• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.377-382
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• 1994

In the conventional Fourier imaging method in MRI (Magnetic Resonance Imaging), intramotion such as pulsatile flow makes zipper-like artifact along the phase encoding direction. On the other hand, line-integral projection reconstruction (LPR) method has advantages such as imaging of short T2, object and reduction of the flow artifact by elimination of the flow-induced phase fluctuation. The LPR, however, necessarily requires time consuming filtering and back-projection processes, so that the reconstruction takes long time. To overcome the long reconstruction time of the LPR and to obtain the flow artifact reduction effect, we adopted phase corrected concentric square raster sampling (CSRS) method and improved its imaging performance. The CSRS is a fast reconstruction method which has the same properties with the LPR. In this paper, we proposed a new method of flow artifact reduction using the CSRS method. Through computer simulations and experiments, we verified that the proposed method can eliminate phase fluctuations, thereby reducing the flow artifact and re- markably shorten the reconstruction time which required long time in the LPR.

• 대한의용생체공학회:의공학회지
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• 제22권3호
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• pp.223-229
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• 2001

In this paper, we have compared the direct fan-beam reconstruction method with the rebinning method in terms of computation time and spatial resolution using computer simulation. As a result, the direct fan-beam method is superior to the rebinning method in the spatial resolution though the former needs longer computation time. However, if we adopt the quarter-detector-offset technique to improve the spatial resolution, the rebinning method outperforms the direct fan-beam method. The computation times have been evaluated using the fast algorithms optimized to reduce the number of interpolation calculations at the back-projection, and the spatial resolutions have been compared using the computer generated phantoms.

• Archives of Plastic Surgery
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• 제33권1호
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• pp.101-106
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• 2006

Nipple reconstruction is an important step in breast reconstruction after mastectomy. The authors' preferred reconstructive technique is the local C-V flap in case that a small opposite nipple is not adequate for composite graft. This flap produces an excellent reconstruction, but it is not easy to produce an adequate projection and firmness of the nipple. This article describes the technique and experience in nine patients treated over two years with dermis(scar tissue) graft for nipple reconstruction. This is the first report of application of autologous dermis(scar tissue) grafting to reconstruct a nipple primarily after breast mound reconstruction, decreasing the absorption of the reconstructed nipple and increasing the hardness. The dermis(scar tissue) is taken from scar revision and/or dog-ear correction in the second stage operation after free TRAM flap breast reconstruction. And the dermis(scar tissue) graft is inserted vertically between the local flaps and horizontally under the reconstructed nipple base. Between September 2002 and February 2005, nine patients underwent C-V flap with dermis(scar tissue) graft as a part of their nipple reconstruction. The patient's ages ranged from 28 to 55 years old (mean, 41.1 years old). The follow-up period ranged from 5 to 35 months, with an average of 14.5 months. None of the nipples showed skin flap necrosis or local infection, and uneventful wound healing. Our result showed good nipple projection with less absorption and enough firmness. Our experiences shows that dermis(scar tissue) grafts in C-V flap is a very useful method for nipple reconstruction.

• Current Optics and Photonics
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• 제5권5호
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• pp.562-575
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• 2021

As a new type of spectrometer, that based on filters with different transmittance features attracts a lot of attention for its advantages such as small-size, low cost, and simple optical structure. It uses post-processing algorithms to achieve target spectrum reconstruction; therefore, the performance of the spectrometer is severely affected by noise. The influence of noise on the spectral reconstruction results is studied in this paper, and suggestions for solving the spectral reconstruction problem under noisy conditions are given. We first list different spectral reconstruction methods, and through simulations demonstrate that these methods show unsatisfactory performance under noisy conditions. Then we propose to apply the gradient projection for sparse reconstruction (GRSR) algorithm to the spectral reconstruction method. Simulation results show that the proposed method can significantly reduce the influence of noise on the spectral reconstruction process. Meanwhile, the accuracy of the spectral reconstruction results is dramatically improved. Therefore, the practicality of the filter-based spectrometer will be enhanced.

