M.S. Theses

Permanent URI for this collection

https://digitalarchive.library.bogazici.edu.tr/handle/123456789/11717

Browse

Now showing 1 - 20 of 348

1940-nm thulium fiber laser ceramic bracket debonding
(Thesis (M.S.) - Bogazici University. Institute of Biomedical Engineering, 2012., 2012.) Demirkan, İrem.; Gülsoy, Murat,
The aim of the study was to determine the proper laser paramaters for 1940-nm Thulium Fiber Laser for ceramic bracket removing. In order to assess the e ectiveness of 1940-nm Thulium Fiber Laser in orthodontic ceramic bracket debonding , polycrystalline ceramic brackets were bonded to mandibular bovine teeth with adhesive agent.The samples were divided into 9 di erent groups due to applied laser power and laser duration, debonding method used . There was a control group that had no laser application . The e cency of the laser was investigated together with the required debonding forces and intrapulpal temperature changes . In this study, keeping intrapulpal temperature changes below the threshold value that is accepted 5; 5 C must be accepted as a must. In most of the lasing groups , the increase in intrapulpal temperature changes were observed almost below the threshold value 5; 5 C . The ndings revealed that 1940-nm Thulium Fiber Laser irradiation could reduce the needed debonding force or SBS (shear bond strength ) values signi cantly compared to control group . Irradiation of the specimens by 1940-nm Thulium Fiber Laser caused more than 50% reduction in the needed debonding force when compared to the control group. Di erent application methods : non-scanning and scanning were studied to assess the e ects of the distinct con gurations. Scanning method was tried to reduce the intrapulpal temperature rise during laser irradiation but in this study side e ects of this method were faced. It was revealed that di erent application methods did not create any remarkable di erences . In more than 50% of samples with energies 25 J or more, adhesive remnant hasn't been observed on enamel surfaces for the laser groups.|Keywords : Laser, Debonding, Ceramic Brackets.
3 D display of organs using CT data implementation on an IBM PC
(Thesis (M.S.)- Bogazici University. Institute of Biomedical Engineering, 1987., 1987.) Hüner, Mutlu.; Güveniş, Albert.
This thesis presents a low cost software package for the three dimensional display of organs using an IBM microcomputer.First existing 3D display techniques and their application in medicine are given. Then the particular algorithm selected for implementation is described and explanations pertinent to this specific implementation are discussed. The boundary detection algorithm used is the one developed by G.T. Herman et,al, Standard computer graphics methods displaying 3D objects. A grid technique is are used introduced for when performing the scan conversion in orter to increase image quality. Some of the results obtained by using mathematical phantoms are presented and discussed. The results indicate that this package can display high resolution images withoul antialiasing effect that is typically encountered in similer packages. It is shown that low pass filtering is only needed in extreme cases.
3D-printing technique for fabrication of biodegradable PDLLA tympanostomy tube and examination of biofilm formation
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2021., 2021.) Güner, Dine.; Güçlü, Burak.; Ege, Duygu.
In this study, it is presented that the new fabrication method for biodegradable PDLLA tympanostomy tube by examining its degradation and swelling behavior, bacterial attachment, and biofilm formation with a comparison of Fluoroplastic one. The novelty of the study lies in the 3D printing fabrication technique. No research work studied the fabrication of samples in these dimensions (2 mm in length) and design. The samples are printed at 190 ◦C temperature under 7.9 bar pressure with 0.1 mm/min speed. The fabrication of one sample took 9 minutes with a 0.3 mm nozzle, and structural collapsing was able to be prevented. After the fabrication of 3D-printed PDLLA samples, they are examined for the degradation and swelling characteristics at 37 ◦C in PBS for 5 weeks. The degradation rate of 3D-printed PDLLA samples is 5%, and the swelling ratio is 40 % for 5 weeks. Scanning Electron Microscopy (SEM) was used for the surface examination, and results showed that PDLLA samples have fewer surface faults than control group of Fluoroplastic tubes in microscale level. For examining bacterial attachment on the layer-by-layer surface of the PDLLA sample, a biofilm assessment was done for 4 days. According to colony counting and CFU/mL results, 3D-printed samples had less biofilm formation despite the layered surface structure coming from the fabrication process. Overall, biodegradable tympanostomy tube fabrication by using the 3D-printing technique needs to be improved. However, according to experimental results, if the fabrication method can be improved to produce more precise structures in that dimension, it is possible to further this study to produce more perfectly tympanostomy tubes.|Keywords : 3D-printing, Poly-lactic acid, biodegradable implant, bacterial attachment, tympanostomy tube, otitis media.
