• Journal of radiological science and technology
• /
• v.45 no.6
• /
• pp.491-502
• /
• 2022

The purpose of this study was to retrospectively investigate the upper and lower control limits of treatment planning parameters using EBT film based delivery quality assurance (DQA) results and to analyze the results of statistical process control (SPC) in helical tomotherapy (HT). A total of 152 patients who passed or failed DQA results were retrospectively included in this study. Prostate (n = 66), rectal (n = 51), and large-field cancer patients, including lymph nodes (n = 35), were randomly selected. The absolute point dose difference (DD) and global gamma passing rate (GPR) were analyzed for all patients. Control charts were used to evaluate the upper and lower control limits (UCL and LCL) for all the assessed treatment planning parameters. Treatment planning parameters such as gantry period, leaf open time (LOT), pitch, field width, actual and planning modulation factor, treatment time, couch speed, and couch travel were analyzed to provide the optimal range using the DQA results. The classification and regression tree (CART) was used to predict the relative importance of variables in the DQA results from various treatment planning parameters. We confirmed that the proportion of patients with an LOT below 100 ms in the failure group was relatively higher than that in the passing group. SPC can detect QA failure prior to over dosimetric QA tolerance levels. The acceptable tolerance range of each planning parameter may assist in the prediction of DQA failures using the SPC tool in the future.

• Radiation Oncology Journal
• /
• v.30 no.2
• /
• pp.62-69
• /
• 2012

Purpose: To evaluate the treatment outcome and prognostic factor of postoperative radiotherapy for extremity soft tissue sarcoma (STS). Materials and Methods: Forty three patients with extremity STS were treated with conservative surgery and postoperative radiotherapy from January 1981 to December 2010 at Korea University Medical Center. Median total 60 Gy (range, 50 to 74.4 Gy) of radiation was delivered and 7 patients were treated with chemotherapy. Results: The median follow-up period was 70 months (range, 5 to 302 months). Twelve patients (27.9%) sustained relapse of their disease. Local recurrence occurred in 3 patients (7.0%) and distant metastases developed in 10 patients (23.3%). The 5-year overall survival (OS) was 69.2% and disease free survival was 67.9%. The 5-year local relapse-free survival was 90.7% and distant relapse-free survival was 73.3%. On univariate analysis, no significant prognostic factors were associated with development of local recurrence. Histologic grade (p = 0.005) and stage (p = 0.02) influenced the development of distant metastases. Histologic grade was unique significant prognostic factor for the OS on univariate and multivariate analysis. Severe acute treatment-related complications, Common Terminology Criteria for Adverse Events (CTCAE) grade 3 or 4, developed in 6 patients (14.0%) and severe late complications in 2 patients (4.7%). Conclusion: Conservative surgery with postoperative radiotherapy achieved a satisfactory rate of local control with acceptable complication rate in extremity STS. Most failures were distant metastases that correlate with tumor grade and stage. The majority of local recurrences developed within the field. Selective dose escalation of radiotherapy or development of effective systemic treatment might be considered.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.5
• /
• pp.2195-2199
• /
• 2014

Background: Despite being rare in incidence, malignant tumors of major salivary glands show diverse histological variation. There are limited data on major salivary gland tumor management and outcome from Pakistan. The objective of this study was to share our experience with management of malignant tumors of major salivary glands. Materials and Methods: Patients who received treatment at Shaukat Khanum Cancer Hospital and Research Center from July 2002 to June 2011 with an underlying diagnosis of a major salivary gland malignancy were included. Patient characteristics and treatment modalities were assessed. Local, regional and distant failures were determined. Disease free survival (DFS) and overall survival (OS) were calculated using Kaplan Meier curves and the Log rank test was used to determine statistical significance. Univariate and multivariate analyses were performed using Cox proportional hazard regression. Results: The parotid gland was the primary site of origin in 104 (80%) patients. Mucoepidermoid carcinoma (43%) and adenoid cystic carcinoma (24%) were the most common histological types. Surgery followed by adjuvant radiation remained the mainstay treatment modality with 81 (62%) patients. Nineteen (15%) patients were treated with surgery alone and 30 (23%) patients with locally advanced surgically inoperable tumors received radiation only. Forty one (32%) patients failed the treatment (local 12, regional 11, locoregional 5, distant 13). The expected 5 year DFS and OS were 65% and 74% respectively. On multivariate analysis, grade was the only independent predictor of DFS and nodal involvement was the only independent predictor of overall survival. Conclusions: Employing existing standards of treatment, comparable survival can be achieved in Pakistani population with major salivary gland malignancies as elsehwere in the world.

