• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.10
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• pp.84-91
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• 2016

Most recently, the technology of around view monitoring(AVM) system or the security systems could provide users with images by using a fisheye lens. The filmed images through fisheye lens have an advantage of providing a wider range of scenes. On the other hand, filming through fisheye lens also has disadvantages of distorting images. Especially, it causes the sharpness of images to degrade because the edge of images is out of focus. The influence of a blur still remains at the end of the range when the super-resolution techniques is applied in order to enhance the sharpness. It degrades the clarity of high resolution images and occurs artifacts, which leads to deterioration in the performance of super-resolution algorithm. Therefore, in this paper we propose self-similarity-based pre-processing method to improve the sharpness at the edge. Additionally, we implement the acceleration in the GPU environment of entire algorithm and verify the acceleration.

• Journal of Korean Neurosurgical Society
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• v.46 no.4
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• pp.378-384
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• 2009

Objective : In order to establish the role of Gamma Knife radiosurgery (GKS) in large intracranial arteriovenous malformations (AVMs), we analyzed clinical characteristics, radiological features, and radiosurgical outcomes. Methods : Between March 1992 and March 2005, 28 of 33 patients with large AVMs (> $10\;cm^3$ in nidus-volume) who were treated with GKS underwent single session radiosurgery (RS), and the other 5 patients underwent staged volumetric RS. Retrospectively collected data were available in 23 cases. We analyzed treatment outcomes in each subdivided groups and according to the AVM sizes. We compared the estimated volume, defined as primarily estimated nidus volume using MR images, with real target volume after excluding draining veins and feeding arteries embedded into the nidus. Results : Regarding those patients who underwent single session RS, 44.4% (8/18) had complete obliteration; regarding staged volumetric RS, the obliteration rate was 40% (2/5). The complete obliteration rate was 60% (6/10) in the smaller nidus group ($10-15\;cm^3$ size), and 25% (2/8) in the larger nidus group (over $15\;cm^3$ size). One case of cerebral edema and two cases (8.7%) of hemorrhage were seen during the latent period. The mean real target volume for 18 single sessions of RS was $17.1\;cm^3$ ($10.1-38.4\;cm^3$), in contrast with the mean estimated volume of $20.9\;cm^3$ ($12.0-45.0\;cm^3$). Conclusion : The radiosurgical treatment outcomes of large AVMs are generally poor. However, we presume that the recent development in planning software and imaging devices aid more accurate measurement of the nidus volume, therefore improving the treatment outcome.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.37-43
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• 2010

In this paper, a reliability-based design optimization is developed for the topology design of linear structures using a performance measure approach. Spatial domain is discretized using three dimensional Reissner-Mindlin plate elements and design variable is taken as the material property of each element. A continuum based adjoint variable method is employed for the efficient computation of sensitivity with respect to the design and random variables. The performance measure approach of RBDO is employed to evaluate the probabilistic constraints. The topology optimizationproblem is formulated to have probabilistic displacement constraints. The uncertainties such as material property and external loads are considered. Numerical examples show that the developed topology optimization method could effectively yield a reliable design, comparing with the other methods such as deterministic, safety factor, and worst case approaches.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.1
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• pp.27-33
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• 2007

Purpose: We have performed SRS (stereotactic radiosurgery) for avm (arterry vein malformation) and brain cancer. In order to verify dose and localization of SRS, dose distributions from TPS ($X-Knife^{(R)}$ 3.0, Radionics, USA) and GafChromic $EBT^{(R)}$ film in a head phantom were compared. Materials and Methods: In this study, head and neck region of conventional humanoid phantom was modified by substituting one of 2.5 cm slap with five 0.5 cm acrylic plates to stack the GafChromic $EBT^{(R)}$ film slice by slice with 5 mm intervals. Four films and five acrylic plates were cut along the contour of head phantom in axial plane. The head phantom was fixed with SRS head ring and adapted SRS localizer as same as real SRS procedure. CT images of the head phantom were acquired in 5 mm slice intervals as film interval. Five arc 6 MV photon beams using the SRS cone with 2 cm diameter were delivered 300 cGy to the target in the phantom. Ten small pieces of the film were exposed to 0, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900 cGy, respectively to calibrate the GafChromic $EBT^{(R)}$ film. The films in the phantom were digitized after 24 hours and its linearity was calibrated. The pixel values of the film were converted to the dose and compared with the dose distribution from the TPS calculation. Results: Calibration curve for the GafChromic $EBT^{(R)}$ film was linear up to 900 cGy. The R2 value was better than 0.992. Discrepancy between calculated from $X-Knife^{(R)}$ 3.0 and measured dose distributions with the film was less than 5% through all slices. Conclusion: It was possible to evaluate every slice of humanoid phantom by stacking the GafChromic EBT film which is suitable for 2 dimensional dosimetry, It was found that film dosimetry using the GafChromic $EBT^{(R)}$ film is feasible for routine dosimetric QA of stereotactic radiosurgery.