A comprehensive medical equipment management software system for increased patient safety
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2019., 2019.) Akar, Neslişah.; Öztürk Işık, Esin.
A medical equipment system was developed to include the inventory of medical equipment, the failure management process, the maintenance and repair periods, the management and the scheduling for calibration and preventive maintenance. The software system keeps all necessary information, analyzes and converts this information intomeaningfulresultsandgraphicalcharts. Itcanreportthefailuretypes, theleading causes for the failures, and the cost analysis for each failure. The user determines the frequency for the preventive maintenance according to this information. Scheduling makes it easier to control and stick by the layout of the hospital process. This webbased software project was written by Entity Framework code ﬁrst system in ASP.NET MVC 5 area on SQL server 2016 database, which was created on the Microsoft Azure Cloud System server. The upgrades and maintenance of the system could be done while the system is operational. The screens are limited by access authorization of each type of user.|Keywords : Medical Equipment Management System, Preventive Maintenance, Analyze.
A computer aided biofeedback system
(Thesis (M.S.) - Bogazici University. Institute of Biomedical Engineering, 1986., 1986.) Aybey, İ. Melih.; Güveniş, Albert.
Biofeedback devices, unlike other medical devices, are not used in order to monitor a disordered physiological function. They are aimed to be used in training work to gain control over any physiological variable which may have no direct relation with the symptoms of the illness. This thesis reviews the theory and applications of biofeedback and presents an original design of a computerized biofeedback system (DBMl. The digital biofeedback monitor is a system which enables the therapist to analyze the data obtained during and after a biofeedback session by means of a digital computer. It can also be used by the patient for any kind of biofeedback treatment. Collected data related to the session can be stored onto a floppy disk for future references and analyses.
A correlational stydy between serum cytokine measures, volumetric MR measures and global cognitive changes in Alzheimer's disease
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2010., 2010.) Tardu, Mehmet.; Ademoğlu, Ahmet.; Gürvit, Hakan.
Earlier detection and diagnosis of Alzheimer's disease (AD) would permit earlier intervention, which conceivably could delay progression of this dementing disorder. In order to accomplish this goal, reliable and speci c biomarkers are needed. Unfortunately, there is no yet such a universally accepted biomarker. In this study, we aimed to analyze the association between volumetric MR measurements and possible AD related serum cytokine biomarkers and to determine biological and clinical predictors for patients at high risk to develop AD. 28 AD patients and 16 healthy controls were participated to the study. For this study biochemical markers (IL-1 , IL-1 , IL-10, TNF- ) which were considered to play a pivotal role in the in ammation process during AD were chosen. Additionally, volumetric MR measurements were done to determine atrophic regions in the brain of AD patients. For this purpose, a fully automated software (FreeSurfer) was used. First of all, our ELISA measurements indicated that patients with AD produce increased quantities of pro-in ammatory cytokines (IL-1 and TNF- ) than normal subjects and these results supporting the hypothesis that a pro-in ammatory phenotype contributes to AD. ROC curve analysis showed that IL-1 and TNF- serum levels could not be used as a diagnostic test tool. However, serum IL-1 level might be a better candidate to make a better diagnostic decision. Secondly, regression analysis revealed that serum IL-1 level had a signi cant linear relation with the volume changes of cerebral white matter and amygdala/hippocampus. Additionally, the Mini-Mental State Examination (MMSE) score was used as a scale of AD severity. Regression analysis emphasized that serum cytokine levels did not have a signi cant relation with the severity of cognitive impairment.|Keywords: Alzheimer's Disease, Biomarker, Serum, In ammation, IL-1alpha , IL-1beta , IL- 10, TNF-alpha , Volumetric MR, FreeSurfer, Mini-Mental State Examination
A database management system for nuclear medicine
(Thesis (M.S.) - Bogazici University. Institute of Biomedical Engineering, 199., 1985.) Dentes, Selim.; Miller, Neil,
The purpose of this thesis is to develop a databank of Nuclear Medicine activities in Turkey. Until recently, no databanks existed in any field in Turkey. This was because the available technology was insufficient to establish such databanks. As a result, obtaining specific information about a subject in any field was time consuming and expensive. However, today, the facilities exist to construct databanks and extensive work has been done to computerize and establish databanks of birth certificates, police records and other information. The purpose of this thesis is to establish such a databank in Nuclear Medicine. This system is meant to be used by all physicians (both Nuclear Medicine physicians and non- Nuclear Medicine ones), Nuclear Physicists, chemists, University Biomedical students and staff, equipment suppliers and government agencies. Primarily, it will be most helpful to physicians in the eastern part of Turkey, where Nuclear Medicine centers are not available and for physicians who can not follow the recent developments taking place in this field in Turkey. This thesis consists of two parts. The first describes the field of Nuclear Medicine. It has three sections. The first is a detailed description of the gamma camera, the second describes the isotopes and radiopharmaceuticals used in Nuclear Medicine imaging, and the third, Nuclear Medicine studies. The second part of the thesis describes the database manager program, PC-FILE III, used to organize the data collected from Nuclear Medicine centers. It also has three sections. The first section describes how the database was designed, i.e. file definitions, data collection and distribution between them are given. The second section discusses the use of the database manager, and the last provides a detailed report derived from the database. The thesis is concluded with examples of how the system is used, how it can be extended for future needs and the advantages and disadvantages of the system.
