Browsing by Author "Ahmad, A."
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Conference paperPublication Metadata only Calibration of 2D ultrasound in 3D space for robotic biopsies(IEEE, 2015) Ahmad, A.; Çavuşoğlu, M. C.; Bebek, Özkan; Mechanical Engineering; BEBEK, ÖzkanFreehand Ultrasound technique is widely used in intraoperative biopsy procedures for detecting the volumes of interest. Freehand ultrasound probe is faster and flexible with 6 degrees of freedom. Thats why the imaging system must be calibrated in 3D space before integrating it with Robotics Biopsy System. In this paper we present a 3D space calibration method using a multipoint cross-wire phantom. The Ultrasound probe is attached to a robotic manipulator arm which moves it over the phantom in precise steps of distances and angles. The position and orientation of the probe is tracked by an optical tracking system. Optical markers are placed on the probe, phantom tank and the validation needle. The optical tracking system returns the position and orientation of the reference frames attached to these optical markers. The location of threads with reference to the frame of Ultrasound probe is found using this information. These values and the values returned by a mathematical model of the calibration box are used to construct the calibration matrix. The whole system is automated so it can process high number of frames which makes it rapid and more accurate. This process is used to calibrate the space for an automated needle insertion biopsy robot. The accuracy of the system was checked by a validation needle in 3D space. RMS error of the experiment groups on average was 1.67mm.Conference paperPublication Metadata only Design and kinematics of a 5-DOF parallel robot for beating heart surgery(IEEE, 2019) Ersoy, Onur; Yıldırım, Mehmet Can; Ahmad, A.; Yirmibesoglu, O. D.; Koroglu, N.; Bebek, Özkan; Mechanical Engineering; BEBEK, Özkan; Ersoy, Onur; Yıldırım, Mehmet CanIn this paper, mechanical and electronics design of a lightweight 5-DOF robot, Ozyegin Surgery Robot I (OSI), and it's performance of tracking the heart motion for coronary artery bypass procedure (CABG) are presented. The OSI is designed to operate for high motion bandwidths. This ability is realized using 3 sub-mechanisms: a 3-DOF remote stage for high acceleration, a 2-DOF fixed stage for low error positioning, and a drive unit to actuate 3-DOF surgical tools. The forward and the inverse kinematics of the OSI's sub-units are also presented. The transmission ratios (gear ratios) and initial angle offsets of the robot are calibrated using an optical measurement sensor. The ability of the robot to track the beating heart motion is tested using simulations and experiments. The results show that the robot end-effector can track the heartbeat motion data with 0.66 mm error.Conference paperPublication Metadata only High-performance work systems and organizational performance across societal cultures(Springer, 2018) Dastmalchian, A.; Bacon, N.; McNeil, N.; Steinke, C.; Blyton, P.; Kumar, M. S.; Bayraktar, Seçil; Auer-Rizzi, W.; Ahmad, A.; Craig, T.; Isa Ghazali Bin Musa, C. R. B.; Habibi, M.; Huang, H. J.; Imer, P.; Ayman, I.; Kabasakal, H.; Meo Colombo, C.; Moghavami, S.; Mukherjee, T.; Tang, N.; Thang, T. N.; Varnali, R.; International Business and Trade; BAYRAKTAR, SeçilThis paper assesses whether societal culture affects the relationship between human resource management practices and organizational performance. Drawing on matched employer-employee data from 387 organizations and 7,187 employees in 14 countries, the findings show a positive relationship between high-performance work systems (HPWS) and organizational performance across societal cultures. This relationship was not moderated by three dimensions of societal culture (power distance, in-group collectivism, and institutional collectivism) as proposed by contingency models of culture fit. However, further examination of three dimensions of human resource systems (skill-enhancing, motivation-enhancing, and opportunity-enhancing practices) revealed that opportunity-enhancing practices appear less effective in high power distance cultures. The findings provide general support for the universalistic ‘best practice’ perspective with regard to the positive relationship between HPWS and organizational performance, tempered by an appreciation of the limitations to opportunity-enhancing practices in high power distance cultures.ArticlePublication Metadata only Visual needle tip tracking in 2D US guided robotic interventions(Elsevier, 2019-02) Kaya, M.; Şenel, E.; Ahmad, A.; Bebek, Özkan; Mechanical Engineering; BEBEK, ÖzkanPercutaneous needle procedures are among the most frequently performed minimally invasive surgical procedure. For tracking the needle tip in the tissue, 2D ultrasound (US) imaging is commonly used; however, the low resolution of the images creates a challenge for tracking. This paper describes a robotic system that can perform US image guided biopsies by tracking the needle and the target simultaneously. It uses a template-based visual tracking method for small and deformable targets. During the experiments, a needle was inserted into realistic phantoms using a 5-DOF robot. The 2D US probe was held by a robotic arm that was servoed along the needle path. The 3D shape of the needle was estimated using the 2D transverse US images, which was used to align the needle axis with the 2D imaging plane. The accuracy of the visual needle tip tracking was evaluated using an optical tracking system, and a computed tomography scanner was used to determine the accuracy of the 3D needle shape estimation method. Target reaching accuracies were measured using an electromagnetic tracking system. The results of the experiments showed that the proposed system can track the needle tip in 2D US guided needle procedures in real-time with a sub-millimeter positional error.