M.S. Theses
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Item Predicting kidney tumor subtype from CT images using radiomics and clinical features(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2022., 2022) Şirin, Duygu.; Güveniş, Albert.This study aims to evaluate the performance of machine learning methods in predicting the subtype (clear-cell vs. non-clear- cell) of kidney tumors using clinical patient and radiomics data from CT images. CT images of 192 malignant kidney tumor cases (142 clear-cell, 50 other) from TCIA’s KiTS-19 Challenge were used in the study. There were several different tumor subtypes in the other group, most of them being chromophobe or papillary RCC. Patient clinical data were combined with the radiomic features extracted from CT images. Features were extracted from 3D images and all of the slices were included in the feature extraction process. Initial dataset consisted of 1157 features of which 1130 were radiomics and 27 were clinical. Features were selected using Kruskal Wallis - ANOVA test followed by Lasso Regression. After feature selection, 8 radiomic features remained. None of the clinical features were considered important for our model as a result. Training set classes were balanced using SMOTE. Training data with the selected features were used to train the Coarse Gaussian SVM and Subspace Discriminant classifiers. Coarse Gaussian SVM was faster compared to Subspace Discriminant with a training time of 0.47 sec and 11000 obs/sec prediction speed. Training duration of Subspace Discriminant was 4.1 sec with 960 obs/sec prediction speed. For Coarse Gaussian SVM was found as 0.86 while for Subspace Discriminant AUC was 0.85. Both models produced promising results on classifying malignant tumors as ccRCC or non-ccRCC. NOTE Keywords : Kidney Tumor, Clear-Cell, Machine Learning, CT Imaging.Item Assessment of effectiveness of muscle lengthening surgery in cerebral palsy using musculoskeletal modeling(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2022., 2022) Biricik, Eda.; Yücesoy, Can A.Cerebral Palsy is a permanent movement disorder that manifests itself at early childhood, as poor coordination, and gait difficulty due to muscle spasticity and/or con tracture. Excessive knee flexion during gait e.g., crouch gait is a common impairment and often corrected by hamstring lengthening surgery. Such crouch gait is presumed to originate from shortness (i.e., contracture) and/or slowness in lengthening (i.e., spastic ity) of affected muscles and remedial surgery is considered to improve gait by increasing muscle length or its velocity. However, a third group of patients who neither has short nor slow hamstrings pre-operatively can still undergo surgery. The aim of the thesis is to investigate whether the gait of those patients improved after the surgery by testing the hypotheses: post-operatively, (i) the knee joint movement is improved (ii), the hip joint movement is deteriorated (iii), the gait deviation index (GDI) is increased (iv), muscle unit length do not change, and (v) pre-operative psoas muscle lengths were shorter. Findings showed that mean knee angle decreased significantly at the initial contact (0-3%), terminal stance (28-43%), and the terminal swing phases (95-100%) (p< 0.05). No significant effects were detected in the hip angle or the GDI. Additionally, no significant changes in the hamstring muscle lengths were found. Only half of the patients had shorter psoas muscle lengths pre-operatively. In conclusion, the excessive knee flexion of the patients was decreased without negatively affecting hip movement or gait overall. The improvement in the knee angle was achieved without any change in the muscle length of the hamstrings, suggesting that an isometric position shift of the target muscle occurs, which may be ascribed to post-surgical alterations in the epimuscular connections. NOTE Keywords : Hamstring lengthening surgery, Remedial surgery, Spasticity, Contrac ture, OpenSim, Musculoskeletal modeling, Psoas, Lengthening velocity, Muscle short ness, Cerebral Palsy.Item Proof-of-principle of ed-DBS (Experien-driven deep brain stimulation) in the hemiparkinson rat model(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2022., 2022) Tamer, Betül.; Schulz, Daniel.Parkinson’s Disease (PD) is a neurodegenerative disease characterized by the progressive loss of dopamine (DA) neurons in the substantia nigra (SN). The loss of DA leads to debilitating motor symptoms, such as tremors, rigidity, and bradykinesia. Deep brain stimulation (DBS) is considered state- of-the-art in the treatment of motor symp toms in advanced PD. The standard practice is to stimulate the subthalamic nucleus (STN) or internal globus pallidus (GPi) continuously via surgically implanted elec trodes. However, continuous administration of DBS conflicts with the firing patterns of nigrostriatal DA neurons because these neurons generate rapid phasic DAergic sig nals in response to specific experiences, such as the presentation of a reward-predicting stimulus (S) or an unexpected reward (S*). This conflict may be one of the reasons for only moderate treatment efficacy of DBS. In our Boğazici University Scientific Research Projects (BAP) project, we hypothesize