A device for functional and cosmetic improvement of lagophtalmos due to facial paralysis
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2009., 2009.) Aşık, Mehmet Doğan.; Güçlü, Burak.
A new device for the correction of eyelid problems due to facial palsy was studied. Lagophthalmos is the condition of the paralyzed eyelids' to close totally. It may cause drying and irritation .In this thesis, 14 rabbits were injected with local anaesthetics to induce temporary facial palsy and lagophtalmos. In order to provide functionality to the upper eyelids, ferromagnetic steel pieces were placed inside and outside of the eyelids of the rabbits. The device moves the eyelids by magnetically pulling the steel pieces. The control group (n=5) did not wear the device.The treatment group with external implant (n=4) and the treatment group with internal implant (n=5) made to wear device and tested. All animals were observed during the experiments and recorded to video tapes. The data collected from video records were analyzed to test the statistical di erence between control and the treated groups. The results showed that treatment groups paralyzed eye and control groups paralyzed eye have signi cant di erences. Furthermore, the treatment group with internal implant shows a noticeable similarity with the healthy(un-paralyzed) eye.|Keywords: Lagophtalmos, Facial Palsy, Implant, Medical Device, Rabbit.
A FES device developed for treating drop foot
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2006., 2006.) Yavuz, Aykut.; Gülçür, Halil Özcan.
Multiple sclerosis, stroke and peripheral neural disorders affect the centralnervous system and cause various nervous and muscular disabilities. One of thesedisabilities is called drop foot, which prevents the patient from raising the foot at the ankle and effectively swinging the leg when walking. This situation can be corrected by using muscle stimulators and synchronizing functional electrical stimulation of thecommon peroneal nerve to the swing phase of the gait cycle.This thesis presents a portable, two channels, functional electrical stimulator that was designed and developed to assist drop foot patients during walking. The device has two independently programmable constant current outputs, which can produce biphasicpulses having pulse with up to 350 us and amplitude up to 100 mA. A microcontroller core controls all of the parameters. A new program code has been written for controlling stimulation parameters and storing them for a future application. The system can be programmed using push buttons and an LCD display. A foot switch worn by the patient, under the heel, is used for getting feedback control for stimulation timing during the gaitcycle. This foot switch triggers the output channels to stimulate the related musclesthrough electrodes that are placed over the nerves. Various tests have shown that our system is reliable and the performance of the design is satisfactory enough.|Keywords: Functional electrical stimulation, drop foot, muscle stimulation.
A fiducial-based automatic registration method for X-ray imaging fused with MRI
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2008., 2008.) Sönmez, Merdim.; Öztürk, Cengizhan.
