• Korean Journal of Construction Engineering and Management
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• v.17 no.3
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• pp.32-42
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• 2016

In Korea, the absence of BIM use in existing civil structures and buildings is driving a demand for as-built BIM. As-built BIMs are often created using laser scanners that provide dense 3D point cloud data. Conventional static laser scanning approaches often suffer from limitations in their operability due to the difficulties in moving the equipment, the selection of scanning location, and the requirement of placing targets or extracting tie points for registration of each scanned point cloud. This paper aims at reducing the manual effort using a kinematic 3D laser scanning system based on graph-based simultaneous localization and mapping (SLAM) for continuous indoor mapping. The robotic platform carries three 2D laser scanners: the front scanner is mounted horizontally to compute the robot's trajectory and to build the SLAM graph; the other two scanners are mounted vertically to scan the profiles of surrounding environments. To reduce the accumulated error in the trajectory of the platform through loop closures, the graph-based SLAM system incorporates AdaBoost loop closure approach, which is particularly suitable for the developed multi-scanner system providing more features than the single-scanner system for training. We implemented the proposed method and evaluated it in two indoor test sites. Our experimental results show that the false positive rate was reduced by 13.6% and 7.9% for the two dataset. Finally, the 2D and 3D mapping results of the two test sites confirmed the effectiveness of the proposed graph-based SLAM.

• Progress in Medical Physics
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• v.18 no.3
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• pp.149-160
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• 2007

Recent advent of 64-multidetctor (MD) CT enables more coverage of Z-axis in the perfusion imaging. The purpose of this study was to evaluate the clinical usefulness of perfusion CT by using 64-MD CT in detecting the lesion in patients with acute stroke. The perfusion CT was performed by using 64-MD CT in 62 consecutive patients who were initially suspected to have subacute ischemic stroke symptoms during the period of recent 9 months. These patients had subacute stroke (n=62). CT scanning was conducted with Jog Mode which provided 16 imaging slices with 5 mm of slice thickness, and 8 cm of coverage in Z-axis. Scan interval was 1 seconds for each imaging slice and total 15 scans were repeated. After CT scanning, perfusion maps (CBV, CBF, MTT and TTP) were created at Extended Brilliance Workstation. The CBV and CBF maps showed that lesions were smaller images. While on the MTT and TTP map lesions were seen to be larger fifty-one were large than they appeared on these images. Two slices of perfusion maps obtained at the level of the basal ganglia were chosen to simulate conventional older perfusion CT with 8 cm of coverage in Z-axis. TTP and MTT maps may be clinically useful for evaluation of the penumbral zone in cases of aubacute cerebral ischemic stroke. The perfusion CT is useful in the assessment of acute stroke as an initial imaging modality.

• Archives of Plastic Surgery
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• v.37 no.5
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• pp.712-716
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• 2010

Purpose: Extensive lumbosacral defects after removal of spinal tumors have a high risk of wound healing problems. Therefore it is an effective reconstructive strategy to provide preemptive soft tissue coverage at the time of initial spinal surgery, especially when there is an instrument exposure. For soft tissue reconstruction of a lumbosacral defect, a variation of the gluteal flap is the first-line choice. However, the musculocutaneous flap or muscle flap that is conventionally used, has many disadvantages. It damages gluteus muscle and causes functional disturbance in ambulation, has a short pedicle which limits areas of coverage, and can damage perforators, limiting further surgery that is usually necessary in spinal tumor patients. In this article, we present the superior gluteal artery perforator turn-over flap that reconstructs complex lumbosacral defects successfully, especially one that has instrument exposure, without damaging the ambulatory function of the patient. Methods: A 67 year old man presented with sacral sarcoma. Sacralectomy with L5 corpectomy was performed and resulted in a $15{\times}8\;cm$ sized complex soft tissue defect in the lumbosacral area. There was no defect in the skin. Sacral stabilization with alloplastic fibular bone graft and reconstruction plate was done and the instruments were exposed through the wound. A $18{\times}8\;cm$ sized superior gluteal artery perforator flap was designed based on the superior gluteal artery perforator and deepithelized. It was turned over 180 degrees into the lumbosacral dead space. Soft tissue from both sides of the wound was approximated over the flap and this provided in double padding over the instrument. Results: No complications such as hematoma, flap necrosis, or infection occurred. Until three months after the resection, functional disturbances in walking were not observed. The postoperative magnetic resonance imaging scan shows the flap volume was well maintained over the instrument. Conclusion: This superior gluteal artery perforator turn-over flap, a modification of the conventional superior gluteal artery perforator flap, is a simple method that enabled the successful reconstruction of a lumbosacral defect with instrument exposure without affecting ambulatory function.