• Radiation Oncology Journal
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• 제35권3호
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• pp.274-280
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• 2017

Purpose: To see the gross tumor volume (GTV) dependency according to the phase selection and reconstruction methods, we measured and analyzed the changes of tumor volume and motion at each phase in 20 cases with lung cancer patients who underwent image-guided radiotherapy. Materials and Methods: We retrospectively analyzed four-dimensional computed tomography (4D-CT) images in 20 cases of 19 patients who underwent image-guided radiotherapy. The 4D-CT images were reconstructed by the maximum intensity projection (MIP) and the minimum intensity projection (Min-IP) method after sorting phase as 40%-60%, 30%-70%, and 0%-90%. We analyzed the relationship between the range of motion and the change of GTV according to the reconstruction method. Results: The motion ranges of GTVs are statistically significant only for the tumor motion in craniocaudal direction. The discrepancies of GTV volume and motion between MIP and Min-IP increased rapidly as the wider ranges of duty cycles are selected. Conclusion: As narrow as possible duty cycle such as 40%-60% and MIP reconstruction was suitable for lung cancer if the respiration was stable. Selecting the reconstruction methods and duty cycle is important for small size and for large motion range tumors.

• 한국통신학회논문지
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• 제29권3C호
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• pp.419-425
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• 2004

본 논문은 카메라로 찍은 투사 사영(Perspective Projection)의 한 영상으로부터 물체의 크기와 위치를 계산하기 위해서 3 개의 소실 점만을 사용해서 계산하는 새로운 방법을 제안한다. 우리의 접근 방법은 투사 사영의 영상으로부터 초점 거리(Focal Length), 회전 행렬(Rotation Matrix) 등의 정보들 없이 3개의 소실 점만을 가지고 계산하는 방법이다. 물체는 꼭지점(vertices)의 좌표가 크기 벡터 v 의 선형 함수로서 표현할 수 있는 다각형으로써 모델이 된다는 것을 가정한다. 이 재구성의 입력은 영상에서 특징 점과 모델에서 특징 점 사이 대응점의 집합으로 표현할 수 있다. 이 매개 변수 모델의 각각 크기를 최적화하기 위해서, 재구성의 최적화는 동일하게 매개 변수 공간을 샘플링에 의한 최적화기에 대하여 다중 시작점(multiple starting points)을 발생하는 다중 시작(multi-start) 방법을 가지는 표준 비선형 최적화 기법을 효과적으로 해결할 수가 있다.

• Archives of Plastic Surgery
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• 제34권4호
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• pp.490-492
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• 2007

Purpose: Nipple reconstruction is an important step in breast reconstruction after mastectomy. There are considerable number of reconstructive methods developed over the past years. Each of these has not only its own special advantages, but also limitations. Therefore, no single method has become the overwhelming favorite. Sometimes it seems to be compromised when the nipple must be located directly over a linear scar. Methods: A 48-year-old female patient received a central lumpectomy with circumareolar resection of the nipple areolar complex 4 months ago. The newly designed nipple must be positioned directly astride a scar. We drew two equal-sized rectangular flaps sharing a common limb on a transverse scar and the result was two opposing plow form. Each flap size was about 1.3 cm wide and 2.5 cm long. First we elevated the flap from the distal part at a deep dermal plane, then deepened the level of dissection to raise the dermal-fat flaps. The donor site could be closed directly without any dog-ear deformity. Then we folded down the elevated flaps and loosely sutured skin with nonabsorbable materials. Each flap inner side was approximated side by side. Finally we made new natural nipple with 6 mm projection. We applied tattooing in the areola area with micropigmentation device after three months. Results: After ten months of follow-up periods, the nipple projection was stable and symmetric. The nipple projection was 3.1 mm, compared with 2.8 mm for the opposite nipple. Conclusion: Our experiences shows that this double opposing plow flap is a particularly useful and simple technique when there is a traverse scar crossing the center of the proposed nipple area.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1979년도 하계 전자.전기연합학술발표회논문집
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• pp.155-157
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• 1979

The Fourier convolution algorithms are used to reconstruct a 3-D density function from the projection data sets. The convolved data are then back projected to obtain a density function. There are several choices of the weighting function for the design of the reconstruction(deblurring) filter. Present paper reviews the design of reconstruction filter considering the problems such as the effects of sampling rate, aliasing, and noise.