X-ray fluoroscopy is widely used in image-guided interventions especially in catheter-based interventions. X-ray fluoroscopy provides high temporal and spacial resolution, but it suffers from low soft tissue contrast. On the other hand, magnetic resonance imaging (MRI) offers excellent soft tissue contrast and 3D anatomical information. X-ray fused with MRI (XFM) is a system which combines strengths of both image modalities to improve the quality of imageguidance and to achieve minimally invasive interventions. In XFM, pre-operative MR images are segmented, 3D structure of target area is reconstructed from these segments, its 2D projection is overlapped on top of live images during x-ray fluoroscopy. Fusion of two images requires registration of two images which could be archived using external fiducial markers attached to skin of patient. In this approach, first markers are detected and located in both image sets, then least square minimization algorithm is applied to complete the registration. The purpose of our study is to extend the currently practiced XFM systems and to allow its translation into a practical clinical setting by making it easier to use. We developed a fully automatic registration system for XFM. This includes automatic segmentation and localization of fiducial markers in both images and finding the correspondence between two point sets, also designing a marker localization system and development of user interface for technical user. In vivo validation of our method was performed in 10 animal experiments. Results show that our method locates markers in high accuracy, finds correspondence between two point sets and completes the registration process.|Keywords: Image-Guided Intervention, Image Registration, X-Ray Fused with MRI, Correspondence Between Point Sets.
A mathematical model for cerebrovascular dynamics
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2010., 2010.) Alptekin, Melis.; Akın, Ata.
Human brain goes through a number of physiological changes in daily life. Some of these changes can be observed with optical imaging methods at near infrared light range. The aim of this study is, by using functional near infrared spectroscopy (fNIRS), with a speci c experimental protocol, estimating the venous compliance and resistance values of the brain by constructing a three-element Windkessel model and observing oxygenation and blood volume with respect to time. For this purpose, 10 healthy volunteers participated and measurements were taken from their prefrontal cortex during the experiment. When the subjects are in supine position, they were asked to move their heads down to their knees and they stayed in this position for 30 seconds. fNIRS signals were analysed to represent right and left hemisphere. Therefore, in each hemisphere, maximum and minimum points of blood volume showed no signi cant di erence for men and women. (left hemisphere: for Vmin; p=0.12, for Vmax; p=0.22; right hemisphere: for Vmin; p=0.073, for Vmax; p=0.074). Without taking sex di erence into account, Vmin and Vmax values of right and left hemisphere are not signi cantly di erent (respectively p=0.22, p=0.069). For compliance values, there is not a meaningful di erence between left and right hemisphere. (p= 0.38). For resistance values between right and left hemisphere, we found a signi cant di erence (p=0.04).Therefore, this study implies that there is not a meaningful di erence in a young subject group with respect to brain hemodynamics and parameters but only the resistance values. This model may be also used in an elderly or diseased group to observe brain hemodynamics.|Keywords: head-down tilt, fNIRS, Windkessel models
A microcontroller based 100 kHz - 1 MHz multi-frequency bio-impedance measurement device
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2008., 2008.) Solmaz, Hakan.; Ülgen, Yekta.
Complex impedance measurement of biological systems is gaining wide popularity in determining the pathological and physiological status of biological tissues in research applications such as; skin hydration, dental decay, body fat content, tissue ischemia, food freshness, blood freshness and etc. The device presented in this study is a four-probe, multi frequency, portable bio-impedance measurement device based on the principles of magnitude-ratio and phase-di erence detection. The system is built with a DDS frequency generator, a voltage controlled current source, two high frequency instrumentation ampli ers, a phase-gain detector and a microcontroller unit. The software for the microcontroller is written and compiled on CodeVisionAVR C Compiler and the microcontroller is programmed on AVRStudio 4. The accuracy and precision of the prototype device are checked against the HP 4284A LCR meter using di erent RC test loads. The results show that the overall percentage error averages of the real and imaginary parts of the complex impedance are 0.80 % and 1.78 % respectively. The Cole-Cole diagrams are generated to obtain the Cole parameters, R0, R1, fc and ® that give valuable information about the physiological status of biological tissues. Those parameters are also checked against the LCR meter. The percentage errors of ® are found to be high due to relatively high phase-di erence detection errors.|Keywords: bioimpedance, magnitude-ratio and phase-difference detection, direct digital synthesis (DDS), Cole-Cole plot, Cole-Cole parameters.
A mobile urine analysis system for homecare
(Thesis (M.S.) - Bogazici University. Institute of Biomedical Engineering, 2013., 2013.) Kahraman, Büşra.; Özkan, Mehmed.