• Journal of radiological science and technology
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• v.26 no.3
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• pp.25-31
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• 2003

This study was performed to evaluate the usefulness of Deconvolution perfusion CT in patients with acute cerebral infarction. Nine patients with acute cerebral infarction underwent conventional CT and cerebral perfusion CT within 23 hours of the onset of symptoms. The perfusion CT scan for each patient was obtained at the levels of basal ganglia and 1cm caudal to the basal ganglia. By special imaging software, perfusion images including cerebral blood volume(CBV), cerebral blood flow(CBF), and mean transit time(MTT) maps were created. The created lesions were evaluated on each perfusion maps by 3 radiolocical technician. MTT delay time was measured in the perfusion defect lesion and symmetric contralateral normal cerebral hemisphere. Lesion sire were measured on each perfusion map and compared with the value obtained by diffusion weighted MR imaging(DWMRI). All perfusion CT maps showed the perfusion defect lesion in all patients. There were remarkable CT delay in perfusion defect lesion. In comparison of lesion size between each perfusion map and DWMRI, the lesion on CBF map was the most closely correlated with the lesion on DWMRI(7/9). The size of perfusion defect lesion on MTT map was larger than that of lesion on DWMRI, suggesting that m map can evaluate the ischemic penumbra. Deconvolution Perfusion CT maps make it possible to evaluate not only ischemic core and ischemic penumbra but also hemodynamic status in perfusion defect area. These results demonstrate that perfusion CT can be useful to the diagnosis and treatment in the patients with acute cerebral ischemic infarction.

• Archives of Reconstructive Microsurgery
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• v.5 no.1
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• pp.35-45
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• 1996

After transplantation of groin free flap was sucessed by the Daniel and Taylor in 1973, the reconstruction of plastic surgery was extensive and universal due to rapidly developement of anatomic study of the donor site and technique of microvascular surgery. The free tissue transfers is possible to be early activity and rehabilitation by one stage operation. It currently available allow transfer of specific tissue quality as bone, muscle, nerve to achieve a functional and cosmetic result as well as the most favorable secondary defect. But free flaps require critical, skillful technique and lengthy operating time. Also it has disadvantage of donor site morbity at the large tissue transfer. Authors were transferred with 107 cases in 103 patients from May 1987 to June 1996, and then we analysed free tissue transfer to acquire more increased sucess rate, satisfactory functional and cosmetic results. The sexual distribution was male prominent in 79 cases(76.7%), female in 24(23.3%) and age was variable distribution from 3 to 76 years old. The cause of defects was most prevalent in trauma of traffic and industrial accident in 51 cases(49%). The common recipient site were lower extremities in 47 cases(43.9%), upper extremities in 28 cases(26.5%), head and neck in 25 cases(23.4%), and trunk in 7 cases(6.5%). The type of transfer were free skin flaps in 46 cases(43%), free muscle or musculocutaneous flaps in 31 cases(29%), free vasculized or osteocutaneous flaps in 10 cases(9.3%), and specilized free flaps in 20 cases(18.7%). The anastomosis of artery was end to end anastomosis in 94 cases(87.9%), end to side anastomosis in 13 cases(12.1%) and all vein was end to end anastomosis. The number of anastomosed vessels were one artery one vein in 62 cases(57.9%), one artery two vein in 45 cases(42.1%) and vein graft was performed only one case. The postoperative mornitoring were used with temperature, color of flap, capillary refilling time, ultrasonogram, bone scan, doppler, and endoscopy. The reexploration was performed in 9 cases(8.4%), and then flap was loss in 3 cases(2.8%). Accordingly overall success rate was 97.2%. The postoperative complication was early vascular occlusion, hematoma, partial necrosis and late bulkiness, scarring, color dismatch etc. Therefore, free tissue transfer is the preferred method of treatment, even through conventional local and distant flaps are available.

