• ETRI Journal
• /
• v.39 no.6
• /
• pp.841-850
• /
• 2017

We investigate neural network image reconstruction for magnetic particle imaging. The network performance strongly depends on the convolution effects of the spectrum input data. The larger convolution effect appearing at a relatively smaller nanoparticle size obstructs the network training. The trained single-layer network reveals the weighting matrix consisting of a basis vector in the form of Chebyshev polynomials of the second kind. The weighting matrix corresponds to an inverse system matrix, where an incoherency of basis vectors due to low convolution effects, as well as a nonlinear activation function, plays a key role in retrieving the matrix elements. Test images are well reconstructed through trained networks having an inverse kernel matrix. We also confirm that a multi-layer network with one hidden layer improves the performance. Based on the results, a neural network architecture overcoming the low incoherence of the inverse kernel through the classification property is expected to become a better tool for image reconstruction.

• Journal of Korean Neurosurgical Society
• /
• v.59 no.1
• /
• pp.52-57
• /
• 2016

Objective : Many surgeons advocate for watertight dural reconstruction after posterior fossa surgery given the significant risk of cerebrospinal fluid (CSF) leak. Little evidence exists for posterior fossa dural reconstruction utilizing monolayer collagen matrix onlay graft in a non-watertight fashion. Our objective was to report the results of using collagen matrix in a non-watertight fashion for posterior fossa dural reconstruction. Methods : We conducted a retrospective review of operations performed by the senior author from 2004-2011 identified collagen matrix (DuraGen) use in 84 posterior fossa operations. Wound complications such as CSF leak, infection, pseudomeningocele, and aseptic meningitis were noted. Fisher's exact test was performed to assess risk factor association with specific complications. Results : Incisional CSF leak rate was 8.3% and non-incisional CSF leak rate was 3.6%. Incidence of aseptic meningitis was 7.1% and all cases resolved with steroids alone. Incidence of palpable and symptomatic pseudomeningocele in follow-up was 10.7% and 3.6% respectively. Postoperative infection rate was 4.8%. Previous surgery was associated with pseudomeningocele development (p<0.05). Conclusion : When primary dural closure after posterior fossa surgery is undesirable or not feasible, non-watertight dural reconstruction with collagen matrix resulted in incisional CSF leak in 8.3%. Incidence of pseudomeningocele, aseptic meningitis, and wound infection were within acceptable range. Data from this study may be used to compare alternative methods of dural reconstruction in posterior fossa surgery.

• Current Optics and Photonics
• /
• v.5 no.3
• /
• pp.322-328
• /
• 2021

In this paper, a pretreatment method for a matrix in convex optimization is proposed to optimize the spectral reconstruction process of a disordered dispersion spectrometer. Unlike the reconstruction process of traditional spectrometers using Fourier transforms, the reconstruction process of disordered dispersion spectrometers involves solving a large-scale matrix equation. However, since the matrices in the matrix equation are obtained through measurement, they contain uncertainties due to out of band signals, background noise, rounding errors, temperature variations and so on. It is difficult to solve such a matrix equation by using ordinary nonstationary iterative methods, owing to instability problems. Although the smoothing Tikhonov regularization approach has the ability to approximatively solve the matrix equation and reconstruct most simple spectral shapes, it still suffers the limitations of reconstructing complex and irregular spectral shapes that are commonly used to distinguish different elements of detected targets with mixed substances by characteristic spectral peaks. Therefore, we propose a special pretreatment method for a matrix in convex optimization, which has been proved to be useful for reducing the condition number of matrices in the equation. In comparison with the reconstructed spectra gotten by the previous ordinary iterative method, the spectra obtained by the pretreatment method show obvious accuracy.

• Journal of Medicine and Life Science
• /
• v.18 no.3
• /
• pp.56-60
• /
• 2021

In recent decades, tissue engineering advances have led to more skin substitutes becoming available. Acellular dermal matrix, initially developed for use in the treatment of full-thickness burns, is made by removing the cellular components from the dermis collected from donated bodies or animals. This class of scaffold is used to replace skin and soft tissue deficiencies in a variety of fields, including breast reconstruction, abdominal wall reconstruction, and burn treatment. Herein, we provide a detailed review of the clinical applications of acellular dermal matrix.

• Archives of Plastic Surgery
• /
• v.43 no.5
• /
• pp.424-429
• /
• 2016

Background The objective of this paper was to describe a novel technique for improving the maintenance of nipple projection in primary nipple reconstruction by using acellular dermal matrix as a strut in one of three different configurations, according to the method of prior breast reconstruction. The struts were designed to best fill the different types of dead spaces in nipple reconstruction depending on the breast reconstruction method. Methods A total of 50 primary nipple reconstructions were performed between May 2012 and May 2015. The prior breast reconstruction methods were latissimus dorsi (LD) flap (28 cases), transverse rectus abdominis myocutaneous (TRAM) flap (10 cases), or tissue expander/implant (12 cases). The nipple reconstruction technique involved the use of local flaps, including the C-V flap or star flap. A $1{\times}2-cm$ acellular dermal matrix was placed into the core with O-, I-, and L-shaped struts for prior LD, TRAM, and expander/implant methods, respectively. The projection of the reconstructed nipple was measured at the time of surgery and at 3, 6, and 9 months postoperatively. Results The nine-month average maintenance of nipple projection was $73.0%{\pm}9.67%$ for the LD flap group using an O-strut, $72.0%{\pm}11.53%$ for the TRAM flap group using an I-strut, and $69.0%{\pm}10.82%$ for the tissue expander/implant group using an L-strut. There were no cases of infection, wound dehiscence, or flap necrosis. Conclusions The application of an acellular dermal matrix with a different kind of strut for each of 3 breast reconstruction methods is an effective addition to current techniques for improving the maintenance of long-term projection in primary nipple reconstruction.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.472-472
• /
• 2010

