• Journal of Korean Neurosurgical Society
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• 제67권1호
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• pp.60-72
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• 2024

Objective : Recently, robotic-assisted spine surgery (RASS) has been considered a minimally invasive and relatively accurate method. In total, 495 robotic-assisted pedicle screw fixation (RAPSF) procedures were attempted on 100 patients during a 14-month period. The current study aimed to analyze the accuracy, potential risk factors, and learning curve of RAPSF. Methods : This retrospective study evaluated the position of RAPSF using the Gertzbein and Robbins scale (GRS). The accuracy was analyzed using the ratio of the clinically acceptable group (GRS grades A and B), the dissatisfying group (GRS grades C, D, and E), and the Surgical Evaluation Assistant program. The RAPSF was divided into the no-breached group (GRS grade A) and breached group (GRS grades B, C, D, and E), and the potential risk factors of RAPSF were evaluated. The learning curve was analyzed by changes in robot-used time per screw and the occurrence tendency of breached and failed screws according to case accumulation. Results : The clinically acceptable group in RAPSF was 98.12%. In the analysis using the Surgical Evaluation Assistant program, the tip offset was 2.37±1.89 mm, the tail offset was 3.09±1.90 mm, and the angular offset was 3.72°±2.72°. In the analysis of potential risk factors, the difference in screw fixation level (p=0.009) and segmental distance between the tracker and the instrumented level (p=0.001) between the no-breached and breached group were statistically significant, but not for the other factors. The mean difference between the no-breach and breach groups was statistically significant in terms of pedicle width (p<0.001) and tail offset (p=0.042). In the learning curve analysis, the occurrence of breached and failed screws and the robot-used time per screw screws showed a significant decreasing trend. Conclusion : In the current study, RAPSF was highly accurate and the specific potential risk factors were not identified. However, pedicle width was presumed to be related to breached screw. Meanwhile, the robot-used time per screw and the incidence of breached and failed screws decreased with the learning curve.

• Journal of Radiation Protection and Research
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• 제48권1호
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• pp.20-27
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• 2023

Background: As the number of nuclear facilities nearing their pre-determined design life increases, demand is increasing for technology and infrastructure related to the decommissioning and decontamination (D&D) process. It is necessary to consider the nature of the dismantling environment constantly changing and the worker doing new tasks. A method was studied that can calculate the effect of learning and the change in work time on the work process, according to the learning-forgetting curve model (LFCM). Materials and Methods: The LFCM was analyzed, and input values and scenarios were analyzed for substitution into the D&D process of a nuclear facility. Results and Discussion: The effectiveness and efficiency of the training were analyzed. It was calculated that skilled workers can receive a 16.9% less collective radiation dose than workers with only basic training. Conclusion: Using these research methods and models, it was possible to calculate the change in the efficiency of workers performing new tasks in the D&D process and the corresponding reduction in the work time and collective dose.

• 한국디자인학회:학술대회논문집
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• 한국디자인학회 2004년도 추계 학술발표대회 논문집
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• pp.142-143
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• 2004

• 한국수학교육학회지시리즈A:수학교육
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• 제38권1호
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• pp.87-94
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• 1999

A multimedia CD title is developed for learning simple closed curve and Mobius band which are one of mathematics contents in the first grade of middle school. This title visualizes various figures through graphics and animations so that students can easily understand the relevant concepts and learn them with fun. It is shown that 88.6% of 30 sampled teachers are positive for the title and that 86.7% want to use it as a teaching tool in their classes.

• 한국경영과학회지
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• 제30권3호
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• pp.137-149
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• 2005

This study proposes a framework enhancing the accuracy of estimation for project duration by combining linear Bayesian updating scheme with the learning curve effect. Activities in a particular project might share resources in various forms and might be affected by risk factors such as weather Statistical dependence stemming from such resource or risk sharing might help us learn about the duration of upcoming activities in the Bayesian model. We illustrate, using a Monte Carlo simulation, that for partially repetitive projects a higher degree of statistical dependence among activity duration results in more variation in estimating the project duration in total, although more accurate forecasting Is achievable for the duration of an individual activity.