that treatment outcomes are enhanced if DBS is given acutely, in an experience dependent (ed) fashion that is tailored to specific ex periences of the subject, involving S -S* contingencies (Experience-driven (ed)-DBS to improve motor symptoms in the hemiparkinson rat model under grant number 15981). Towards a test of this hypothesis, we will a) integrate DBS with operant conditioning in which experiences can be completely controlled, and b) determine the value of ed DBS for the brain. In this thesis, we took initial steps towards achieving these aims. Specifically, we integrated the operant setup with DBS and tested the viability of our methods with two rats, one hemiparkinson rat and one control. In this thesis work, we report data which show support for the success of our behavioral training procedures, surgical approach, and integration of a conditioned inhibition procedure with ed-DBS. NOTE Keywords : Variable Interval Schedule, Discrimination Learning, Hemiparkinson Rat, 6-Hydroxydopamine, Apomorphine-Induced Rotation.Item Spatiotemporal graph convolutional neural networks for motor imagery EEG classification(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2022., 2022) Alramly, Ahmed Mohamed Mohamed Mohamed.; Ademoğlu, Ahmet.Electroencephalography (EEG) has various applications in medicine, neuro-science, and neural engineering. It records the electrical activity of the brain tissues caused by the interaction among different neuronal communities. Numerous algorithms for the automatic classification of EEG signals have been developed. These algorithms work via extracting unique and non-redundant features from EEG signals. However, the majority of the proposed algorithms employ temporal components of EEG signals while disregarding the rich spatial network structure that underlies in the EEG. In this study, we propose a classification pipeline that uses the network structure of EEG data for a simultaneous representation of spatial and temporal features in the EEG signals. First, graph theory is utilized to model the EEG networks in two spatial domains; i) the sensor space and ii) the cortical source space. Second, a spatiotem- poral graph convolutional neural network (STGCNN) classification model is employed combining both temporal and spatial features of EEG data for its classification under motor imagery conditions. Additionally, the model is tested using the cortical source space data in each of the seven resting state brain networks individually to estimate their performance on classification accuracy. The results show that STGCNN model performs slightly better than the temporal convolutional neural network (CNN) models by 1.25%. NOTE Keywords : EEG, Spatiotemporal Graph Convolutional Neural Networks, Brain Networks.Item Investigating the bacterial adhesion behaviour on bone surface mimicked chitosan membranes(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2022., 2022) Uçak, Meltem.; Garipcan, Bora.; İyisan, Banu.An extremely serious post-op consequence of orthopedic replacement surgery is infection, which is currently challenging to treat with antibiotics. According to data, prosthesis infections correlate with biofilm formation that is highly resilient to host immune defenses and antibiotics. The main goal of this thesis is to examine the re lationship between topography and surface-cell and surface-bacteria interactions. The secondary objective is to determine whether it is possible to chemically alter potential implant surfaces and their topographical features to maximize cell-implant interactions while minimizing bacterial-implant interactions. Physicochemical characterization for Graphene Oxide (GO) coated bone surface mimicked Chitosan (BSM-CH-GOc) loaded Ampicillin sodium salt (Amp) or Tetracycline hydrochloride (Tetra) membranes were done via degradation test, Scanning Electron Microscopy (SEM) and drug release study. For cell study, mouse fibroblast (L929) was selected as a model mammalian cell line. Bacterial behavior on these membranes was investigated using the biofilm growth test. The rate of biofilm production was assessed and utilized as an indication in which Es cherichia Coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538) were utilized as model organisms. It was found that while GO coated bone surface mimicked chitosan membranes had a noticeable effect on preventing bacterial biofilm formation, the pres ence of ampicillin sodium salt and tetracycline hydrochloride remarkably reduced the biofilm formation compared to the control groups. NOTE Keywords : Surface-cell interactions, Surface-bacteria interactions, Chitosan, Ampi cillin, Tetracycline.Item Effects of hamstring lengthening surgery on muscle-tendon velocities of patients with cerebral palsy(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2022., 2022) Turan, Fatma.; Yücesoy, Can A.Cerebral Palsy (CP) is a permanent movement disorder seen in early child hood, consisting of muscle spasticity and/or contracture, and difficulty in walking due to poor selective control. In CP patients, crouch gait with excessive knee flexion is usually corrected by hamstring lengthening surgery, which is believed to improve gait, by increasing the length or velocity of the spastic muscle. However, hamstring mus cles that may not be not short and slow before the surgery can also be operated on. The thesis aims to assess whether the gait of CP patients improved after the surgery by testing the following hypotheses: (i) knee joint movement does not improve post surgery, (ii) the hip joint movement was impaired pre -surgery, (iii) the gait deviation index (GDI) increases post- surgery, (iv) the muscle lenghtening velocity remains un changed in postsurgery, and (v) the pre-surgery psoas lenghtening velocity is slower than post-surgery. 