The tomography has played a key role in tokamak plasma diagnostics for image reconstruction. The Phillips-Tikhonov (P-T) regularization method was attempted in this work to reconstruct cross-sectional phantom images of the plasma by minimizing the gradient between adjacent pixel data. Recent studies about the comparison of the several tomographic reconstruction methods showed that the P-T method produced more accurate results. We have studied existing Laplacian matrix used in Phillips-Tikhonov regularization method and developed modified Laplacian matrix (Modified L). The comparison of the reconstruction result by the modified L and existing L showed that modified L produced more accurate result. The difference was significantly pronounced when a portion of plasma was reconstructed. These results can be utilized in the Edge Plasma diagnostics; especially in divertor diagnostics on tokamak a large impact is expected. In addition, accurate reconstruction results from received data in only one direction were confirmed through phantom test by using P-T method with modified L. These results can be applied to the tangentially viewing pin-hole camera diagnostics on tokamak.

• Archives of Plastic Surgery
• /
• v.49 no.1
• /
• pp.25-28
• /
• 2022

The authors performed rigid reconstruction using the sandwich technique for full-thickness chest wall defects by using two layers of acellular dermal matrix and bone cement. We assessed six patients who underwent chest wall reconstruction. Reconstruction was performed by sandwiching bone cement between two layers of acellular dermal matrix. In all patients, there was no defect of the overlying soft tissue, and primary closure was performed for external wounds. The average follow-up period was 4 years (range, 2-8 years). No major complications were noted. The sandwich technique can serve as an efficient and safe option for chest wall reconstruction.

• ETRI Journal
• /
• v.37 no.6
• /
• pp.1251-1258
• /
• 2015

We investigate an image recovery method for sparse-view computed tomography (CT) using an iterative shrinkage algorithm based on a second-order approach. The two-step iterative shrinkage-thresholding (TwIST) algorithm including a total variation regularization technique is elucidated to be more robust than other first-order methods; it enables a perfect restoration of an original image even if given only a few projection views of a parallel-beam geometry. We find that the incoherency of a projection system matrix in CT geometry sufficiently satisfies the exact reconstruction principle even when the matrix itself has a large condition number. Image reconstruction from fan-beam CT can be well carried out, but the retrieval performance is very low when compared to a parallel-beam geometry. This is considered to be due to the matrix complexity of the projection geometry. We also evaluate the image retrieval performance of the TwIST algorithm -sing measured projection data.

• Korean Journal of Head & Neck Oncology
• /
• v.35 no.1
• /
• pp.21-23
• /
• 2019

Recent studies have reported on the reconstruction of oral mucosal defects using acellular dermal matrix (ADM). This case report describes the reconstruction of a soft-palate mucosal defect using ADM. A 43-year-old man developed a $2.5cm{\times}3cm$ soft-palate mucosal defect after the removal of a lump on the soft palate andreconstructed the defect using ADM without further complications. Reconstruction of the soft palate with ADM could be more convenient than traditional methods including primary closure, skin graft, and local or free flap without complications.

• Archives of Plastic Surgery
• /
• v.46 no.6
• /
• pp.580-588
• /
• 2019

Background There are various reconstructive options for nail bed defects. However, it is challenging not to leave a deformity. In this study, we investigated differences in outcomes depending on the reconstruction method, attempted to determine which method was better, and analyzed other factors that may affect outcomes. Methods The long-term outcomes of nail bed reconstruction were reviewed retrospectively. We performed three types of reconstruction depending on the defect type: composite grafts of severed segments, nail bed grafts from the big toe, and two-stage surgery (flap coverage first, followed by a nail bed graft). Subsequent nail growth was evaluated during follow-up, and each outcome was graded based on Zook's criteria. The reconstruction methods were statistically analyzed. Other factors that could contribute to the outcomes, including age, the timing of surgery, germinal matrix involvement, defect size, and the presence of bone injuries, were also compared. Results Twenty-one patients (22 digits) who underwent nail bed reconstruction were evaluated. The type of reconstruction method did not show a significant relationship with the outcomes. However, patients who sustained injuries in the germinal matrix and patients with a defect larger than half the size of the nail bed had significantly worse outcomes than the comparison groups. Conclusions The results suggest that no operative method was superior to another in terms of the outcomes of nail bed reconstruction. Nevertheless, involvement of the germinal matrix and defect size affected the outcomes.