• The Journal of Korean Society for Radiation Therapy
• /
• v.29 no.1
• /
• pp.57-68
• /
• 2017

Purpose: The purpose of this study was to compare volumetric modulated arc therapy(VMAT) with fixed-field intensity modulated radiation therapy(IMRT) using non-coplanar beam when the shape of target is irregular and the location is adjacent to organ at risk(OAR). Materials and Methods: The subjects of this study were a total of 6 patients who had radiation therapy for whole scalp(2 patients), partial scalp(2 patients), and whole ventricle(2 patients) by True Beam STX(Varian Medical Systems, USA). VMAT plans consisted of coplanar or non-coplanar arcs which can minimize the volume of OAR included in beamlets. All fixed-field IMRT plans consisted of non-coplanar beams using more than 2 angles of Couch. Results: The VMAT and IMRT plans were compared with regard to the maximum dose of both lens, both optic nerves, optic chiasm, and brain stem and the mean dose of both eyeballs and hippocampus. VMAT plans showed higher dose than ncIMRT plans at more than 6 of all OARs in every patient, and the ratio was from 1.1 times to 8.2 times. In case of total scalp and partial scalp, the volume of brain which received more than 20 Gy in the VMAT plans was 2 times larger than the volume in the ncIMRT plans. In case of whole ventricle, there was no significant difference. Target coverage was satisfied in both plans($PTV_{100%}=95%$). The maximum dose in target volume and required monitor unit(MU) of ncIMRT were higher than them of VMAT plans. Conclusion: Even though ncIMRT is less efficient than VMAT with regard to required MU and treatment time, the dose to OARs is much lower than VMAT and PTV Coverage is similar with VMAT. If the shape of target is irregular and location is adjacent to OAR, comparison VMAT plan with ncIMRT plan deserves to be considered.

• Archives of Plastic Surgery
• /
• v.41 no.2
• /
• pp.140-147
• /
• 2014

Background Epidermal cysts are commonly occurring masses usually less than 5 cm in diameter, but in predisposed patients, epidermal cysts can grow relatively large due to chronic infection. Methods From June 2002 to July 2010, 17 patients received 19 regional perforator-based island flaps to cover defects due to the excision of large epidermal cysts (diameter >5 cm) in the buttocks. Eight patients had diabetes, and seven had rheumatoid arthritis. The pedicles were not fully isolated to prevent spasms or twisting. Results All the flaps survived completely, except for one case with partial necrosis of the flap, which necessitated another perforator-based island flap for coverage. There were two cases of wound dehiscence, which were reclosed after meticulous debridement. There were no recurrences of the masses during follow-up periods of 8.1 months (range, 6-12 months). Conclusions In patients with large epidermal cysts and underlying medical disorders, regional perforator-based island flaps can be the solution to coverage of the defects after excision.

• Journal of Periodontal and Implant Science
• /
• v.38 no.2
• /
• pp.253-262
• /
• 2008

Background: Incomplete flap coverage or early exposure over implants and/or barrier membranes have a negative effect on bone regeneration. In cases of using regenerative techniques, complete soft tissue coverage of the implant area is necessary to promote adequate conditions for guided bone regeneration. Primary socket closure may be difficult, when periosteal releasing incision is only used, due to the opening left by extracted tooth. Therefore, Soft tissue grafting techniques are used to achieve primary soft tissue closure. Materials and Methods: Soft tissue grafting techniques, with or without barrier membranes, were performed for primary closure in four cases of immediate placements. Three different methods were used (CTG, VIP-CT, Palatal advanced flap). Clinical results of the grafting were evaluated. Result: One case showed early exposure of cover-screw and, no other complications were noted. In the others, Primary closure was achieved by soft tissue grafting techniques. One of the cases, Graft showed partial necrosis, but there were no exposure over implants and/or barrier membranes. Conclusion: The use of grafting techniques, in immediate implant placement, can predictably obtain primary closure of extraction sockets, thereby providing predictable bone formation and improved implant results.

