130 research outputs found
Prognostic role of PET/CT in endometrial cancer
Objectives: The present study evaluates the prognostic value of metabolic parameters related to the primary tumor identified in preoperative fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) scans in patients with endometrial cancer (EC).
Material and methods: This study included 120 patients with EC who underwent PET/CT in the preoperative period. The patients’ age, maximum standardized uptake value (SUVmax), SUVmean, metabolic tumor volume (MTV) and the total lesion glycolysis (TLG) value of the primary tumor on PET/CT; as well as the stage, histological subtype, grade and size of the primary EC; the degree of myometrial invasion (MI) cervical invasion (CI), lymphovascular invasion (LVI), lymph node metastasis (LNM) and distant metastasis (DM) were all recorded. The relationship of these factors with progression-free survival (PFS) and overall survival (OS) was evaluated.
Results: The study included 120 patients with EC with a mean age of 62.3 ± 0.02 years. Of the total, 32 patients died around the time of the analysis and 38 patients showed disease progression. The mean OS was 32.7 ± 1.6 months and the mean PFS was 30.5 ± 2.8 months. No significant relationship was identified between the SUVmax, SUVmean, MTV, TLG values, patient age, tumor size, histology, grade and MI degree, and OS or PFS. Disease stage, LVI, CI, LNM and DM were identified as prognostic factors for OS and PFS.
Conclusions: The present study found no significant relationship between preoperative PET parameters in EC and OS and PFS, although prospective studies involving a larger number of patients are required.
The value of PET/CT in determining lymph node metastasis of endometrial cancer
Objectives: In our study, the role of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in determining lymph node metastasis of endometrial cancer was evaluated.
Material and methods: The present retrospectively registered study included 80 patients with endometrial cancer who underwent PET/CT in preoperative period. The patients underwent total hysterectomy with bilateral salpingo-oophorectomy and lymph node dissection. Lymph node status was evaluated in histopathologic examination and PET/CT imaging and, the results were compared.
Results: There were 80 patients (mean age 62 years) in the present study. Lymph node metastasis was detected in five patients, whereas 75 patients had no lymph node metastasis. A total of 1,471 lymph nodes were examined histopathologically, revealing benign findings in 1,433 (pelvic = 1018, paraaortic = 415) and malignant findings in 38 (pelvic = 28, paraaortic = 10) lymph nodes. The accuracy, sensitivity and specificity of PET/CT in determining lymph node metastasis was 95%, 80% and 96% in patient-based evaluation, and 97.4%, 78.9% and 98.6% in lymph node-based evaluation, respectively. The detection sensitivity of PET/CT was 0%, 81.4% and 100% in metastatic lymph nodes with a short diameter of ≤ 4 mm, 5–9 mm and ≥ 10 mm, respectively. PET/CT could detect 73.3% of metastatic lymph nodes that had < 10 mm short diameter.
Conclusions: PET/CT is useful method in detecting lymph node metastasis especially that are disregarded by CT or MR in endometrial cancer. Although PET/CT doesn’t fully replace the surgical staging, its utilization in preoperative period may guide surgical procedure
Performance based study on the seismic safety of buildings
In the scope of this study, information has been provided on the Static Pushover Analysis which is a nonlinear deformation controlled analysis method and the Capacity Spectrum Method used to determine the performance point. In this study, static pushover analysis was made on a six-storey building with reinforcement concrete frame system by changing the materials, steel rebars and soil characteristics. The building’s capacity curves were drawn and decided according to different concrete and reinforcement groups. Furthermore the performance points of different classes of concrete were studied according to three seismic effect levels. In the case of a decrease in the reinforcement strength, a decrease of approximately 30% occurs in the base shear force. If the concrete strength is increased, an increase of 11% occurred in the base shear force. Consequently, in the comparisons made with five different concrete groups and two different reinforcement groups, rather than the increase in the strength of the concrete, an increase in the reinforcement strength was observed to be more effective on the structural capacity. Furthermore, local soil classifications were observed to be the most significant point regarding peak displacement
An experimental study on impact of anchor bars at the steel frames with infilled walls
In this study, a series of experimental study was conducted to investigate the effect of anchor bars on steel frame systems where the connections were provided by anchor bars between frame and infilled walls. Seven one over four scaled specimens having one story and one bay of frames were tested. Experimental study was carried out by damage-controlled and incrementally applied load up to loading cracks. The test results relieved that with the help of using anchor bars the capacity of energy absorption with initial stiffness were increased. It has been found that the frames without using anchor bars failure at the loading edge, the crushing behavior of infilled walls and separations at free edges were occurred. These observed failure behaviors replies with tensile cracking for the frames having anchor bars. There for it should be underlined that anchor bars have a significant effect on improving the behavior of the frames
