed remarkably decreased infiltration in right middle lung and right lower lung. This case represented additional improvement of chest X-ray when treated only with herb medicine after termination of antibiotic therapy and demonstrated the possibility of applying herbal medicine in patients with limited use of antibiotics.

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.86-100
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• 2008

This article reviews the development of flat-panel detectors for digital radiography based on amorphous materials, Important design parameters and developments are described for the two main components of flat-panel detectors: the X-ray converter and the readout pixel array. This article also introduces the advanced development concepts of new detectors. In addition, the cascaded linear systems method is reviewed because it is a very powerful tool for improving the design and assessment of X-ray imaging detector systems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.3207-3209
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• 2000

X-ray CT(Computed Tomography) has been a good modality for non-invasive diagnosis and recently, Conventional CT has been replaced rapidly with Spiral CT in recent. In X-ray CT, spiral scanning has various advantages such as better image quality, reduced scan time (in a single breath-hold), a lower x-ray dose. But, it requires very fast and high performance image processing system to reconstruct slice images from spiral scanning. This paper describes the fast image reconstruction techniques with filtered back projection from the viewpoints of fast algorithm as well as hardware implementation for real-time imaging.

• Imaging Science in Dentistry
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• 제37권2호
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• pp.69-77
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• 2007

Purpose: To evaluate the accuracy of the imaging reformation of cone beam computed tomography for the assessment of bone defect healing in rat model. Materials and Methods: Sprague-Dawley strain rats weighing about 350 gms were selected. Then critical size bone defects were done at parietal bone with implantation of collagen sponge. The rats were divided into seven groups of 3 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 6 weeks, and 8 weeks. The healing of surgical defect was assessed by multi planar reconstruction (MPR) images and three-dimensional (3-D) images of cone beam computed tomography, compared with soft X-ray radiograph and histopathologic examination. Results: MPR images and 3-D images showed similar reformation of the healing amount at 3 days, 1 week, 2 weeks, and 8 weeks, however, lower reformation at 3 weeks, 4 weeks, and 6 weeks. According to imaging-based methodologies, MPR image revealed similar reformation of the healing amount than 3-D images compare with soft X-ray image. Among the four threshold values for 3-D images, 400-500 HU revealed similar reformation of the healing amount. Histopathologic examination confirmed the newly formed trabeculation correspond with imaging-based methologies. Conclusion: MPR images revealed higher accuracy of the imaging reformation of cone beam computed tomography and cone beam computed tomography is a clinically useful diagnostic tool for the assessment of bone defect healing.

• 대한방사선기술학회지:방사선기술과학
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• 제41권6호
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• pp.545-552
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• 2018

The purpose of this study was evaluated the relationship between echocardiography and cardiac computed tomography in normal adults by visual assessment, and evaluated the effective doses of cardiac computed tomography. The subjects were 100 normal patients who visited two general hospitals in Chungnam, from January 1 to May 30, 2018. We obtained images by using these modalities and evaluated the wall thickness and internal dimension of the Left Ventricle with visual assessment. To evaluate the appropriateness of the visual evaluation, two evaluators who were trained for one week were measured and the agreement between the evaluators were verified by statistical analysis. The effective doses of computed tomography were evaluated using the dose length product. As a result, there was a high correlation between the two modalities. The agreement between the two visual evaluator were also highly agreed. The mean X-ray dose of the subjects was $11.1{\pm}3.1mSv$. Although the purpose of imaging is somewhat different in the clinical setting, echocardiography could achieve the same results as radiation-invasive computed tomography. It is thought that utilization will become even larger.