• Journal of Gastric Cancer
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• 제12권3호
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• pp.156-163
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• 2012

Purpose: Laparoscopic gastrectomy is a widely accepted surgical technique. Recently, robotic gastrectomy has been developed, as an alternative minimally invasive surgical technique. This study aimed to evaluate the question of whether robotic gastrectomy is feasible and safe for the treatment of gastric cancer, due to its learning curve. Materials and Methods: We retrospectively reviewed the prospectively collected data of 100 consecutive robotic gastrectomy patients, from November 2008 to March 2011, and compared them to 282 conventional laparoscopy patients during the same period. The robotic gastrectomy patients were divided into 20 initial cases; and all subsequent cases; and we compared the clinicopathological features, operating times, and surgical outcomes between the three groups. Results: The initial 20 robotic gastrectomy cases were defined as the initial group, due to the learning curve. The initial group had a longer average operating time ($242.25{\pm}74.54$ minutes vs. $192.56{\pm}39.56$ minutes, P>0.001), and hospital stay ($14.40{\pm}24.93$ days vs. $8.66{\pm}5.39$ days, P=0.001) than the experienced group. The length of hospital stay was no different between the experienced group, and the laproscopic gastrectomy group ($8.66{\pm}5.39$ days vs. $8.11{\pm}4.10$ days, P=0.001). The average blood loss was significantly less for the robotic gastrectomy groups, than for the laparoscopic gastrectomy group ($93.25{\pm}84.59$ ml vs. $173.45{\pm}145.19$ ml, P<0.001), but the complication rates were no different. Conclusions: Our study shows that robotic gastrectomy is a safe and feasible procedure, especially after the 20 initial cases, and provides a satisfactory postoperative outcome.

• Journal of Korean Neurosurgical Society
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• 제40권1호
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• pp.16-21
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• 2006

Objective : Young neurosurgeons need to focus on the mortality and morbidity of aneurysmal neck clipping to develop a personal experience with an initial series. Methods : Total 88 aneurysms from 75 patients who underwent neck clipping by the same operator from 2001 to 2004 were reviewed. Patients were divided into three groups : first year [Group I], second year [Group II], and third year [Group III] in each group. Location of aneurysm, age, Fisher grade, Hunter-Hess grade [H-H grade], postoperative Glasgow outcome scale [GOS], and complications related to surgical procedures were evaluated with Chi-square and logistic regression analyses. Results : Fourteen patients had complications related to surgery [18.7%]. The major causes of mortality and morbidity related to surgery were cerebral infarction, hemorrhage and brain swelling due to intraoperative rupture, brain retraction and vasospasm. Among the 4 cases of mortality were 2 patients in Group I, 1 patient in Group II and 1 patient in Group III, and location of aneurysms were 2 internal carotid artery[ICA] and 2 posterior communicating artery[PCoA] aneurysms. There were 4 morbidity and new neurological deficits in Group I, 4 in Group II and 2 in Group III. Although mortality and morbidity during the learning curve had a statistical significance in H-H grade, age [>60 years old], and aneurysm location [especially ICA aneurysm] as variables, mortality mainly occurred in ICA and PCoA aneurysms. Conclusion : Experienced supervision or endovascular approach should be considered for the treatment of ICA and PCoA aneurysms during the learning curve.

