Biyomedikal Mühendisliği Enstitüsü

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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.
3-D gamma knife distribution by normoxic gel dosimetry near tissue inhomogeneties
(Thesis (Ph.D.)-Bogazici University. Institute of Biomedical Engineering, 2005., 2005.) İşbakan, Fatih.; Ülgen, Yekta.
The primary goal in this study was to investigate the three dimensional dose distributions, near the areas of tissue inhomogeneities, in Gamma Knife Radiosurgery with the normoxic gel dosimetry. Following irradiation, when scanned in MR and post processing the MR images, dose imparted to any particular point in the gel phantom can be calculated via the true T2 relaxation time at that point. In the neighborhood of air-tissue inhomogeneity in the head, electronic disequilibrium can lead to errors in dose calculated with the treatment planning algorithms that presume the head as a homogeneous media. Two experiments were designed to investigate the inhomogeneity effects in the Gamma Knife radiosurgery: one experiment simulating the volume near the auditory canal cavity and, the other simulating the volume near the paranosal sinuses cavity. In the auditory canal cavity experiment, an identical balloon of a diameter of 16 cm with two corks placed on each side to represent the air cavities constitutes the inhomogeneous phantom. In the paranosal sinuses cavity experiment, a cylindrical cork is placed to represent the maximal sinuses. In both experiments, the homo geneous phantom is a spherical glass balloon filled with normoxic polymer gel. For dose calibrations, 100 ml vials filled with the same gel are irradiated at predefined doses, and the R2-dose calibration curve is extracted. Dose distributions are the results of a single shot, by using all 201 Cobalt sources, delivered to a known point in the phantoms. In the aspect of dosimetrical quality control, the Gamma Knife planning system predicted dose distribution is compared with the experimental results. In the homogeneous phantoms, the gel dosimetry calculated dose distribution is in good agreement with the GammaPlan predicted dose distribution. However, in the case of inhomogeneous phantoms, the dose distribution is spatially different and significant differences in dose levels are observed. The dose decrease near the air-tissue interface causes the overshooting of the dose by the GammaPlan. This underdosing effect can be essential for the lesions near tissue inhomogeneities. In the auditory canal cavity experiment, the diameter of the 50% isodose curves differ by 35% in the X axis and 1% in the Y axis for Z=105 mm axial plane; and by 39% in the X axis and 5% in the Z axis for Y=105 mm coronal plane in the inhomogeneous phantom as compared to the homogeneous phantom. In the paranosal sinuses cavity experiment, the diameter of the 50% isodose curves differ by 42% in the X axis and 47 %in the Y axis for Z=71mm axial plane; 42% in the X axis and 60%in the Y axis for Z=75 mm axial plane; 52% in the X axis and 70% in the Y axis for Z=79 mm axial plane respectively in the inhomogeneous phantom when compared to the homogeneous phantom. The dose decrease near the airtissue interface causes the Gamma Plan’s predicted dosage to be higher than that actually delivered. The resulting underdosing effect can be critical for the control of the lesions near tissue inhomogeneities.
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 hybrid biological/in silico neural network based brain-machine interface
(Thesis (Ph.D.)-Bogazici University. Institute of Biomedical Engineering, 2015., 2015.) Kocatürk, Mehmet.; Güveniş, Albert.; Gülçür, Halil Özcan.
Brain-machine interfaces (BMIs) aim to improve the lives of individuals with neurological disease or injury, by opening new information transfer channels between brain tissue and prosthetic actuators. In a majority of the BMI work, the data acquired from the motor cortex neurons are decoded into user's intended prosthetic actions by some "optimized" input-output mathematical model. Although this approach is quite sound, the information processing principles used are fundamentally di erent from those of natural neural circuits. In this thesis, we propose a novel, neurally-inspired design approach; the BMI controller consists of spiking model neurons and receives simulated synaptic inputs from extracellularly recorded neurons. The controller therefore forms a hybrid biological/in silico neural network with the neuronal circuits of the user's brain. In order to ful ll the challenging real-time requirements of the present design approach, we rst developed the Bioinspired Model Development Environment (BMDE). The BMDE, implemented on a hard real-time system, signi cantly facilitates BMI model development processes with powerful online data visualization tools while satisfying the strict timing constraints of the proposed design approach. Using the BMDE, we realized a novel, adaptive BMI controller which consists of in silico striatal medium spiny neurons, each receiving simulated synaptic inputs from extracellularly recorded motor cortex neurons. By implementing a reward-modulated spike timing-dependent plasticity rule and a winner-takes-all mechanism, the BMI controller, based on real-time closed-loop simulations, achieves perfect target reach accuracy for a two target reaching task in one dimensional space. Using this design approach and the BMDE, new generation BMI controllers that better mimic brain circuits can be developed. Moreover, by investigating the interactions between biological and in silico neural networks during neuroprosthetic control tryouts new neuroscienti c insights concerning motor control and learning can be obtained.