• 한국CDE학회논문집
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• 제16권4호
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• pp.285-291
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• 2011

A pose estimation process from medical images is calculating locations and orientations of objects obtained from Computed Tomography (CT) volume data utilizing X-ray images from two directions. In this process, digitally reconstructed radiograph (DRR) images of spatially transformed objects are generated and compared to X-ray images repeatedly until reasonable transformation matrices of the objects are found. The DRR generation and image comparison take majority of the total time for this pose estimation. In this paper, a fast DRR generation technique based on GPU parallel computing is introduced. A volume ray-casting algorithm is explained with brief vector operations and a parallelization technique of the algorithm using Compute Unified Device Architecture (CUDA) is discussed. This paper also presents the implementation results and time measurements comparing to those from pure-CPU implementation and open source toolkit.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.319-321
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• 2004

The average glandular dose (AGD) is determined by the breast entrance skin exposure, x-ray tube target material, beam quality (half-value layer), breast thickness, and breast composition. Almost breast cancer always arises in glandular breast tissue. As a result, the average radiation absorbed dose to glandular tissue is the preferred measure of the radiation risk associated with mammography. If the normalized average glandular dose is known, the average glandular dose can be computed from the product of the normalized average glandular dose and breast entrance skin exposure. In this study, AGD was calculated by the breast thickness and various x-ray energy (HVL) in 50% glandular 50% adipose breast by Mo.-Rh. assembly. AGD is 84 mrad in compressed 5 cm breast. These results show that as increasing the breast thickness, dose also increases. But as increasing the x-ray tube voltage, dose decreases because of high penetrating ratio through the object. But high tube voltage is reducing the subject contrast. From this result, we have to consider the trade-off between subject contrast of image and dose to the patient and choose proper x-ray energy range.

• 지질공학
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• 제24권3호
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• pp.353-362
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• 2014

다공질 암석의 공극구조는 그 암석의 수리-역학적 거동에 매우 큰 영향을 미친다. 다공질 암석의 공극구조 특성을 표현하는 대표적인 방법은 공극률, 공극크기분포, 방향성 등이 있다. 암석의 유효공극률은 실험적으로 비교적 쉽게 구할 수 있지만, 공극의 크기분포 특성을 파악하는 것은 매우 어려운 실정이다. 본 연구에서는 X-ray CT를 이용하여 대표적 다공질 암석인 베레아 사암의 공극구조 중 공극크기분포를 이미지 기반으로 평가하였다. 공극크기분포 평가를 위해 본 연구에서는 이미지 필터링, 이진화, 골격화 등의 이미지 기반 처리 작업을 수행하였으며, 국부 두께평가 및 star chord를 이용하여 베레아 사암의 공극크기분포를 구하였다. 본 연구에서 제시된 X-ray CT 기반의 공극크기분포 평가방법을 이용하여 향후 다공질 재료의 공극구조 평가에 새롭고 효율적인 방안을 제시하고자 하였다.

• 대한의용생체공학회:의공학회지
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• 제35권5호
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• pp.151-159
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• 2014

Computed tomography (CT) is one of the most widely used medical imaging modality. However, substantial x-ray dose exposed to the human subject during the CT scan is a great concern. Region-of-interest (ROI) CT is considered to be a possible solution for its potential to reduce the x-ray dose to the human subject. In most of ROI-CT scans, the ROI is set to a circular shape whose diameter is often considerably smaller than the full field-of-view (FOV). However, an arbitrarily shaped ROI is very desirable to reduce the x-ray dose more than the circularly shaped ROI can do. We propose a new method to make a non-circular convex-shaped ROI along with the image reconstruction method. To make a ROI with an arbitrary convex shape, dynamic collimations are necessary to minimize the x-ray dose at each angle of view. In addition to the dynamic collimation, we get the ROI projection data with slightly lower sampling rate in the view direction to further reduce the x-ray dose. We reconstruct images from the ROI projection data in the compressed sensing (CS) framework assisted by the exterior projection data acquired from the pilot scan to set the ROI. To validate the proposed method, we used the experimental micro-CT projection data after truncating them to simulate the dynamic collimation. The reconstructed ROI images showed little errors as compared to the images reconstructed from the full-FOV scan data as well as little artifacts inside the ROI. We expect the proposed method can significantly reduce the x-ray dose in CT scans if the dynamic collimation is realized in real CT machines.