• Archives of Plastic Surgery
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• 제46권4호
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• pp.324-329
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• 2019

Background Multiple approaches for nipple reconstruction exist, and none is considered superior to all others. The star flap is one of the most popular methods for nipple reconstruction, but gradual height loss is a major concern. We present a new modification of the star flap that incorporates a de-epithelialized dermal flap, along with the associated surgical results. Methods We reviewed the medical records of patients who underwent nipple reconstruction using the modified star flap method. The design was different from the conventional star flap in that the lateral wings were changed into a trapezoidal shape and de-epithelialized dermal flaps were added. The patients were followed up at 2, 4, 6, and 12 months postoperatively, and nipple height was measured. The postoperative nipple height achieved using the modified method was compared with that obtained using the traditional method. Results From February 2013 to June 2017, 32 patients received surgery using the modified star flap, and 18 patients who underwent nipple reconstruction before 2013 comprised the conventional method group. All patients had undergone breast reconstruction with an abdominal tissue-based flap. The mean follow-up period was 14.4 months in the modified method group and 17.3 months in the conventional method group. The mean maintenance of projection at 12 months postoperatively was $56.28%{\pm}18.58%$ in the modified method group, and $44.23%{\pm}14.15%$ in the conventional method group. This difference was statistically significant (P<0.05). Conclusions The modified method using a de-epithelialized dermal flap provides reliable maintenance of projection in patients who have undergone abdominal tissue-based breast reconstruction.

• Korean Journal of Radiology
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• 제23권7호
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• pp.752-762
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• 2022

Objective: To compare a deep learning-based reconstruction (DLR) algorithm for pediatric abdominopelvic computed tomography (CT) with filtered back projection (FBP) and iterative reconstruction (IR) algorithms. Materials and Methods: Post-contrast abdominopelvic CT scans obtained from 120 pediatric patients (mean age ± standard deviation, 8.7 ± 5.2 years; 60 males) between May 2020 and October 2020 were evaluated in this retrospective study. Images were reconstructed using FBP, a hybrid IR algorithm (ASiR-V) with blending factors of 50% and 100% (AV50 and AV100, respectively), and a DLR algorithm (TrueFidelity) with three strength levels (low, medium, and high). Noise power spectrum (NPS) and edge rise distance (ERD) were used to evaluate noise characteristics and spatial resolution, respectively. Image noise, edge definition, overall image quality, lesion detectability and conspicuity, and artifacts were qualitatively scored by two pediatric radiologists, and the scores of the two reviewers were averaged. A repeated-measures analysis of variance followed by the Bonferroni post-hoc test was used to compare NPS and ERD among the six reconstruction methods. The Friedman rank sum test followed by the Nemenyi-Wilcoxon-Wilcox all-pairs test was used to compare the results of the qualitative visual analysis among the six reconstruction methods. Results: The NPS noise magnitude of AV100 was significantly lower than that of the DLR, whereas the NPS peak of AV100 was significantly higher than that of the high- and medium-strength DLR (p < 0.001). The NPS average spatial frequencies were higher for DLR than for ASiR-V (p < 0.001). ERD was shorter with DLR than with ASiR-V and FBP (p < 0.001). Qualitative visual analysis revealed better overall image quality with high-strength DLR than with ASiR-V (p < 0.001). Conclusion: For pediatric abdominopelvic CT, the DLR algorithm may provide improved noise characteristics and better spatial resolution than the hybrid IR algorithm.