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Efficient optimization methods for analog/mixed-signal integrated circuits via machine learning
During the analog design process, a significant amount of human effort is spent on optimizing circuit specifications by tuning the device parameters. Sizing device parameters is the task of obtaining satisfactory performance for certain constraint metrics and minimizing/maximizing other objective metrics. In general, an initial optimization is conducted based on schematic-level electrical simulations. However, the Analog/Mixed-Signal (AMS) Integrated Circuits (IC) design is also sensitive to the parasitics introduced during the layout. Therefore, a more comprehensive approach is to size device parameters under the consideration of layout parasitics. To automate this process, many automation methods are proposed where simulation feedback is integrated into the automation loop for an accurate evaluation of design choices. AMS simulations are typically costly to run; therefore, the automation method's cost is crucial. This dissertation proposes efficient automated solutions to solve the AMS sizing problem. First, this dissertation proposes a novel Machine Learning (ML) assisted evolutionary algorithm to tackle analog sizing problem. We address the data scarcity issue by introducing a data augmentation method that facilitates and improves the modeling of design metrics via Artificial Neural Networks (ANN). Further, we borrow techniques developed for evolutionary algorithms and introduce a parameter-free ranking methodology to differentiate design performance without human input. We assess the performance of our approach on several academic circuits and show that ML-based modeling significantly improves the simulation cost of the optimization algorithm. Second, in this dissertation, we study applying Reinforcement Learning~(RL) to solve analog sizing problem. We are influenced by the state-of-the-art policy gradient methods and tailor them to solve analog sizing task. Further, we include a recipe to extend this method for solving industrial-scale circuits with thousands of devices. We demonstrate the performance of our approach both on academic circuits and industrial circuits. We observe a significant performance improvement compared to several conventional baseline algorithms and compared to existing commercial tools. Then we visit the AMS tasks with varying simulations costs. Motivated by the fact that one typically needs to run multiple types of simulations, we leverage cheap-to-run simulations to make intermediate decisions on the potential quality of explored points. Then we refrain from expensive-to-run simulations if necessary. In addition, we introduce an asynchronously parallel framework and adapt our previous work for the case of designs with the differentiated cost of simulations. Our benchmarking shows that the proposed methods significantly reduce the total real-time optimization cost and the total CPU effort. Finally, this dissertation includes a solution on how to solve the sizing problem under layout effects effectively. We conduct a study to quantify the impacts of considering layout during transistor sizing. Then, we apply a Bayesian Neural Network~(BNN) based approach to solve the sizing problem. To include layout-induced parasitics, we extend our approach via Multi-Fidelity BNN, where the algorithm utilizes multiple information sources for efficient learning of post-layout performances. We also include a search-space exploration strategy using the trust-region approach, which is shown to be effective on problems with high number of input dimensions. Our tests suggest that the BNN-based sizing algorithm is very competitive compared to previous state-of-the-art algorithms. We further demonstrate that the co-learning strategy of Multi-Fidelity BNN further improves the efficiency, which is very crucial considering the costly post-layout simulations.Electrical and Computer Engineerin
Numerical investigation of reinforced concrete frame behavior subjected to progressive collapse
Progressive collapse is defined as the spread of an initial local failure of a structure. This phenomenon, caused by the removal of one or more load-bearing element, is followed by a chain of failures through the structure and ultimately leads to partial or even full collapse of an entire structure. As a result, an accurate understanding of structural behavior subjected to large displacements, caused by progressive collapse, is essential to ensure a safe structural design. A progressive collapse in buildings often starts with the removal of one or more columns and continues with the collapse of adjoining structural elements. Experimental studies on progressive collapse are generally not recommended because of its cost and safety reasons. Today, as a result of progress in computer technology, more complicated problems can be investigated numerically. In this study, a numerical model is used for nonlinear analysis of a reinforced concrete (RC) frame behavior subjected to progressive collapse. It is obtained that there is a good agreement between the results with those of the experimental study given in the literature. According to the results, it can be predicted numerically the response of an RC frame to progressive collapse at a highly accurate level