• Radiation Oncology Journal
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• v.15 no.3
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• pp.215-224
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• 1997

Purpose : Stereotactic radiosurgery with external beam irradiation successfully obliterates carefully selected intracranial arteriovenous malformation (AVM) . We Present clinical and radiological long term results after treatment with a single high dose irradiation using a linear accelerator. Materials and Methods : Rrom January 1991 to June 1994, fifteen patients with intracranial AVM were treated in our hospital with the stereotactic radiosurgery using a linear accelerator. The radiation was delivered using a 6 MV linear accelerator. The prescribed doses at the isocenter varied from 1800 to 2500cGy (median : 2000cGy) and were given as a sin91e fraction. The radiation doses at the periphery of the lesion typically corresponded to the 80-90% isodose line. In 14 patients, complete clinical and/or radiological follow-up examination were available. Results : Angiography was available in 13 patients with a follow-up Period from 18 months to 27 months. Of 13 patients, the overall complete obliteration rate was 92.3% (12 patients). This incidence did not correlate with lesion size. Seizure, headache and progressive neurologic deficit were complete recovered. One Patient experienced hemorrhage at 2 months after treatment. One patient developed radiation induced brain edema in the white matter surrounding nidus at 16 months after treatment and showed complete resolution of the edema in MR image obtained at 27 months after treatment. After a follow-up period of up to 6 years, no radiation induced severe late complications occurred. Conclusion : We conclude that stereotactic radiosurgery using a linear accelerator is an effective and safe therapy for symptomatic and surgically inaccessible intracranial AVMs and the results compare favorably to the more expensive and elaborate systems that are currently available for stereotactic radiosurgery.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.1
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• pp.9-18
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• 2015

In this paper, we verify the optimal topology design for heat conduction problems in steady stated which is obtained numerically using the adjoint design sensitivity analysis(DSA) method. In adjoint variable method(AVM), the already factorized system matrix is utilized to obtain the adjoint solution so that its computation cost is trivial for the sensitivity. For the topology optimization, the design variables are parameterized into normalized bulk material densities. The objective function and constraint are the thermal compliance of the structure and the allowable volume, respectively. For the experimental validation of the optimal topology design, we compare the results with those that have identical volume but designed intuitively using a thermal imaging camera. To manufacture the optimal design, we apply a simple numerical method to convert it into point cloud data and perform CAD modeling using commercial reverse engineering software. Based on the CAD model, we manufacture the optimal topology design by CNC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4704-4710
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• 2015

The purpose of this study is to obtain a useful diagnostic image by increasing the signal strength of the peripheral artery, was to use a T1 shortening effect of gadolinium contrast agents to improve the disadvantages of the phase image. From october to december 2014 thirty patients were underwent the MRI scanning, except for heart disease. Research method was evaluated comparing the image after gadolinium contrast MR image acquisition step before evaluating the difference between the signal intensity for T1 shortening effect. In frontal lobe 19.45%, temporal lobe 23.09%, occipital lobe 25.45%, parietal lobe 18.82%, cerebellum 20.93% after peripheral arterial signal strength results of gadolinium contrast agent injection was increased significantly after injection of gadolinium both statistically significant. After injecting a contrast agent gadolinium in SWI by increasing the signal strength of the T1 shortening effect can be obtained when using the phase image to give a useful image in diagnosis and treatment.