Urinalysis is a remarkable diagnostic technique and an essential part of physical examination used frequently in kidney and urinary tract diseases. Urine reagent strips which are widely used in urinalysis are impregnated with a number of colored reagent blocks or pads separated from each other by narrow bands. The reagents in each block react with speci c components of urine in such a way that the block changes color if the component is present, and the color change produced is proportional to the concentration of the component being tested for. Recent analysis of test strips is perfomed via refractometric devices of the corresponding test strips. In this thesis, a mobile urine strip analyzer called BUSA which can be controlled via both GUIs of MATLAB and Android operation system was designed by using Parallax's color sensor, TCS3200-DB. The fundemental idea behind this design was to form a database which included color data of control solutions of CombiScan 500, 40 patients analyzed by CombiScan 500 in Yeditepe University Hospital and prepared solutions of known pH and glucose amount. 15 patients analyzed by CombiScan 500 were compared to BUSA. Speci city of the results of the comparison for bilirubin, urobilinogen, glucose, protein, blood, nitrite and leukocyte was 1 and for ketone was 0.933. Sensitivty of the results of the comparison for glucose, protein and blood was 1, 0.2 and 1 respectively. pH and speci c gravity were analyzed via Blant Altman method which means and standard deviations were 0.133, 0.5156 and 0.0017, 0.0059 respectively. In conclusion, BUSA is succesful at measuring pH and specific gravity of urine and negativeness of bilirubin, urobilinogen, ketone, glucose, protein, blood, nitrite and leukocytes. In addition, BUSA is successful at detecting positiveness of glucose and blood, except protein.|Keywords : Urinalysis, Color sensor, Android, homecare.
A multi-channel biotelemetry system for the acquisition and processing of respiratory sounds
(Thesis (M.S.) - Bogazici University. Institute of Biomedical Engineering, 2001., 2001.) Çiftçi, Rifat Koray.; Kahya, Yasemin.
Respiratory disorders can be diagnosed by analyzing respiratory sounds produced during breathing. Main tool for physicians to analyze respiratory sounds is stethoscope. Developing a system capable of acquiring and displaying respiratory sounds and performing real-time analysis and classification is a challenging goal for researchers.This study presents a preliminary approach for the telemetry of respiratory sounds. Increasing the reliability and efficiency of the acquisition process of respiratory sounds is aimed. For this purpose, a system with two separate telemetry transmitters placed on the body of the patient and a remote receiver connected to a PC is developed. A radio frequency link is established between the transmitters and the receiver using frequency modulation.Communication between the PC and receiver is supplied via serial port. To control data acquisition process, a user interface is developed. The receiver can be tuned to any of the transmitters with the help of this interface, which provides the user with the choices of listening, recording and displaying data. A microcontroller is responsible for tuning the receiver according to the commands issued by the computer. The respiratory sounds are filtered by high pass and low pass filters having cut-off frequencies at 80 Hz and 2000 Hz, respectively. A sampling frequency of 5 kHz is selected. Data is digitized by an 8-bit analog-to-digital converter.Performance of the system is tested by measuring its response to some pre-defined signals and by recording respiratory sounds from human subjects. Promising results are obtained revealing the feasibility of telemetering respiratory sounds.
A new hardware design for cardiac passive acoustic localization
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2005., 2005.) Civelek, Yahya.; Gülçür, Halil Özcan.
Heart sounds contain valuable information about the function of the heart; expert clinicians can diagnose many heart disorders by listening to these sounds. One dimensional visual representation of heart sounds called phonocardiograms (PCG) are also used to facilitate the diagnosis. Although, PCG is an inexpensive, non-invasive diagnostic technique, it has been neglected until recently because of its limitations and enormous improvements in other diagnostic techniques such as ultrasonography, CT and MRI. Recently, a significant study on PCG was conducted by Y. Bahadırlar and H. Ö. Gülçür [2]; they developed a system which is composed of a specially designed multi-sensor probe in the form of a planar microphone array, precision amplifiers, filters and A/D converters, interface circuitry, a PC and special software and obtained 2-D and 3-D images of estimates of sound producing sites in the heart. The original system called CARDIOPAL (short for Cardiac Passive Acoustic Localizer) had some limitations mostly arising from relatively limited technology at the time. It had no ECG channel, the multi-sensor probe had coupling problems on non-smooth chests. Moreover it used DMA for data transmission, which made the system device-dependent.In the present thesis, a new, easy-to-use and more compact hardware for CARDIOPAL is developed. The new system (CARDIOPAL II) can work on most of the current operating systems without problems and get data more accurately in order to increase image resolution. An ECG channel is added to the system and ECG signals are acquired simultaneously with the sound signals. The acquired data is transferred to a PC using a high-speed USB 2.0 interface. Moreover, a new flexible design is developed to avoid coupling problem of the array for non-smooth chests. CARDIOPAL II is battery-powered; surface-mount technology was used for the design of all electronic circuitry to make the final system smaller, lighter, and more resistant to electromagnetic interference. The device was tested by acquiring signals coming from two point sources. The localization of these sources was achieved. The device was also tested by obtaining data from real subjects. No quality loss from the corner microphones due to the coupling problem was observed. ECG signals were acquired simultaneously and it was observed that the relationship between ECG and sound signals matched with theory.