• Journal of Korean Neurosurgical Society
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• v.43 no.6
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• pp.281-287
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• 2008

Objective : Cerebral vasospasm still remains a major cause of the morbidity and mortality, despite the developments in treatment of aneurysmal subarachnoid hemorrhage. The authors measured the utility and benefits of external lumbar cerebrospinal fluid (CSF) drainage to prevent the clinical vasospasm and its sequelae after endovascular coiling on aneurysmal subarachnoid hemorrhage in this randomized study. Methods : Between January 2004 and March 2006, 280 patients with aneurysmal subarachnoid hemorrhage were treated at our institution. Among them, 107 patients met our study criteria. The treatment group consisted of 47 patients who underwent lumbar CSF drainage during vasospasm risk period (about for 14 days after SAH), whereas the control group consisted of 60 patients who received the management according to conventional protocol without lumbar CSF drainage. We created our new modified Fisher grade on the basis of initial brain computed tomography (CT) scan at admission. The authors established five outcome criteria as follows : 1) clinical vasospasm; 2) GOS score at 1-month to 6-month follow-up; 3) shunt procedures for hydrocephalus; 4) the duration of stay in the ICU and total hospital stay; 5) mortality rate. Results : The incidence of clinical vasospasm in the lumbar drain group showed 23.4% compared with 63.3% of individuals in the control group. Moreover, the risk of death in the lumbar drain group showed 2.1 % compared with 15% of individuals in the control group. Within individual modified Fisher grade, there were similar favorable results. Also, lumbar drain group had twice more patients than the control group in good GOS score of 5. However, there were no statistical significances in mean hospital stay and shunt procedures between the two groups. IVH was an important factor for delayed hydrocephalus regardless of lumbar drain. Conclusion : Lumbar CSF drainage remains to playa prominent role to prevent clinical vasospasm and its sequelae after endovascular coiling on aneurysmal subarachnoid hemorrhage. Also, this technique shows favorable effects on numerous neurological outcomes and prognosis. The results of this study warrant clinical trials after endovascular treatment in patients with aneurysmal SAH.

• Journal of Biomedical Engineering Research
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• v.24 no.3
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• pp.217-231
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• 2003

Coded excitation with complementary Golay sequences is an effective means to increase the SNR and penetration of ultrasound imaging. in which the two complementary binary codes are transmitted successively along each scan-line, reducing the imaging frame rate by half. This method suffers from low frame rate particularly when multiple transmit focusing is employed, since the frame rate will be further reduced in proportion to the number of focal zones. In this paper. a new ultrasound imaging technique based on simultaneous multiple transmit focusing using modified orthogonal Golay codes is proposed to improve lateral resolution with no accompanying decrease in the imaging frame rate, in which a pair of orthogonal Golay codes focused at two different focal depths are transmitted simultaneously. On receive, these modified orthogonal Golay codes are separately compressed into two short pulses and individually focused. These two focused beams are combined to form a frame of image with improved lateral resolution. The Golay codes were modified to improve the transmit power efficiency (TPE) for practical imaging. Computer simulations and experimental results show that the proposed method improves significantly the lateral resolution and penetration of ultrasound imaging compared with the conventional method.

• Journal of Biomedical Engineering Research
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• v.31 no.3
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• pp.199-209
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• 2010

The locking compression plates-distal femur(LCP-DF) are being widely used for surgical management of the extra-articular complex fractures of the distal femur. They feature locking mechanism between the screws and the screw holes of the plate to provide stronger fixation force with less number of screws than conventional compression bone plate. However, their biomechanical efficacies are not fully understood, especially regarding the number of the screws inserted and their optimal configurations. In this study, we investigated effects of various screw configurations in the shaft and the condylar regions of the femur in relation to structural stability of LCP-DF system. For this purpose, a baseline 3-D finite element (FE) model of the femur was constructed from CT-scan images of a normal healthy male and was validated. The extra-articular complex fracture of the distal femur was made with a 4-cm defect. Surgical reduction with LCP-DF and bone screws were added laterally. To simulate various cases of post-op screw configurations, screws were inserted in the shaft (3~5 screws) and the condylar (4~6 screws) regions. Particular attention was paid at the shaft region where screws were inserted either in clustered or evenly-spaced fashion. Tied-contact conditions were assigned at the bone screws-plate whereas general contact condition was assumed at the interfaces between LCP-DF and bone screws. Axial compressive load of 1,610N(2.3 BW) was applied on the femoral head to reflect joint reaction force. An average of 5% increase in stiffness was found with increase in screw numbers (from 4 to 6) in the condylar region, as compared to negligible increase (less than 1%) at the shaft regardless of the number of screws inserted or its distribution, whether clustered or evenly-spaced. At the condylar region, screw insertion at the holes near the fracture interface and posterior locations contributed greater increase in stiffness (9~13%) than any other locations. Our results suggested that the screw insertion at the condylar region can be more effective than at the shaft during surgical treatment of fracture of the distal femur with LCP-DF. In addition, screw insertion at the holes close to the fracture interface should be accompanied to ensure better fracture healing.

