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제한된 각도에서 단층영상 획득을 위한 역투사 후 필터링 방법
조민국,김호경,인지혜,김태우,Cho, Min-Kook,Kim, Ho-Kyung,Yin, Z-Hye,Kim, Tae-Woo 대한의용생체공학회 2008 의공학회지 Vol.29 No.1
We describe a backprojection filtering method for limited angle tomography. In order to reduce blur artifacts originated from the out-of-planes and control high-frequency noise, we employed two band-limited window functions, and which were realized by Hann filters in this study. Based on the experimentally measured data, the performance of the developed method is demonstrated by comparing with the conventional shift-and-add and filtered backprojection methods. Application of the developed method to the dental imaging has a potential to be used for the preoperative evaluation of the jaw for dental implants with much reduced patient dose instead of the conventional dental computed tomography.
Je, U.K.,Lee, M.S.,Cho, H.S.,Hong, D.K.,Park, Y.O.,Park, C.K.,Cho, H.M.,Choi, S.I.,Woo, T.H. Elsevier 2015 Nuclear Instruments & Methods in Physics Research. Vol.784 No.-
<P><B>Abstract</B></P> <P>In practical applications of three-dimensional (3D) tomographic imaging, there are often challenges for image reconstruction from insufficient sampling data. In computed tomography (CT), for example, image reconstruction from sparse views and/or limited-angle (<360°) views would enable fast scanning with reduced imaging doses to the patient. In this study, we investigated and implemented a reconstruction algorithm based on the compressed-sensing (CS) theory, which exploits the sparseness of the gradient image with substantially high accuracy, for potential applications to low-dose, high-accurate dental cone-beam CT (CBCT). We performed systematic simulation works to investigate the image characteristics and also performed experimental works by applying the algorithm to a commercially-available dental CBCT system to demonstrate its effectiveness for image reconstruction in insufficient sampling problems. We successfully reconstructed CBCT images of superior accuracy from insufficient sampling data and evaluated the reconstruction quality quantitatively. Both simulation and experimental demonstrations of the CS-based reconstruction from insufficient data indicate that the CS-based algorithm can be applied directly to current dental CBCT systems for reducing the imaging doses and further improving the image quality.</P>
조민국,김호경,윤한빈,장선영,이석,한명철 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.9
We introduce a cone-beam computed tomography with insufficient projections obtained from a limited-angle scan, the so-called digital tomosynthesis, and demonstrate its feasibility for the industrial applications by implementing to the reconstruction of internal slice images of a multilayer printed circuit board. The image reconstruction algorithm is based on the filtered-backprojection approach for the cone-beam geometry with isocentric linear motion in the scanning trajectory of the X-ray source and imaging detector pair. Although the slice image reconstructed at the plane of interest was affected by the structures outside, we could reconstruct the plane of interest with the total scan angle less than 20 degrees and 11 projections. The digital tomosynthesis is expected to be practical for industrial tomography restricted to the limited-angle scan.
Two-Level Multi-Pinhole Collimator for SPECT Imaging Using a Small-Field-of-View Gamma Camera
배재근,배승빈,이소영,이기성,김용권,정진헌,김민호,김경민 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.2
The aim of this study was to develop a high-throughput imaging method for single-photon emission computed tomography. We developed a target-oriented multi-pinhole collimator and limitedangle method for scanning small organs such as the thyroid. To maximize the resolution and the sensitivity of the collimator, we designed a two-level multi-pinhole collimator whose levels were optimized for concave body contours. One level had a center hole whereas the other had surrounding holes. The limited-angle scanning method was employed to obtain tomographic images by using the collimator located near the body contour of the target, and a corresponding image reconstruction algorithm was implemented. A small-field-of-view gamma camera was used to achieve a smaller footprint. The design of the collimator also considered the dimensions of used gamma camera. Evaluation studies were conducted using the Geant4 application for tomographic emission. The results showed the resolution of the proposed collimator to be more than twice that of the previously designed multi-pinhole collimator while maintaining the same efficiency. Given that the designed collimator can be changed by simply replacing the center hole, the suggested imaging method is suitable for studying not only the thyroid but also any organ whose diameter is less than 90 mm.