8 limbs of 4 CP patients who had undergone hamstring lengthening surgery were included in the study. Pre-and post-surgery muscle lengthening veloc ity changes of patients were compared with reference to age-matched TD children (14 limbs of 7 participants) based on gait analysis data and using musculoskeletal modeling (OpenSim). Our results showed that post-surgery, mean knee angular velocity did not change significantly. No significant effect of surgery was shown in hip angular velocity or GDI. Moreover, no significant changes were shown in hamstring muscle lenghtening velocities. Only two of the preoperative patients had slow psoas muscle lenghtening ve locity. As a result, post-surgery improvement in knee movement was achieved without a significant change in hamstring muscle lenghtening velocity. NOTE Keywords : Muscle Shortness, Cerebral Palsy, Contracture, OpenSim, Hamstring Lengthening Surgery, Spasticity, Psoas, Lengthening Velocity.Item Evaluation of local oxygen consumption in human flexor digitorum suoerficialis muscle by near infrared spectroscopy(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Erdoğan, Sinem Burcu.; Akın, Ata.A strong relationship between mechanical and physiological conditions of skele- tal muscle determines the force generated by that muscle. The aim of this study was to evaluate the relationship between local oxygen consumption and local force produced during isometric contractions at varying biomechanical conditions. Another aim of the study was to investigate the e ect of relative position and absolute length changes on local energy consumption of exor digitorum super cialis (FDS) muscle during isomet- ric contractions performed at various muscle length and force levels. Nine healthy male subjects performed sustained isometric handgrip exercise by continuously pressing on a hand dynamometer. The handgrip exercise was performed while the wrist is (i) maximally exed, (ii) maximally extended and (iii) in neutral position. Local oxygen consumption (mVO2) and time course of recovery (trec) of FDS muscle were measured by functional near infrared spectroscopy (fNIRS). mVO2 and trec were linearly related with force level up to 40% of maximal voluntary contraction force (MVC) at all wrist positions (p<0.05). At each force level, mVO2 was observed to be lowest when the wrist was maximally extended (p=0.0004). Both parameters presented a decrease as the wrist was extended. The results imply that local energy consumption has a dependence on muscle relative position and length. It is suggested that myotendinious force transmission between a muscle and its surrounding structures might be a determinant of local of energy consumption.|Keywords: Near infrared spectroscopy, local oxygen consumption, isometric handgrip exercise.Item The effect of methylphenidate on brain hemodynamics of attention-deficit/hyperactivity disorder measured by functional near infrared spectroscopy(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Topaloğlu, Nermin.; Akın, Ata.Attention-deficit/hyperactivity disorder (ADHD) is a very common neurodevelopmental disorder. Approximately 30% 60% of individuals diagnosed with ADHD in youth have symptoms that persist into adulthood. This neurobehavioral disorder results in significant functional impairment. It decreases the life quality of the patients. Therefore, the need for recognition and treatment of patients with ADHD is necessary. Methylphenidate (MPH) is known to reduce hyperactivity in individuals with ADHD. Yet little is known about how it alters neural activity and how this relates to its clinical effects. Functional Near-Infrared Spectroscopy (fNIRS) is a portable, non-invasive brain imaging method measuring the changes in oxygenated hemoglobin [HbO2] and deoxyhemoglobin [HbH] levels particularly in prefrontal cortex. In this study, 15 adult, right handed cases with DSM-IV diagnosis of Attention deficit hyperactivity disorder (ADHD) were evaluated with fNIRS during a cognitive task which is Stroop test. The goal of this study is to examine MPH-induced hemodynamic changes during a cognitive activity, and to examine how these changes correlate with measures of behavioral response to the drug during Stroop task. It is found that MPH effectively decreased HbO levels. The reason of the decreased level of HbO after medication is vasoconstriction. MPH normalized the behavior during an executive function test. MPH has a great effect on the response time of the subjects to NS, CS, and IS. MPH always shortens the durations of the reaction times.