• Progress in Medical Physics
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• v.33 no.4
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• pp.37-52
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• 2022

Over the past decades, radiation therapy combined with imaging modalities that ensure optimal image guidance has revolutionized cancer treatment. The two major purposes of using imaging modalities in radiotherapy are to clearly delineate the target prior to treatment and set up the patient during radiation delivery. Image guidance secures target position prior to and during the treatment. High quality images provide an accurate definition of the treatment target and the possibility to reduce the treatment margin of the target volume, further lowering radiation toxicity and improving the quality of life of cancer patients. In this review, the various types of image guidance modalities used in radiation therapy are distinguished into ionized (kilovoltage and megavoltage image) and nonionized imaging (magnetic resonance image, ultrasound, surface imaging, and radiofrequency). The functional aspects, advantages, and limitation of imaging using these modalities are described as a subsection of each category. This review only focuses on the technological viewpoint of these modalities and any clinical aspects are omitted. Image guidance is essential, and its importance is rapidly increasing in modern radiotherapy. The most important aspect of using image guidance in clinical settings is to monitor the performance of image quality, which must be checked during the periodic quality assurance process.

• Journal of Distribution Science
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• v.11 no.4
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• pp.61-72
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• 2013

Purpose - It is widely accepted that the process of developing marketing strategy is composed of three steps: market segmentation, target market selection and positioning. However, mass marketing strategy based on cost reduction through economies of scale and standardized products, can be also an effective strategic option. Many marketing scholars including Theodore Levitt emphasize the importance of applying the mass production concept to various industries including service industries. Especially, in times of economic downturn, the capability of providing consumers with low-priced, value products can be an important source of competitive advantage, as well as the ability of providing high-priced premium products. Marketers should decide whether they will implement mass marketing strategy or target marketing strategy. The present study theoretically shows that firms should understand the target customers' price elasticity as well as the firm's cost structure in order to make such a strategic decision. Research design, data, and methodology - Instead of implementing an empirical study, this study provides a theoretical(mathematical) investigation on the effect of consumers' price elasticity on a firm's optimal price level, profit, sales volume, revenue, and cost. The results are mostly deduced from derivative calculations and several graphs are utilized to represent the results on the relationships between the variables under study. Results - The analytical results suggest that it is more profitable for a firm to adopt the segment/target marketing strategy (more specifically the differentiation strategy) when the degree of consumers' heterogeneity is high and the proportion of the fixed cost in the total cost is low. On the other hand, if the degree of consumers' heterogeneity is low and the fixed cost is high, it is better to adopt the mass marketing strategy or the cost leadership strategy. The strategy of concentrating on a single target market will be effective when consumers' needs are highly heterogeneous but the fixed cost is high. Any of the three types of generic strategies proposed my Porter(1980, 1985) can be applied when both the consumers' heterogeneity and the fixed cost are low. This study also proposes the contribution-margin-based method for developing the optimal pricing strategy. Conclusions - One of the primary roles of marketers is to find a proper compromise between the two conflicting goals of maximizing customer satisfaction and minimizing cost. In order to do so, he or she should understand the characteristics of the target customers as well as the cost structure of the firm. In addition to the theoretical analyses, this study discusses several business cases and explains how superior companies find the optimal compromise position between these two goals and dominate the market. One of the radical changes recently taking place in business arena is the reduction of production and distribution costs of both physical goods and information due to the advancement and the wide diffusion of information technology. The cost reduction combined with lowered priced elasticity incurred by customized products and services, will enable many firms to adopt the mass customization strategy.

• The Journal of Engineering Geology
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• v.32 no.2
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• pp.221-239
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• 2022

Unknown geotechnical characteristics are key challenges in the design of piles for the plant, civil and building works. Although the N-values which were read through the standard penetration test are important, those N-values of the whole area are not likely acquired in common practice. In this study, the N-value is predicted by means of regression analysis with artificial intelligence (AI). Big data is important to improve learning performance of AI, so circular augmentation method is applied to build up the big data at the current study. The optimal model was chosen among applied AI algorithms, such as artificial neural network, decision tree and auto machine learning. To select optimal model among the above three AI algorithms is to minimize the margin of error. To evaluate the method, actual data and predicted data of six performed projects in Poland, Indonesia and Malaysia were compared. As a result of this study, the AI prediction of this method is proven to be reliable. Therefore, it is realized that the geotechnical characteristics of non-boring points were predictable and the optimal arrangement of structure could be achieved utilizing three dimensional N-value distribution map.