The prognostic significance of serum CA125 levels with ER, PR, P53 and Ki-67 expression in endometrial carcinomas
Objectives: The present study evaluates the relationship between the expression levels of hormone receptors (HRs), Ki-67, p53 and serum cancer antigen 125 (CA125) levels in endometrial cancer and clinicopathological risk factors, and determines their prognostic values. Material and methods: This retrospective study included 49 patients with endometrial cancer whose estrogen receptor (ER) and progesterone receptor (PR) Ki-67 and p53 expression levels were determined through immunohistochemical methods, and whose preoperative serum CA125 levels were measured. These factors relationship with various clinicopathological factors, progression-free survival (PFS) and overall survival (OS) was investigated. Results: The study included 49 patients with EC with a mean age of 61 ± 10 years. The rate of HR positivity was significantly higher in the endometrioid histology group than in the non-endometroid histology group (p = 0.026). A high level of Ki- 67 expression was found to be associated with a non-endometroid histology (p = 0.016), and a high tumor grade (p < 0.001) and a high p53 expression were found to be associated with advanced disease stage (p = 0.026). A positive correlation was found between p53 and Ki-67, a negative correlation was found between p53 and Ki-67 and the presence of HR. Significant relationship was not found between HR status, p53, Ki-67, CA125 and either other clinicopathological risk factors or survival. Conclusions: While HR positivity indicates favorable clinicopathological prognostic factors, high Ki-67 and high p53 expression indicate unfavorable ones. However, no direct effect of these factors on prognosis was found in this study
The effect of linear guide representation for topology optimization of a five-axis milling machine
Topology optimization is a countermeasure to obtain lightweight and stiff structures for machine tools. Topology optimizations are applied at component level due to computational limitations, therefore linear guides’ rolling elements are underestimated in most of the cases. Stiffness of the entire assembly depends on the least stiff components which are identified as linear guides in the current literature. In this study, effects of linear guide’s representation in virtual environment are investigated at assembly level by focusing on topology optimization. Two different contact models are employed for rolling elements in the linear guides. Reliability of the contact models are verified with experiments. After the verification, heavy duty cutting conditions are considered for the system and topology optimization is performed for two different contact models to reduce the mass of the structure. The difference caused by the representation of rolling elements is demonstrated for the same topology algorithm and the optimization results are compared for the models. Lastly, the effect of using more stiff linear guides in the five-axis milling machine is investigated by increasing the stiffness of the contact elements
Comparison of polymethylmethacrylate versus hydrophobic acrylic lenses for primary intraocular lens implantation in pediatric cataract surgery
AIM: To compare the visual results and postoperative complications of polymethylmethacrylate(PMMA)and hydrophobic acrylic intraocular lenses(IOLs)in children who underwent cataract extraction with primary IOL implantation.METHODS:This retrospective study included 117 eyes of 63 children with bilateral pediatric cataract undergoing cataract surgery and primary IOL implantation. The patients were divided into two groups, Group I included 58 eyes of 30 patients with PMMA IOLs; Group II included 59 eyes of 33 patients with hydrophobic acrylic IOLs. The clinical features, refraction errors, best corrected visual acuity(BCVA)and surgical complications were compared between two groups.RESULTS:The mean age at the time of surgery was 5.8(2-12)y and mean follow up period was 40.5(6-196)mo. Postoperatively, BCVA was ≥0.5 in 80 eyes(68.4%)and this was comparable in two groups. Visual axis opacification was seen in 28 eyes(48.3%)in Group I and 16 eyes(27.1%)in Group II and this difference was statistically significant(P=0.018). Postoperative IOL dislocation and posterior synechia formation were also noted. When all postoperative complications were considered, there were significantly less complications in the acrylic IOL group than PMMA IOL group(P=0.020).CONCLUSION: Pediatric cataract surgery with primary IOL implantation is a safe procedure. Hydrophobic acrylic IOLs may lead to less postoperative complications compared to PMMA IOLs
Can proliferative hypertrophic scars of the median sternotomy incision predict the occurrence and characteristics of urethral stricture?
Conclusion: A poorly healed median stemotomy incision scar can predict a poor wound healing in the urethra tissue. Further large scale, multi-center and prospective studies are needed to clarify this relationship
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