• Korean Journal of Metals and Materials
• /
• v.46 no.5
• /
• pp.296-303
• /
• 2008

Hydrogen permeation through dense palladium-based membranes has attracted the attention of many scientists largely due to their unmatched potential as hydrogen-selective membranes for membrane reactor applications. Although it is well known that the permeation mechanism of hydrogen through Pd involves various processes such as dissociative adsorption, transitions to and from the bulk Pd, diffusion within Pd, and recombinative desorption, it is still unclear which process mainly limits hydrogen permeation at a given temperature and hydrogen partial pressure. In this study, we report an all-electron density-functional theory study of hydrogen permeation through Pd membrane (using VASP code). Especially, we focus on the variation of the energy barrier of the penetration process from the surface to the bulk with hydrogen coverage, which means the large reduction of the fracture stress in the brittle crack propagation considering Griffith's criterion. It is also found that the penetration energy barrier from the surface to the bulk largely decreases so that it almost vanishes at the coverage 1.25, which means that the penetration process cannot be the rate determining process.

• Archives of Plastic Surgery
• /
• v.49 no.6
• /
• pp.745-749
• /
• 2022

Background Soft tissue defects of the multiple finger present challenges to reconstruction surgeons. Here, we introduce the use of a lateral arm free flap and syndactylization for the coverage of multiple finger soft tissue defects. Methods This retrospective study was conducted based on reviews of the medical records of 13 patients with multiple soft tissue defects of fingers (n = 33) that underwent temporary syndactylization with a microvascular lateral arm flap for temporary syndactylization from January 2010 to December 2020. Surgical and functional outcomes, times of flap division, complications, and demographic data were analyzed. Results Middle fingers were most frequently affected, followed by ring and index fingers. Mean patient age was 43.58 years. The 13 patients had suffered 10 traumas, 2 thermal burns, and 1 scar contracture. Release of temporary syndactyly was performed 3 to 9 weeks after syndactylization. All flaps survived, but partial necrosis occurred in one patient, who required a local transposition flap after syndactylization release. The mean follow-up was 15.8 months. Conclusion Coverage of multiple finger defects by temporary syndactylization using a free lateral arm flap with subsequent division offers an alternative treatment option.

• Journal of Korean Foot and Ankle Society
• /
• v.24 no.4
• /
• pp.148-155
• /
• 2020

Purpose: Minor foot amputations are performed for recurrent or infected ulcers or osteomyelitis of the diabetic feet. Patients may require a large amount of bone resection for wound closure. On the other hand, this results in more foot dysfunction and a longer time to heal. The authors describe fillet flap coverage to avoid more massive resection in selected cases. This study shows the results of fillet flap coverage for the closure of diabetic foot minor amputation. Materials and Methods: This was a retrospective case series of patients who underwent forefoot and midfoot amputation and fillet flap for osteomyelitis or nonhealing ulcers between March 2013 to November 2017. In addition, the patient comorbidities, hospital days, complications, and duration to complete healing were evaluated. Results: Fourteen fillet flap procedures were performed on 12 patients. Of those, two had toe necrosis, nine had forefoot necrosis, and three had midfoot necrosis. Eleven forefoot amputations and three midfoot amputations were performed. Among forefoot necrosis after a fillet flap, three patients had revision surgery for partial necrosis of the flap, and two patients had an additional amputation. Two patients had additional amputations among those with midfoot necrosis. By the fillet flap, the amputation size was reduced as much as possible. The mean initial healing days, complete healing days, and hospital stay was 70.6 days, 129.0 days, and 60.0 days, respectively. Conclusion: The fillet flap facilitates restoration of the normal foot contour and allows salvage of the metatarsal or toe.

• Archives of Plastic Surgery
• /
• v.48 no.4
• /
• pp.395-403
• /
• 2021

Background Groin wounds occurring after vascular surgical site infection, oncologic resection, or occasionally orthopedic surgery and trauma may represent a surgical challenge. Reconstruction of these defects by the usual workhorse flaps may be contraindicated following previous surgery and in patients with lower limb lymphedema or extreme morbidity. Methods This study included 15 consecutive patients presenting with inguinal wounds after vascular or general surgery that required debridement and soft tissue coverage. All cases had absolute or relative contraindications to conventional reconstructive techniques, including a compromised deep femoral artery network, limb lymphedema, scarring of potential flap harvesting sites, or poor overall condition. Abdominal adipocutaneous excess enabled the performance of adipocutaneous advancement flaps in an abdominoplasty-like fashion. Immediate and long-term outcomes were analyzed. Results Soft tissue coverage was effective in all cases. Two patients required re-intervention due to flap-related complications (venous congestion and partial flap necrosis). All patients fully recovered over a mean±standard deviation follow-up of 2.4±1.5 years. Conclusions Abdominal flaps can be an effective and simple alternative technique for inguinal coverage with reproducible outcomes. In our experience, the main indications are a compromised deep femoral artery network and poor thigh tissue quality. Relative contraindications, such as previous open abdominal surgery, should be considered.