• Radiation Oncology Journal
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• v.18 no.2
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• pp.107-113
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• 2000

Purpose : The goal of this study 닌as to improve the accuracy of three-dimensional conformal radiotherapy (3-D CRT) by measuring the treatment setup error and physiological movement of liver based on the analysis of images which were obtained by electronic portal imaging device (EPID). Materials and Methods : For 10 patients with hepatocellular carcinoma, 4-7 portal images were obtained by using EPID during the radiotherapy from each patient daiiy. We analyzed the setup error and physiological movement of liver based on the verification data. We also determined the safety margin of the tumor in 3-D CRT through the analysis of physiological movement. Results : The setup errors were measured as 3mm with standard deviation 1.70 mm in x direction and 3.7 mm with standard deviation 1.88 mm in y direction respectively. Hence, deviation were smaller than 5mm from the center of each axis. The measured range of liver movement due to the physiological motion was 8.63 mm on the average. Considering the motion of liver and setup error, the safety margin of tumor was at least 15 mm. Conclusion : EPID is a very useful device for the determination of the optimal margin of the tumor, and thus enhance the accuracy and stability of the 3-D CRT in patients with hepatocellular carcinoma.

• Radiation Oncology Journal
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• v.23 no.4
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• pp.236-242
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• 2005

Purpose: To evaluate the role of surgical clips and scars in determining electron boost field for early stage breast cancer undergoing conserving surgery and postoperative radiotherapy and to provide an optimal method in drawing the boost field. Materials and Methods: Twenty patients who had $4{\sim}7$ surgical clips in the excision cavity were selected for this study. The depth informations were obtained to determine electron energy by measuring the distance from the skin to chest wall (SCD) and to the clip implanted in the most posterior area of tumor bed. Three different electron fields were outlined on a simulation film. The radiological tumor bed was determined by connecting all the clips implanted during surgery Clinical field (CF) was drawn by adding 3 cm margin around surgical scar. Surgical field (SF) was drawn by adding 2 cm margin around surgical clips and an Ideal field (IF) was outlined by adding 2 cm margin around both scar and clips. These fields were digitized into our planning system to measure the area of each separate field. The areas of the three different electron boost fields were compared. Finally, surgical clips were contoured on axial CT images and dose volume histogram was plotted to investigate 3-dimensional coverage of the clips. Results : The average depth difference between SCD and the maximal clip location was $0.7{\pm}0.55cm$. Greater difference of 5 mm or more was seen in 12 patients. The average shift between the borders of scar and clips were 1.7 1.2, 1.2, and 0.9 cm in superior, inferior, medial, and lateral directions, respectively. The area of the CF was larger than SF and IF in 6y20 patients. In 15/20 patients, the area difference between SF and if was less than 5%. One to three clips were seen outside the CF in 15/20 patients. In addition, dosimetrically inadequate coverage of clips (less than 80% of prescribed dose) were observed in 17/20 patients when CF was used as the boost field. Conclusion: The electron field determined from clinical scar underestimates the tumor bed in superior-inferior direction significantly and thereby underdosing the tissue at risk. The electron field obtained from surgical clips alone dose not cover the entire scar properly As a consequence, our technique, which combines the surgical clips and clinical scars in determining electron boost field, was proved to be effective in minimizing the geographical miss as well as normal tissue complications.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.5
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• pp.1925-1928
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• 2015

Background: To investigate whether CT findings can predict the invasiveness of persistent cancerous pure ground glass opacity (pGGO) by correlating the CT imaging features of persistent pGGO with pathological changes. Materials and Methods: Ninety five patients with persistent pGGOs were included. Three radiologists evaluated the morphologic features of these pGGOs at high resolution CT (HRCT). Binary logistic regression was used to assess the association between CT findings and histopathological classification (pre-invasive and invasive groups). Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of diameters. Results: A total of 105 pGGOs were identified. Between pre-invasive (atypical adenomatous hyperplasia, AAH, and adenocarcinoma in situ, AIS) and invasive group (minimally invasive adenocarcinoma, MIA and invasive lung adenocarcinomas, ILA), there were significant differences in diameter, spiculation and vessel dilatation (p<0.05). No difference was found in air-bronchogram, bubble-lucency, lobulated-margin, pleural indentation or vascular convergence (p>0.05). The optimal threshold value of the diameters to predict the invasiveness of pGGO was 12.50mm. Conclusions: HRCT features can predict the invasiveness of persistent pGGO. The pGGO with a diameter more than 12.50mm, presences of spiculation and vessel dilatation are important factors to differentiate invasive adenocarcinoma from pre-invasive cancerous lesions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.11
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• pp.47-53
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• 2006

The power losses due to modulation index for multi-modulation scheme were analyzed under various transmission mode of satellite control and the necessary satellite link margin for transmission mode were proposed in this paper On the basis of the analyses for interference between the transmission signals and threshold of satellite control signal receiver, the optimal subcarrier signals were proposed for satellite range measurement methods, respectively. The subcarrier signal of 12 kHz or 14 kHz is proper for telecommand using the ESA method, and 16 kHz for telecommand signal using the GSTDN method. On the other hand, the telemetry subcarrier of 65.536 kHz is a proper in the viewpoint of receiver threshold value.