• Journal of Gastric Cancer
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• v.1 no.3
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• pp.174-179
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• 2001

Purpose: For curative resection of recurrent gastric cancer, it is imperative that there be no unrecognized foci of tumoral disease outside the operation field. PET (positron emission tomography) with FDG (18 fluoro-2 deoxy-D-glucose) is a whole-body imaging technique that exploits the increased rate of glycolysis in tumor cells to detect disease. The authors evaluated the usefulness of FDG-PET in assessing resectability of recurrent gastric cancer. Materials and Methods: Seven patients with recurrent gastric cancer were studied with FDG-PET from December 1998 to October 2000. All FDG-PET images were interpreted in conjunction with conventional diagnostic methods. All imaging results were correlated with the pathological diagnosis and clinical outcome. Results: A final diagnosis of recurrence was obtained at 14 sites in all 7 patients by histology or clinical follow up. Locoregional recurrence, including distant metastasis, developed in 6 of 7 patients and distant recurrence in only one. FDG-PET detected all recurrent sites (5 locoregional and 5 distant) in 5 patients without peritoneal recurrence, but did not detect peritoneal seeding in 2 patients with peritoneal recurrence. The accuracy of FDG-PET in estimating resectability was $71.4\%$ (5/7), and that of CT and PET together was $85.7\%$ (6/7). A curative resection could be performed in three of the recurrent patients (2 locoregional and 1 distant recurrence). Conclusion: Our results suggest that FDG-PET may be useful for detecting locoregional and distant recurrence of gastric cancer and for selecting appropriate treatment. However, considering that FDG-PET was limited in detecting peritoneal seeding and determining the exact anatomical extension of tumor, it should be used in conjunction with other anatomical images.

• Investigative Magnetic Resonance Imaging
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• v.7 no.1
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• pp.12-21
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• 2003

Purpose : In order to overcome limitations in the existing conventional spectrometer, a new spectrometer with advanced functionalities is designed and implemented. Materials and Methods : We designed a spectrometer using the TMS320C6701 DSP capable of 1 giga floating point operations per second (GFLOPS). The spectrometer can generate continuously varying complicate gradient waveforms by real-time calculation, and select image plane interactively. The designed spectrometer is composed of two parts: one is DSP-based digital control part, and the other is analog part generating gradient and RF waveforms, and performing demodulation of the received RF signal. Each recover board can measure 4 channel FID signals simultaneously for parallel imaging, and provides fast reconstruction using the high speed DSP. Results : The developed spectrometer was installed on a 1.5 Tesla whole body MRI system, and performance was tested by various methods. The accurate phase control required in digital modulation and demodulation was tested, and multi-channel acquisition was examined with phase-array coil imaging. Superior image quality is obtained by the developed spectrometer compared to existing commercial spectrometer especially in the fast spin echo images. Conclusion : Interactive control of the selection planes and real-time generation of gradient waveforms are important functions required for advanced imaging such as spiral scan cardiac imaging. Multi-channel acquisition is also highly demanding for parallel imaging. In this paper a spectrometer having such functionalities is designed and developed using the TMS320C6701 DSP having 1 GFLOPS computational power. Accurate phase control was achieved by the digital modulation and demodulation techniques. Superior image qualities are obtained by the developed spectrometer for various imaging techniques including FSE, GE, and angiography compared to those obtained by the existing commercial spectrometer.