A novel design of MRI visible prostate biopsy needle
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2017., 2017.) Kasacı, Gökçe.; Kocatürk, Özgür.
A reliable diagnosis is vital to apply the proper treatment for prostate cancer. Conventional prostate biopsy methods have limited accuracy for the diagnosis. Magnetic Resonance Imaging (MRI) provides superior anatomical images of the prostate, o ering precise tumor targeting which in turn increases diagnostic yield. For that purpose, we aimed to develop a novel MRI compatible and visible prostate biopsy needle. The visible distal tip of the needle is expected to provide accurate placement while the proposed biopsy mechanism can reduce the bleeding and infection risk. The prostate biopsy needle has been designed using MRI compatible nitinol hypo tubes and fabricated using an Nd: YAG laser cutting system. Furthermore, the distal tip sharpness and force resistance of the three di erent needle designs were tested in vitro (silicon mold). According to results the needle with high walled biopsy groove was preferable. Equally spaced Iron Oxide (Fe2O3) nano-particle coatings were placed over the distal tip of the outer needle surface to enhance its visibility under real time MRI. The coating concentration and marker size were optimized using di erent MR sequences. MRI visibility experiments indicate that spin-echo acquisitions should be preferred over gradient-echo acquisitions and Fe2O3 coatings with moderate concentrations appear to be more suitable for the passive tracking of penetration depth. The biopsy needle handle also has been designed in Solidworks 2015 and generated using a rapid prototyping system. Finally, the in-vitro performance of the biopsy mechanism was carried out on fresh veal meat. Obtained samples indicate that Nd: YAG laser cutting can be successfully utilized in nitinol needle production and the biopsy handle design provided repeatable successful biopsy sample collections through in vitro trials.|Keywords : interventional MRI, prostate biopsy, biopsy needle, passive device visualization.
A novel left atrial appendage occluder design
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2019., 2019.) Baykan, Almila Ceren.; Kocatürk, Özgür.
Percutaneous left atrial appendage (LAA) occlusion is a viable nonpharmalogical alternative for prevention of thromboembolic stroke in patients with atrial fibrillation (AF), especially for the patients who are unable to respond to oral anticoagulants. However, several device- or procedure-related complications were reported associated with existing implants. The aim of this study is to design and prototype a novel left atrial appendage occluder in order to prevent life-threatening complications. The proposed system allows to reduce LAA sac volume using a distal nitinol anchor while sealing the LAA ostium using a coated nitinol occluder frame. The sealing capability test of the prototyped occluder frame was performed on the phantom system mimicking left atrial with 12-30 mmHg pressure. Results have demonstrated LAA was successfully occluded and suggested that the percutaneous LAA closure with coated nitinol frame is favorable. The mechanical assessments have shown polyurethane is the promising candidate as coating material against other fabrics using in commercially available occluders. As a part of this thesis study, proof-of-concept coaxial catheter delivery system was prototyped to perform delivery and deployment of occluder frame and distal anchor, respectively. Consequently, this study presented a novel occluder design and provided a good starting point for further applications of prototyping.|Keywords : Left Atrial Appendage, Occluder, Atrial Fibrillation, Biomedical Device Design.
A phantom study :|evaluation of a novel three-lumen balloon catheter for threatment of intractable limb ischemia
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2019., 2019.) Tatarlar, Efecan.; Kocatürk, Özgür.