|Keywords: Functional Near-Infrared Spectroscopy, Attention-Deficit/Hyperactivity Disorder (ADHD), Methylphenidate, Stroop task, adult.Item Magnitude estimation by the non-pacinian I tactile channel(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Dinçer, Şeref Mete.; Güçlü, Burak.Psychophysical responses to mechanical stimuli were measured to study the sense of touch. By using a forward-masking procedure on eight subjects, magnitude estimation was performed by activating the Non-Pacinian I tactile channel. For each subject, 40-Hz and 250-Hz absolute thresholds were found. Additionally, the 250-Hz masking stimuli that were required to mask the Pacinian channel for selectively activating the Non- Pacinian I channel were determined. The masking stimuli were applied before the test stimuli to find the masked thresholds at 40 Hz. In the final set of experiments, suprathreshold stimuli were used to find magnitude estimation values. These values fit power functions well. Experimental results were compared to neural simulated population responses to study the origins of the power law. The model simulations that used the total number of spikes as the intensity code predicted the experimental results better.|Keywords: somatosensory, mechanoreceptor, power law, masking, Meissner corpusclesItem Building a measurement setup for the investigation of acoustic cavitations for medical applications(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Erdem, Şener.; Güçlü, Burak.Various noninvasive medical treatments rely on high intensity ultrasound or shock waves. The externally generated pressure waves transfer a large amount of energy into the body. There is evidence that in all of these treatments cavitation provides the main contribution to the desired effects. Cavitation consists of the formation and violent collapse of gas bubbles with sudden gas release. Examples of medical treatments where cavitation plays an important role are the destruction of urinary calculi by application of extracorporeal shock waves, the noninvasive ablation of tumors, localized drug delivery, and improved drug uptake by tissues. Unfortunately, the energy transfer during cavitation is often poorly controlled, frequently leading to inefficient treatment, hemorrhage, and undesired cell damage. In this study a setup is designed, built and tested to investigate microbubble cavitation and its possible effects on kidney stone destruction in combination with high intensity focused ultrasound (HIFU). Optical cavitation detection is monitored during ultrasound excitation by means of a digital camera. Active and passive cavitation detection techniques are used to detect cavitation events. Micro bubbles with different shell types and size distributions are tested. Artificial kidney stones are tested to see whether the HIFU transducer is able to damage a kidney stone. Preliminary results do not show, however, a significant influence of microbubble infusion on kidney stone destruction by means of HIFU.|Keywords: Ultrasound; cavitation; microbubbles; lithotripsy; HIFUItem Design of the biomedical calibration laboratory quality manual for EN 17025: 2005(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Doğu, Hande.; Ülgen, Yekta.According to the New Approach Directives, the CE Marking is obligatory for medical products: the manufacturer affixes this marking in order to be allowed to sell his product in the European market. CE marked devices can only be tested and controlled by accredited laboratories. It is the aim of this project to design the laboratory quality manual in compliance with the EN 17025 standard, for the Biomedical Calibration Laboratory of Boğaziçi University. By searching other related international standards, minimum documentation requirements are determined: besides a draft Laboratory Quality Manual, draft documents such as policies, procedures and instructions are prepared within the scope of this master thesis. In the Appendices, a simple strategy plan on how to implement the EN 17025 standard in BME Biomedical Calibration Laboratory is also presented.|Keywords: Laboratory Quality Manual, Accreditation, CE Mark, Biomedical EquipmentItem Design of a wide range kVp-meter(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Tümer, Murat.; Ülgen, Yekta.The kVp setting is one of the major factors affecting the image quality in X-ray imaging and should be annually measured and calibrated if necessary. In this thesis, a kVp-meter is designed and a prototype unit was built and the performance was tested in terms of accuracy and reliability. The design is based on the dependency of the attenuation coefficient of metals on the energy of the incident photons, which is related to kVp. The tests on the prototype showed that the accuracy and precision are both below 1% in the diagnostic range. As the same measuring principle applies for mammography unit, this device can be also used for kVp measurements of mammography units. The accuracy and precision in the mammography mode are below 1%, too.