• Radiation Oncology Journal
• /
• v.32 no.2
• /
• pp.63-69
• /
• 2014

Purpose: To find the applicability of adjuvant radiotherapy for extrahepatic bile duct cancer (EBDC), we analyzed the pattern of failure and evaluate prognostic factors of locoregional failure after curative resection without adjuvant treatment. Materials and Methods: In 97 patients with resected EBDC, the location of tumor was classified as proximal (n = 26) and distal (n = 71), using the junction of the cystic duct and common hepatic duct as the dividing point. Locoregional failure sites were categorized as follows: the hepatoduodenal ligament and tumor bed, the celiac artery and superior mesenteric artery, and other sites. Results: The median follow-up time was 29 months for surviving patients. Three-year locoregional progression-free survival, progression-free survival, and overall survival rates were 50%, 42%, and 52%, respectively. Regarding initial failures, 79% and 81% were locoregional failures in proximal and distal EBDC patients, respectively. The most common site was the hepatoduodenal ligament and tumor bed. In the multivariate analysis, perineural invasion was associated with poor locoregional progression-free survival (p = 0.023) and progression-free survival (p = 0.012); and elevated postoperative CA19-9 (${\geq}37U/mL$) did with poor locoregional progression-free survival (p = 0.002), progression-free survival (p < 0.001) and overall survival (p < 0.001). Conclusion: Both proximal and distal EBDC showed remarkable proportion of locoregional failure. Perineural invasion and elevated postoperative CA19-9 were risk factors of locoregional failure. In these patients with high risk of locoregional failure, adjuvant radiotherapy could be considered to improve locoregional control.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.5 s.236
• /
• pp.663-670
• /
• 2005

DIN CK35 (JIS S35CK) steels have been used as a material in fuel pump blocks for marine engines. Failures in the inner surface of a drilling hole, due to the initiation of fatigue cracks have been frequently reported. However, the mechanism initiating these cracks and growths has not been clearly diagnosed yet. This study was conducted using a scraped fuel pump block, containing an initiated fatigue crack in the inner surface of a drilling hole. Initially, the cracks and fractured surfaces inside the block were investigated using an optical microscope and a SEM (Scanning Electron Microscope). In addition, microstructure observation, fatigue life test and fatigue crack growth test were performed using a specimen, which was taken from the same block. Results from these tests are summarized as follows; (1) The early crack in the block was supposed to occur inside the inner surface of the drilling hole. (2) The fatigue endurance of this material was about 330 Mpa. (3) The early crack was generated in the cavitations created by the breakdown of a big inclusion, or separation between the big inclusion and the base metal, in which the fundamental ingredients of the inclusion were C, 5, and Mn. (4) In order to prevent these types of failures, the suppression of inclusions inflow by improving the casting process, formation of fine inclusions by applying a heat treatment process, and coating of the surface of the drilling hole were required.

• Radiation Oncology Journal
• /
• v.12 no.3
• /
• pp.331-336
• /
• 1994

Purpose : To assess the effectiveness and problems of the primary radiation therapy and salvage surgery in a series of patients affected by T1-T2NO glottic cancers treated from 1985 to 1991 at the Pusan National University Hospital. Materials and Methods : From 8/85 to 12/91,34 patients affected by early glottic carcinoma histologically proven were treated with curative radiation therapy, Distribution of patients according to T stage was 30 for T1 and 4 for T2. Male to female ratio was 33:1. Age of patients ranged from 31 to 73 with mean age of 58 years. All of the patients were treated with radical radiation with total tumor dose of 63-75. 3Gy(median 68.2Gy), of 5 weekly fractions of 1.8-2Gy and with 6MV photon beams through two laterally opposed fields. Results : The overall 5-year local control rates were $74\%$(8/30) for Tl, and $25\%$(3/4) for T2. The main cause of failure was progression or recurrence in T(10/11). One failures were observed in T and N at the same time. Of these 11 patients, 9($81\%$) were salvaged with surgery, After surgical salvage of radiation failures, the 5-year survival rates were $96\%$ for T1 and $75\%$ for T2. Among the survivors, $73\%$ of T1 and $33\%$ of T2 were able to preserve the larynx. Conclusion : It can be concluded that radiotherapy is the first choice in the treatment of glottic T1 carcinoma.