A macro-structural characteristic of brain white matter :|'dispersion' with its clinical and technical applications
(Thesis (Ph.D.)-Bogazici University. Institute of Biomedical Engineering, 2020., 2020.) Demir, Ali.; Özkan, Mehmed.
The main goal of this thesis is to find distinct macro-structural characteristics of brain white matter in the case of psychosis, where development of diagnostic imaging measures is necessary for early diagnosis and prospective studies. Given a tractogram data, which is a dense set of white matter fiber pathways of the whole brain obtained from diffusion magnetic resonance imaging, we propose to compute a global measure of dispersion for a voxel from the end point statistics of a set of fibers, which indicates complexity of the white matter voxel not locally but at macro scales. The findings on phantom data demonstrate sensitivity of the proposed measure to the tuning parameters and show its range characteristics. The findings on the real data demonstrate that proposed macro-structural dispersion information is found to be significant for discrimination of the schizophrenia and the bipolar patients from the healthy controls, especially when the frontally associative bundles such as cingulum and inferior occipito-frontal fasciculus are considered. The macroscopic dispersion measure is as informative as the local diffusion measures for the detection of changes in the white matter regions due to the psychosis. Beside, as a technical application, the dispersion map is considered and experimented for segmentation of cingulum. The findings of the thesis provide that the proposed measure is a potential diagnostic imaging marker in the case of psychosis and we contribute to the field of diagnostic research by generating a novel dispersion map of the brain that could be used for other clinical and technical applications.|Keywords : Brain white matter, macroscopic dispersion, tractogram, bipolar, schizophrenia.
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 model of active and attentive vision
(Thesis (Ph.D.) - Bogazici University. Institute of Biomedical Engineering, 2002., 2002.) Soyer, Çağatay.; Bozma, H. Işıl.
Biological vision systems explore their environment by allocating their resources to interesting parts of a scene, using both physical and mental attention mechanisms. The result of this active and attentive vision behavior is a sequence of images obtained from different spatial locations at different times. However, temporal processes and integration mechanisms in the brain enable us to interpret this information and perceive a stable image of the environment. While models of such attention and perception mechanisms are invaluable to understand human vision, they are also increasingly used and improved by robotics and artificial intelligence researchers to achieve human-like performance. In a similar attempt, we propose a new and complete model of active vision behavior, based on confirmed biological evidence where available. The model consists of an attention system, temporal image sequence processing algorithms and an integrative visual memory. All components of the model are implemented on our mobile robot APES. Gaze control, sequence based scene recognition and visual integration tasks are assumed during experiments. Results of gaze control experiments clearly demonstrate a human-like selective attention behavior, which can be fully controlled by a number of parameters. In recognition and integration tasks, simple and complex scenes were successfully modeled and classified. Furthermore, our work on attentional image sequences raised a number of interesting questions, some of which have been answered in this thesis.
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 neurovascular coupling model based on nitric oxide and carbon dioxide and its validation with two-photon microscopy imaging
(Thesis (Ph.D.)-Bogazici University. Institute of Biomedical Engineering, 2010., 2010.) Yücel, Meryem Ayşe.; Akın, Ata.
Understanding neurovascular coupling is of paramount importance since while a normal coupling is vital for a healthy functioning brain, the impairment in coupling is the underlying factor of many neurodegenerative diseases. With this motivation, we aimed to test the still-debatable hypotheses and important aspects of neurovascular coupling: whether the coupling is controlled metabolically or neurogenically, how the coupling is propagated, what kinetics the cerebral metabolic rate of oxygen (CMRO2) follows during neuronal activity and the transient characteristics of the response during stimulus and after stimulus periods. We have modi ed recent models of neurovascular coupling adding the e ects of both nitric oxide (NO) kinetics, a well-known neurogenic vasodilator, and CO2 kinetics as a metabolic vasodilator to test the neurogenic and metabolic hypotheses. Using 2-photon microscopy imaging, we measured the vessel diameter changes in vivo in somatosensory cortex of Sprague Dawley rats during forepaw stimulation to investigate response transients and to test retrograde dilation hypothesis. Our results show that the dominant factor in the hemodynamic response is NO, however CO2 is important in modulating the shape of the response: causing poststimulus undershoot due to the washout e ect of cerebral blood ow (CBF) resulting in hypocapnia. The statistical analysis of our experimental results and their comparison with the modeling results give more insight into the transient characteristics of the response. Our results support retrograde dilation hypothesis and suggests a CMRO2 onset and return kinetics in seconds rather than in minutes during functional activity.|Keywords: Neurovascular coupling, Neurogenic hypothesis, Metabolic hypothesis, Nitric oxide, Carbon dioxide, 2-photon microscopy.
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.

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