• Progress in Medical Physics
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• v.21 no.3
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• pp.274-280
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• 2010

The purpose of this study was to analyze the effect of single-fraction stereotactic radiosurgery (SRS) for the treatment of 15 cases of cerebral arteriovenous malformations (AVMs). Between 2002 and 2009, of the 25 patients who had SRS for the treatment of cerebral AVM, 15 patients (6 men, 9 women) taken a digital subtraction angiography (DSA) over 12 months after SRS were included. We retrospectively evaluated the size, location, hemorrhage of nidus, angiographic changes on follow-up on the MR angiography and DSA, and clinical complications during follow-up periods. At a median follow-up of 24 months (range 12-89), complete obliteration of nidus was observed in all patients (100%) while residual draining veins was observed in 3 patients (20%). There was no clinical complication during the follow-up period except seizure in 1 patient. The mean nidus volume was 4.7cc (0.5~11.7 cc, SD 3.7 cc). The locations of nidus were in cerebral hemisphere in 11 patients, cerebellum in 2 patients, basal ganglia in 1 patient, and pons in 1 patient respectively. 9 cases were hemorrhagic, and 6 cases were non-hemorrhagic AVMs. The SRS with LINAC is a safe and effective treatment for cerebral AVMs when the follow up period is over 4 years. However, it is recommended to continue to follow up until the draining vein on arterial phase of follow up DSA disappears completely.

• Journal of Korean Neurosurgical Society
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• v.64 no.6
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• pp.882-890
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• 2021

Objective : The aim of this study to investigate the benefits of patient-based 3-dimensional (3D) cerebral arteriovenous malformation (AVM) models for preoperative surgical planning and education. Methods : Fifteen patients were operated on for AVMs between 2015 and 2019 with patient-based 3D models. Ten patients' preoperative cranial angiogram screenings were evaluated preoperatively or perioperatively via patient-based 3D models. Two patients needed emergent surgical intervention; their models were solely designed based on their AVMs and used during the operation. However, the other patients who underwent elective surgery had the modeling starting from the skull base. These models were used both preoperatively and perioperatively. The benefits of patients arising from treatment with these models were evaluated via patient files and radiological data. Results : Fifteen patients (10 males and five females) between 16 and 66 years underwent surgery. The mean age of the patients was 40.0±14.72. The most frequent symptom patients observed were headaches. Four patients had intracranial bleeding; the symptom of admission was a loss of consciousness. Two patients (13.3%) belonged to Spetzler-Martin (SM) grade I, four (26.7%) belonged to SM grade II, eight (53.3%) belonged to SM grade III, and one (6.7%) belonged to SM grade IV. The mean operation duration was 3.44±0.47 hours. Three patients (20%) developed transient neurologic deficits postoperatively, whereas three other patients died (20%). Conclusion : Several technological innovations have emerged in recent years to reduce undesired outcomes and support the surgical team. For example, 3D models have been employed in various surgical procedures in the last decade. The routine usage of patient-based 3D models will not only support better surgical planning and practice, but it will also be useful in educating assistants and explaining the situation to the patient as well.

• Radiation Oncology Journal
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• v.9 no.1
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• pp.53-58
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• 1991

From February 1987 through July 1990, the seventeen cases of inoperable intracranial arteriovenous malformation (AVM) were treated using 6 MV linear accelerator at the Division of Therapautic Radiology, Kang Nam 51. Mary's Hospital. Of seventeen cases, fourteen were male and three were female. Ages ranged from 10 to 51 years (median age of 25 years). The main symtoms were headache, epilepsy and hemiparesis in decreasing order of frequency. The middle cerebral artery is the most common origin of the feeding vessel $(41.2\%)$. Four were treated by conventionally fractionated radiation therapy (CRT, thirteen were treated by stereotactic radiosurgery (RS). duration or follow-up in CRT and RS group were 4 to 43 months (median 33 months) and 3 to 12 months (median 13 months), respectively. When the response was assessed by radiologic follow-up study, two of four CRT group showed minimal response. Of thirteen cases of RS group, two $(15.4\%)$ showed complete response, five $(38\%)$ partial response, two $(15.4\%)$ minimal response and four $(30.7\%)$ no response by the same assessment. There was no statistical significance in terms of follow-up period (p=0.22), size of lesion (p=0.82) and treated dose (p=0.05). Further accumulation of experience is recommended with proper case selection and sufficient follow-up period.