• Journal of Korean Neurosurgical Society
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• 제58권6호
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• pp.539-546
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• 2015

Objective : To report the learning curve of percutaneous endoscopic lumbar discectomy (PELD) for a surgeon who had not been previously exposed to this procedure based on the period and detailed technique with a retrospective matched comparative design. Methods : Of 213 patients with lumbar disc herniation encountered during the reference period, 35 patients who were followed up for 1 year after PELD were enrolled in this study. The patients were categorized by the period and technique of operation : group A, the first 15 cases, who underwent by the 'in-and-out' technique; group B, the next 20 cases, who underwent by the 'in-and-out-and-in' technique. The operation time, failure rate, blood loss, complication rate, re-herniation rate, the Visual Analogue Scale (VAS) for back and leg were checked. The alteration of dural sac cross-sectional area (DSCSA) between the preoperative and the postoperative MRI was checked. Results : Operative time was rapidly reduced in the early phase, and then tapered to a steady state for the 35 cases receiving the PELD. After surgery, VAS scores for the back and leg were decreased significantly in both groups. Complications occurred in 2 patients in group A and 2 patients in group B. Between the two groups, there were significant differences in operative time, improvement of leg VAS, and expansion of DSCSA. Conclusion : PELD learning curve seems to be acceptable with sufficient preparation. However, because of their high tendency to delayed operation time, operation failure, and re-herniation, caution should be exercised at the early phase of the procedure.

• International journal of thyroidology
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• 제11권2호
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• pp.130-136
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• 2018

Background and Objectives: Intraoperative neural monitoring (IONM) of recurrent laryngeal nerve (RLN) in thyroid surgery has been employed worldwide to identify and preserve the nerve as an adjunct to visual identification. The aims of this study was to evaluate the efficacy of IONM and difficulties in the learning curve. Materials and Methods: We studied 63 patients who underwent thyroidectomy with IONM during last 2 years. The standard IONM procedure was performed using NIM 3.0 or C2 Nerve Monitoring System. Patients were divided into two chronological groups based on the success rate of IONM (33 cases in the early period and 30 cases in the late period), and the outcomes were compared between the two groups. Results: Of 63 patients, 32 underwent total thyroidectomy and 31 thyroid lobectomy. Failure of IONM occurred in 9 cases: 8 cases in the early period and 1 case in the late period. Loss of signal occurred in 8 nerves of 82 nerves at risk. The positive predictive value increased from 16.7% in the early period to 50% in the late period. The mean amplitude of the late period was higher than that of the early period (p<0.001). Conclusion: IONM in thyroid surgery is effective to preserve the RLN and to predict postoperative nerve function. However, failure of IONM and high false positive rate can occur in the learning curve, and the learning curve was about 30 cases based on the results of this study.

• 대한영상의학회지
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• 제81권5호
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• pp.1164-1174
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• 2020

목적 수술 전 초음파 검사에서 갑상선 종양의 재발을 예측할 수 있는 심층 학습 모델을 개발하고자 한다. 대상과 방법 수술 전 초음파에서 병리학적으로 확진된 갑상선 수술을 받은 229명의 환자(남성:여성 = 42:187, 평균 연령, 49.6세)의 대표적인 초음파 이미지를 포함시켰다. 각각 대표적인 횡축 또는 종축 초음파 이미지가 선택되었다. 신경 네트워크용 Python 2.7.6 및 Keras 2.1.5, convolutional neural network을 사용한 심층 학습이 사용되었다. 재발한 환자와 재발이 없는 환자의 임상 및 조직학적 특징을 비교하였다. 그룹 간의 심층 학습 모델의 receiver operating characteristic curve 곡선 아래의 영역은 재발 갑상선암을 예측하기 위한 심층 학습 모델의 예측에 사용되었다. 결과 전체 환자 229명 중 49명이 종양 재발(21.4%)을 보였다. 종양의 크기, 다원성은 재발이 없는 군과 재발 군에서 유의한 차이가 있었다(p < 0.05). 재발성 갑상선암 예측을 위한 심층 학습 모델의 전반적인 평균 area under the curve (이하 AUC) 값은 0.9 ± 0.06이었다. 평균 AUC는 macrocarcinoma에서 0.87 ± 0.03, microcarcinoma에서 0.79 ± 0.16이었다. 결론 갑상선암의 초음파 이미지를 이용한 심층 학습 모델로 갑상선암 재발의 예측 모델 구축의 가능성을 보여주었다.