Peripheral artery disease (PAD) is a serious health problem that includes occlusive arterial syndrome. Critical limb ischemia (CLI) which is the most severe form induces extremity gangrene or ulcers extremity rest pain which mostly can lead to limb loss. The most common CLI criteria: (a) 30 mmHg or less toe systolic pressure, (b) 0.4 or less ankle-brachial index (ABI), (c) 50 mmHg or less systolic ankle pressure. In this study, a custom made three lumen catheter (9 Fr) including a distal inﬂatable balloon in between the inﬂow and outﬂow lumen holes was constructed based on Hyper Perfusion Catheter patent (patent no: 2011/07038) owned by Emir Yusuf, MD. The aim of this catheter design is to elevate ankle and/or toe systolic pressures above 50-60 mmHg to promote healing and/or alleviating intractable pain due to intractable ischemia for patients with CLI. To simulate the blood circulation of related anatomy, in vitro CLI model phantom was designed and constructed by using a modiﬁed hemodialysis circuit; a hemodialysis pump and a tube set were used in bypass surgery procedures. 10% aqueous glycerol solution (by weight in water) was used to mimic human blood plasma. The data was collected by a custom-made circuit in real time and all measurements were veriﬁed with industrial certiﬁcated medical devices. In vitro CLI model phantom experiments have shown that it is feasible to elevate the pressure distal to the occlusion (representing ankle pressure) up to 80 mmHg without increasing the systemic pressure in certain conditions.|Keywords : Peripheral Artery Disease (PAD), Critical Limb Ischemia (CLI), Ankle Systolic Pressure, 9 Fr Three Lumen Catheter.
A study on the neuroendocrine hormone levels and psychophysiological parameters in excessive computer game playing young male adults
(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2010., 2010.) Paşaoğlu, Taliha.; Güçlü, Burak.
Excessive gaming may be considered a behavioral addiction similar to gambling. In order to test this hypothesis, the activity of the autonomic nervous system was recorded (heart rate and skin conductance) and neuroendocrine hormone levels were measured (cortisol, dopamine, -endorphin) in 16 subjects who played computer games excessively (>28 hrs/wk) and in 16 subjects who played infrequently (ages: 19-27). ANOVA was used to study the factor e ects. The excessive players had signi cantly higher skin conductance uctuations than non-excessive players. Their mean heart rates were also marginally higher than the heart rates of non-excessive players. For both subject groups, heart rate uctuations were lower in game sessions compared to control sessions. Cortisol levels were found to be decreased in both groups after each session compared to the beginning of the session. In excessive game players, skin conductance uctuations and -endorphin levels were negatively correlated; heart rate mean and dopamine levels were positively correlated. In non-excessive players, skin conductance uctuations and cortisol levels were positively correlated. These results show clear di erences of autonomic responses in excessive game players. Although we could not nd a direct di erence in excessive players regarding hormone levels, correlations show evidence of signi cant changes in their neuroendocrine systems.|Keywords: Computer game addiction, neuroendocrine, cortisol, beta-endorphin, dopamine, psychophysiology, skin conductance, heart rate.
A user-friendly sofware for generating patient-specific masking noise in relieving the incurable tinnitus
(Thesis (M.S.) - Bogazici University. Institute of Biomedical Engineering, 1996., 1996.) Fırat, Murat.; Gülçür, Halil Özcan.
Tinnitus is a widely suffered complaint concerning the human auditory system. The tinnitus-stricken patient is generally characterized with hearing loss and suffers from an almost never-ending sound in his ears. These whistle, wind, water fowl, water flow, hissing, etc.-like sounds are always subjective and thus, their detection is quite difficult. Masking the tinnitus sound is one of the most successful non-invasive methods of coping with the tinnitus. In order for the masking method to be acceptable and successful, the masking sound should be individually tailored for the patient. In this thesis, a special computer software has been improved which will enable the physician to detect the tinnitus frequency necessary for masking and which will especially be learnt and conducted easily by the patients. Such a system, consisting of a PC, equipped with a sound card and specially developed software has been proposed and its cost-effectiveness has been demonstrated. The system will for sure speed up the tedious work needed for the determination of the tinnitus frequencies and for the generation of the matching masking sound which is a time-consuming process for both the physician and the patient. A small clinical testing and experience proved that this time-consuming detection of pitch-frequency is much more shorter and simpler with this new software. This software, first of all, applies a simple audiometric test between 125-8000 Hz. The main stage in which the tinnitus frequency is detected, has an algorithm based on the Newton-Rhapson method. This process begins with the application of pure sinusoidal tone at 860 Hz that will change eventually according to the patient's trials to find the relieving sound for him. The scanning of tinnitus frequencies between 125 and 8000 Hz is repeated three times respectively. When this process is completed, a narrow-band white noise with a pure tone at the pitch frequency is synthesized. The software also includes a database for the personal information and the measurement data of the patients.

Browse

Browsing M.S. Theses by Title

Results Per Page

Sort Options