• Clinics in Shoulder and Elbow
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• v.20 no.4
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• pp.230-235
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• 2017

Background: Neer type II distal clavicle fractures have the drawback of coracoclavicular instability and insufficient distal bony fragment, thereby making it difficult to achieve adequate fixation. Although various surgical treatments have been described for Neer type II fracture, the optimal treatment remains controversial. This study reports the clinical results and usefulness of anatomical locking plate with additional K-wire fixation. Methods: A totally of 21 patients with type II distal clavicle fracture were included in the study. The surgical procedure reduced the fracture temporarily; it included insertion of one or two K-wire from the lateral margin of the distal fragment to the proximal fragment through the fracture site, followed by application and fixation of the locking plate. The bony union and migration of K-wire was evaluated in the follow-up radiography. The coracoclavicular distance and acromioclavicular joint arthrosis were assessed at the final follow-up. The Constant Score (CS) and Korean Shoulder Score (KSS) were evaluated for clinical scoring. Results: Bone union was achieved in all cases. At the final follow-up, coracoclavicular distance of the injured shoulder was increased, as compared to the intact shoulder (p=0.002), with no accompanying clinical symptoms. No K-wire migration was observed. At the final follow-up, K-wire irritation was observed in two cases and acromioclavicular arthrosis in one case, with no other adverse effects. Pain visual analogue scale, CS, and KSS were improved in all cases. Conclusions: The method of anatomical locking plate with additional K-wire fixation could be useful in achieving beneficial clinical results.

• The Korean Journal of Pain
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• v.13 no.2
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• pp.182-186
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• 2000

Background: Ropivacaine is a new amide local anesthetics, having therapeutic properties similar to those of bupivacaine but less cardiovascular toxicity and motor blockade. The aim of this study was to evaluate the effects of ropivacaine used in stellate ganglion block (SGB) compared with those of lidocaine or bupivacaine. Methods: This prospective and crossover study performed in twenty patients with sudden sensory neural hearing loss. All patients received three times SGB, in the paratracheal approach using 8 ml of 1% lidocaine, 0.2% bupivacaine, and 0.2% ropivacaine respectively without any orders. Onset time and action duration of Horner's syndrome were observed after each SGB. Results: Onset time of ropivacaine was the middle of the three agents; earlier lidocaine and slower bupivacaine. Lidocaine ($3.0{\pm}1.9$ min), bupivacaine ($4.1{\pm}2.9$ min) and ropivacaine ($3.3{\pm}1.3$ min). But there were no significant differences; Action duration of Horner's syndrome of ropivacaine (223.6?105.2 min) was longer than lidocaine ($134.6{\pm}77.3$ min) and shorter than bupivacaine ($241.2{\pm}115.8$ min). There were significant differences in the action duration of each local anesthetics (P<0.05). There was no critical side effects and temporary foreign body sensation was the most common side effect. Conclusions: We conclude that ropivacaine is a good alternative in SGB instead of lidocaine or bupivacaine. Ropivacaine is a long acting local anesthetic similar to those of bupivacaine with wide margin of safety. However, optimal concentration and volume of ropivacaine in SGB should be studied.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1950-1957
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• 2015

Modern wind generators (WGs) are forced or encouraged to participate in frequency control in the form of inertial and/or primary control to improve the frequency stability of power systems. To participate in primary control, WGs should perform deloaded operation that maintains reserve power using speed and/or pitch-angle control. This paper proposes an optimization formulation that allocates the required reserve to WGs to maximize the kinetic energy (KE) stored in a wind power plant (WPP). The proposed optimization formulation considers the rotor speed margin of each WG to the maximum speed limit, which is different from each other because of the wake effects in a WPP. As a result, the proposed formulation allows a WG with a lower rotor speed to retain more KE in the WPP. The performance of the proposed formulation was investigated in a 100-MW WPP consisting of 20 units of 5-MW permanent magnet synchronous generators using an EMTP-RV simulator. The results show that the proposed formulation retains the maximum amount of KE with the same reserve and successfully increases the frequency nadir in a power system by releasing the stored KE in a WPP in the case of a disturbance.