|Keywords: Kilovolts peak, X-ray, photodiode, copper filter, linear attenuation coefficient, calibration.Item Design of a Wi-Fi based electrocardiography monitoring system(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Kocatürk, Mehmet.; Özkan, Mehmed.The objective of this project is to design a wireless ECG monitoring system which enables the tracking of ambulatory patients' cardiac activities on a central server. A developed software run on a server and the client devices on patients yield providing support for nearly real-time traceability of patient ECG data. The software on the server, which is technically able to handle unlimited numbers of connections of client devices, appropriately communicates with the remote devices and provides plotting of electrocardiogram of a selected patient who is preregistered with the software. The client device, carried by the patient, includes an ECG ampli er circuit which also includes necessary lters to avoid undesired signals, and manages analog to digital conversion of ampli ed ECG signal as well as its transmission to the server. IEEE 802.11b, as the wireless communication protocol, opted and involved in this design for ensuring data transmission between client devices on patients and the server, has rapidly penetrated in applications in Machine to Machine (M2M) communicating product lines except medical ones. What is more, due to rapid penetration of 802.11x (Wi-Fi) which simpli es the adaptation of the client devices developed with this study to the currently established networks, the designed system, in the aim of wireless ECG monitoring, can be foreseen to supply high e ciency in the further products of several ECG monitoring applications.|Keywords: ECG, Wi-Fi, IEEE 802.11, Telemedicine.Item Investigating lipid signaling in rat hippocampal slices with patch-clamp tight seal whole cell recording technique(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Genç, Özgür.; Saybaşılı, Hale.Ceramide, besides its structural role in cell membrane as a sphingolipid, has essential roles in apoptosis, cell growth and di erentiation. In this study, the e ect of C2-ceramide (10 μM) application on whole cell currents recorded by patch-clamp technique from cell body of hippocampal CA1 pyramidal neurons was investigated. Evoked post-synaptic currents were recorded with low frequency (0.1 Hz) stimulation of Scha er collateral. It was observed that ceramide application resulted with depression among the NMDA currents. On the other hand, there was not any signi cant in uence on non-NMDA currents. The role of C2-ceramide which leads to the depression on the NMDA currents showed that sphingolipids have an e ect directly on the cell membrane, besides their roles as secondary messengers inside the cell.|Keywords: C2-ceramide, hippocampal synaptic currents, NMDA and non-NMDA currents, patch-clamp tight seal whole cell technique.Item Bayesian EEG source reconstruction using Markov chain Monte Carlo methods(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Yıldız, Gökçen.; Ademoğlu, Ahmet.Item Robust design of breast scintigraphy collimator using Monte Carlo Simulations and response surface methodology(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Balta, Sinem.; Güveniş, Albert.Breast Scintigraphy, a nuclear medicine breast imaging technique, is a supplemental breast exam that is used in patients to investigate a breast abnormality. It is not a primary investigative tool for breast cancer but it is used as a complementary technique in cases where conventional x-ray mammography has some limitations in breast cancer diagnosis. However, studies show that breast scintigraphy does not give successful results when breast abnormality is less than 1cm. The collimator plays an important role in image construction. This study aims to make a robust design of the breast scintigraphy system collimator to obtain a better image quality in small breast lesions (<1cm) by the optimization of the collimator parameters such as hole length (collimator length), hole size and septal thickness while keeping the lesion detectability less susceptible to patient variations such as breast and lesion dimensions. The breast and the lesion were modeled as a cylinder and a sphere, respectively. Monte Carlo Simulation is utilized for simulating the imaging system and Response Surface Methodology is applied for robust optimization. The first part of the study deals with a typical case of breast and lesion dimensions whereas the second part inserts variance to the parameters. Our results show that a hole length of 1.74cm, a hole size of 0.14cm and a septal thickness of 0.02cm are the dimensions of a robust collimator.|Keywords: Breast Scintigraphy, collimator, Monte Carlo Simulation, Response Surface Method, robust designItem Design and instrumentation of a coronary care unit(Thesis (M.S.) - Bogazici University. Institute of Biomedical Engineering, 1985., 1985.) Kireçyan, Ari.; Istefanopulos, Yorgo.In this study, the main principles that must be obeyed in the design and equipment selection of a coronary care unit are investigated along with the architectural steps which could be used in the establishment of such a unit. Information is given about the bedside monitors, central console monitors and other assisting devices which must be present in an optimal coronary care unit (CCU). The operation principles of these devices are explained by means of block diagrams. The computerized forms of these units which are widespread in developed countries and their advantages are also explained. The characteristics that the hospital's electrical