• Archives of Plastic Surgery
• /
• v.48 no.1
• /
• pp.121-126
• /
• 2021

Background Despite the wide demand for thin flaps for various types of extremity reconstruction, the thin elevation technique for anterolateral thigh (ALT) flaps is not very popular because of its technical difficulty and safety concerns. This study proposes a novel perforator-centralizing technique for super-thin ALT flaps and analyzes its effects in comparison with a skewed-perforator group. Methods From June 2018 to January 2020, 41 patients who required coverage of various types of defects with a single perforator-based super-thin ALT free flap were enrolled. The incidence of partial necrosis and proportion of the necrotic area were analyzed on postoperative day 20 according to the location of superficial penetrating perforators along the flap. The centralized-perforator group was defined as having a perforator anchored to the middle third of the x- and y-axes of the flap, while the skewed-perforator group was defined as having a perforator anchored outside of the middle third of the x- and y-axes of the flap. Results No statistically significant difference in flap thickness and dimension was found between the two groups. The arterial and venous anastomosis patterns of patients in both groups were not significantly different. Only the mean partial necrotic area showed a statistically significant difference between the two groups (centralized-perforator group, 3.4%±2.2%; skewed-perforator group, 15.8%±8.6%; P=0.022). Conclusions The present study demonstrated that super-thin ALT perforator flaps can be elevated safely, with minimal partial necrosis, using the perforator-centralizing technique.

• Journal of Communications and Networks
• /
• v.12 no.5
• /
• pp.433-441
• /
• 2010

Multihop transmission is a promising technique that helps in achieving broader coverage (excellent network connectivity) and preventing the impairment of wireless channels. This paper proposes a cluster-based multihop wireless network that makes use of the advantages of multihop relaying, i.e., path loss gain, and partial relay selection in each hop, i.e., spatial diversity. In this partial relay selection, the node with the maximum instantaneous channel gain will serve as the sender for the next hop. With the proposed protocol, the transmit power and spectral efficiency can be improved over those in the case of direct transmission and conventional multihop transmission. Moreover, at a high signal-to-noise ratio (SNR), the performance of the system with at least two nodes in each cluster is dependent only on the last hop and not on any of the intermediate hops. For a practically feasible decode-and-forward relay strategy, a compact expression for the probability density function of the end-to-end SNR at the destination is derived. This expression is then used to derive closed-form expressions for the outage probability, average symbol error rate, and average bit error rate for M-ary square quadrature amplitude modulation as well as to determine the spectral efficiency of the system. In addition, the probability of SNR gain over direct transmission is investigated for different environments. The mathematical analysis is verified by various simulation results for demonstrating the accuracy of the theoretical approach.

• The Journal of Korean Academy of Prosthodontics
• /
• v.60 no.4
• /
• pp.412-419
• /
• 2022

For treatment of partially edentulous patients, a treatment using implant is widely used. Treatment method using implant are implant fixed prostheses and removable partial dentures, and for patients with severe bone resorption, removable implant overdenture with the effects of aesthetic and reducing cost can be used as treatment options. Specially, prosthesis with milled-bar and attachment has the effect of being splinted between implant fixtures, higher retention and stability than conventional removable partial denture. And it has the effect of improvement of aesthetic through lip support by denture base. In this case, the patient with severe alveolar bone resorption and partial edentulous maxilla and mandible was treated by implant-assisted removable partial denture using Milled-bar and ADD-TOC attachment. The esthetic was improved by removing the clasp because of effects of additional retention by using the attachment, and reducing palatal coverage of implant-assisted removable partial denture. The clinical results were satisfactory on the aspect of aesthetic and masticatory function.