• Restorative Dentistry and Endodontics
• /
• v.21 no.1
• /
• pp.267-279
• /
• 1996

Microorganisms are implicated the endodontic treatment failures. Persistent endodontic infection may be the result of retention of microorganisms in the dentin of the root canal walls. Dentinal tubules of the root canal walls have been shown to harbor microorganisms. The purpose of this study was to investigate the invasion of microorganism into the root dentin and dentinal tubules. The effects of irrigation solutions and smear layer on bacterial colonization of root canal were evaluated using a scanning electron microscopy. Canals of extracted human teeth with single and straight canals were stepback prepared using normal saline. Tooth samples were divided into four groups according to the irrigation solutions -5 % sodium hypochlorite and normal saline-and smear layer treatment. The smear layer was removed by 5% NaOCl and 20% EDTA for 10 min respectively. After sterilization, they were incubated with each strains of Streptococcus sanguis, Enterococcus faecalis, Staphylococcus aureus and Escherichia coli. Sodium hypochlorite solution reduced the adhesion of microorganisms effectively compared to normal saline. The smear layer inhibited colonization of E. faecalis, S. aureus and E. coli in the root canals due to their blocking of dentianl tubules. But S. sanguis invaded dentinal tubules in the root canals without smear layer. It was suggested that bacterial attachment might be different according to the strains. Sodium hypochlorite inhibited bacterial attachment in the dentinal tubules dramatically. The absence or presence of smear layer affected bacterial invasion of the dentinal tubules.

• Journal of Gastric Cancer
• /
• v.18 no.1
• /
• pp.1-19
• /
• 2018

Gastric cancer (GC) is the second leading cause of cancer mortality and the fourth most commonly diagnosed malignant diseases. While continued efforts have been focused on GC treatment, the introduction of trastuzumab marked the beginning of a new era of target-specific treatments. Considering the diversity of mutations in GC, satisfactory results obtained from various target-specific therapies were expected, yet most of them were unsuccessful in controlled clinical trials. There are several possible reasons underlying the failures, including the absence of patient selection depending on validated predictive biomarkers, the inappropriate combination of drugs, and tumor heterogeneity. In contrast to targeted agents, immuno-oncologic agents are designed to regulate and boost immunity, are not target-specific, and may overcome tumor heterogeneity. With the successful establishment of predictive biomarkers, including Epstein-Barr virus pattern, microsatellite instability status, and programmed death-ligand 1 (PD-L1) expression, as well as ideal combination regimens, a new frontier in the immuno-oncology of GC treatment is on the horizon. Since the field of immuno-oncology has witnessed innovative, practice-changing successes in other cancer types, several trials on GC are ongoing. Among immuno-oncologic therapies, immune checkpoint inhibitors are the mainstay of clinical trials performed on GC. In this article, we review target-specific agents currently used in clinics or are undergoing clinical trials, and highlight the future clinical application of immuno-oncologic agents in inoperable GC.

• The Journal of the Korean dental association
• /
• v.53 no.5
• /
• pp.307-317
• /
• 2015

Although the long-term success of osseointegrated endosseous implants for the support of fixed dental prostheses has been reported, the increasingly widespread use of implant-supported prostheses has led to problems associated with their structural integrity. The most common biomechanical complications observed in dental implant treatment are fracture and screw loosening. The nature of loosening or fracture of dental implant components is complex, since it involves fatigue, fitness, and varied chewing patterns and loads. To assess the service life of the components of the prosthetic system, a knowledge of the loads transmitted through the system is necessary. Design of the final restoration and occlusion in relation to the geometry of a prosthetic restoration has a great influence on the mechanical loading of the implant. It is proposed that control of force in oral cavity may play a larger role in failures than previously believed. Based on theoretic consideration and clinical experiences with dental implant, this article gives simple guidelines for controlling these loads.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.12 no.4
• /
• pp.93-99
• /
• 2013

Parts and structures such as piston rod and knuckle joint for the use of hydraulic cylinder are often welded together in some fashion, usually due to cost and process effectiveness. Welding strongly affects the material by the process of heating and subsequent cooling as well as by the fusion process with additional filler material. Furthermore, a weld is usually far from being perfect, containing inclusions, pores, cavities, undercuts etc. As a consequence, fatigue failures appear in welded structures mostly at the welds rather than in the base metal, even if the latter contains notches. For this reason, fatigue analyses are of high practical interest for all welded structures under the action of cyclic loads. This paper describes the influence of welding parameters, material combinations and heat treatment on the fatigue behavior of welded cylinder rod. In addition, statistical characterization of stress-life response in weldment of hydraulic cylinder rod are presented.