network must have in order for the desired CCU to be realized and the precautions to ensure patient, user and visitor safety are described. The coronary care unit in the Etfal Hospital, the Cerrahpasa, a Hospital, the Haydarpaşa Gogus Cerrahisi Hospital and in the Medical University of Istanbul Çapa Hospital which are functioning in Istanbul are investigated. Information is given about the existing design and some suggestions to solve the problems that arise are offered. In short, the major purpose of this thesis is to built up a source of information on how to realize a CCU design at optimal usefullness and efficiency, taking the economy and technical conditions of the country into consideration.Item Evaluation of the continuous detector concept for PET systems dedicated to small animals by using the Monte Carlo simulation method(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2007., 2007.) Ertürk, Sakine Şebnem.; Güveniş, Albert.A detector design especially for small animal PET systems requires taking into account three main factors: these are high energy and spatial resolution and price. When examining the state-of-the-art PET detectors, it can be seen that many researchers have preferred to use continuous (monolithic), block or discrete crystals for small animal PET systems. Although, the discrete crystal detector designs have provided high spatial resolution, they also have caused many complications such as, reduced light collection (low packing fraction), labour-intensive use and increased costs. In this study, to overcome these limitations, the feasibility of using a continuous crystal instead of block or discrete designs has been explored for high resolution small animal PET applications. For this aim, a PET detector for small animals based on continuous block Lutetium oxyorthosilicate crystal (LSO) (16mm x 16mm) coupled to a PS-PMT (Hamamatsu H8711-03) has been designed. When working with continuous crystals, surface treatment and crystal thickness are important factors that strongly determine the main characteristics of the detector module. Therefore, for the development of this explored small animal PET detector, the effects of these factors on the detector module performances have been investigated, in order to optimize crystal configuration. In this study 4 different surface treatments (Polish + Black, Ground + Black, Ground + Methacrylate, Ground + Air), 3 different crystal thickness (3mm-6mm-9mm) and 41 different source coordinates were used. The obtained results for the energy resolution, spatial resolution and image compression have been presented when using different surface treatments and thicknesses in continuous LSO crystals. The simulation results have been carried out by using DETECT2000 package. The end word, high spatial resolution is the most important parameter for a PET detector. In our study, Ground + Air (GA) surface treatment gives the highest special resolution but, the image compression is poor. However, this poorness can be avoided by using certain statistics based positioning (SBP) algorithms.Item Design and implementation of an ECG based emergency telediagnostic system(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2006., 2006.) Dilber, Baran.; Ademoğlu, Ahmet.This thesis aims for the design and implementation of a software system for distributed emergency diagnosis to be used in conjunction with ambulatory electrocardiography (ECG/EKG) devices. The software consists of a Digital Signal Processor (DSP) helper library for processing and conditioning the ECG signals, a database for central data storage, and an expert user interface for ECG data evaluation. The system primarily aims to reduce the gap between patients and experts (cardiologists) and allows for the rapid diagnosis of acute myocardial infarction (AMI), commonly known as heart attack. This will consequently decrease the time span between the onset of symptoms and treatment. However, this system can also be used for the diagnosis of other forms of cardiovascular diseases, as well as a means of routine monitoring of cardiac patients.|Keywords: Telemedicine, ECG/EKG, telecardiology, electrophysiology, AMI, MI, pre-hospital thrombolysis.Item Design of an embedded communication framework for an amergency telecardiology system(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2006., 2006.) Yıldırım, Onur.; Ademoğlu, Ahmet.Acute myocardial infarction (AMI or MI) occurs whwn a part of the heart muscle dies because of sudden total interruption of blood flow to that area. Itis a life-threatening medical emergency which demands immediate activation of the emergency medical services. This thesis proposes the development of an embedded communication framework designed to enable quick diagnosis of AMI and immediate activation of emergency medical services targeted to it. The system consists of an embedded communication software along with a TCP/IP based sever software for a GSM based ambulatory ECG device. Both, the software components running on the ECG device and the communication server enable the device to be remotely interfaced by the call center software and controlled by the cardiologists.|Keywords: Mobile ECG device, AMI, Pre-hospital thrombolysis, 12-lead ECG over GSM