- Ankara, Ankara, Turkey
Ergin Atalar
Bilkent University, Electrical and Electronics Engineering, Faculty Member
Research Interests: Computer Science, Algorithms, Biomedical Engineering, Magnetic Resonance Imaging, Image Analysis, and 15 moreMedicine, Algorithm, Magnetic field, Catheterization, Humans, Feasibility Studies, Article, Head, Image Enhancement, Interventional MRI, Nuclear Magnetic Resonance Imaging, Equipment Design, Analytic Method, Catheter, and Electromagnetic coil
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Research Interests: Magnetic Resonance Imaging, Medicine, Catheterization, Chronic Disease, Animals, and 15 moreAnimal Model, Clinical Sciences, Angioplasty, Peripheral Vascular Disease, Perforation, Occlusion, Circulation, Carotid Artery, Interventional MRI, Equipment Design, Magnetic resonance image, Arterial Occlusive Diseases, Chronic total occlusion, Cardiovascular medicine and haematology, and Carotid artery diseases
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Research Interests: Magnetic Resonance Imaging, Nuclear medicine, Medicine, Biopsy, Human, and 15 moreHumans, Gold, Feasibility Studies, Male, Cancer Diagnosis, Hematuria, Article, Accuracy, Clinical Sciences, Cancer radiotherapy, Local Anesthesia, Nuclear Magnetic Resonance Imaging, Clinical Article, Equipment Design, and Magnetic resonance image
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Research Interests: Magnetic Resonance Imaging, Comparative Study, Medicine, Humans, Color, and 15 moreFemale, Blood, Male, Magnetic Resonance, Regression Analysis, Heart, Clinical Sciences, Image Enhancement, Observer Variation, Adult, Reproducibility of Results, Papillary Muscles, Mr Imaging, Heart Ventricles, and endocardium
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Figure 3: Selected three coronal images of the catheter phantom. a) Linear polarization mode with uncoupled case, b) forward polarization mode, c) reverse polarization mode. All three images are shown within the same gray-scale range... more
Figure 3: Selected three coronal images of the catheter phantom. a) Linear polarization mode with uncoupled case, b) forward polarization mode, c) reverse polarization mode. All three images are shown within the same gray-scale range Figure 1: Snapshot of client software (Interactive RF Polarization Control – IRPC), which controls the RF attributes of selected channels Interactive Real Time Inductively Coupled Catheter Coil Tracking Using a Transmit Array System Ugur Yilmaz, Li Pan, and Ergin Atalar Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, UMRAM, Bilkent University, Ankara, Turkey, Siemens Corporate Research, Center for Applied Medical Imaging, Baltimore, MD, United States
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Research Interests: Engineering, Computer Science, Acoustics, Computer Vision, Feasibility Study, and 15 moreComputer Simulation, Hybrid, Animals, Electromagnetic Induction, Fluorescence Imaging, Article, Controlled Study, Catheters, Calculation, Animal Experiment, Equipment Design, Amplitude Modulation, Catheter, Electromagnetic coil, and Excitation
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In magnetic particle imaging (MPI), simultaneous excitation and signal acquisition leads to direct feedthrough problems. While this direct-feedthrough can be mitigated up to some extent with passive compensation, this may not be... more
In magnetic particle imaging (MPI), simultaneous excitation and signal acquisition leads to direct feedthrough problems. While this direct-feedthrough can be mitigated up to some extent with passive compensation, this may not be sufficient given the time-variant nature of the system. Active compensation methods are proposed to overcome this challenge. In magnetic resonance imaging (MRI), we have recently proposed a promising active compensation technique that uses a vector modulator-like structure to modify a copy of the transmitted signal and use it for subtracting the direct-feedthrough in analog domain. In this work, this technique is adapted to MPI for active compensation of the direct-feedthrough. We demonstrate a significant increase in detection sensitivity at the fundamental harmonic on an in-house arbitrary waveform relaxometer. Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009065, DOI: 10.18416/IJMPI.2020.2009065
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PurposeTo dynamically minimize radiofrequency (RF)‐induced heating of an active catheter through an automatic change of the termination impedance.MethodsA prototype wireless module was designed that modifies the input impedance of an... more
PurposeTo dynamically minimize radiofrequency (RF)‐induced heating of an active catheter through an automatic change of the termination impedance.MethodsA prototype wireless module was designed that modifies the input impedance of an active catheter to keep the temperature rise during MRI below a threshold, ΔTmax. The wireless module (MR safety watchdog; MRsWD) measures the local temperature at the catheter tip using either a built‐in thermistor or external data from a fiber‐optical thermometer. It automatically changes the catheter input impedance until the temperature rise during MRI is minimized. If ΔTmax is exceeded, RF transmission is blocked by a feedback system.ResultsThe thermistor and fiber‐optical thermometer provided consistent temperature data in a phantom experiment. During MRI, the MRsWD was able to reduce the maximum temperature rise by 25% when operated in real‐time feedback mode.ConclusionThis study demonstrates the technical feasibility of an MRsWD as an alternativ...
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PurposeThe purpose of this study is to present a workflow for predicting the radiofrequency (RF) heating around the contacts of a deep brain stimulation (DBS) lead during an MRI scan.MethodsThe induced RF current on the DBS lead... more
PurposeThe purpose of this study is to present a workflow for predicting the radiofrequency (RF) heating around the contacts of a deep brain stimulation (DBS) lead during an MRI scan.MethodsThe induced RF current on the DBS lead accumulates electric charge on the metallic contacts, which may cause a high local specific absorption rate (SAR), and therefore, heating. The accumulated charge was modeled by imposing a voltage boundary condition on the contacts in a quasi‐static electromagnetic (EM) simulation allowing thermal simulations to be performed with the resulting SAR distributions. Estimating SAR and temperature increases from a lead in vivo through EM simulation is not practical given anatomic differences and variations in lead geometry. To overcome this limitation, a new parameter, transimpedance, was defined to characterize a given lead. By combining the transimpedance, which can be measured in a single calibration scan, along with MR‐based current measurements of the lead in...
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Research Interests: Biomedical Engineering, Magnetic Resonance Imaging, Image Analysis, Prostate Cancer, Medicine, and 15 moreDogs, Animals, Male, Dog, Prostate, Phased Array, Article, High Resolution, Magnetic, Phantom, Nonhuman, Nuclear Magnetic Resonance Imaging, Equipment Design, Cancer Staging, and Prostatic diseases
Research Interests: Computer Science, Biomedical Engineering, Magnetic Resonance Imaging, Catheterization, Animals, and 15 moreMagnetic Resonance, Decode and Forward, Article, Magnetics, Image Enhancement, Esophagus, Phantom, Nonhuman, Nuclear Magnetic Resonance Imaging, Equipment Design, Equipment Failure Analysis, In Vivo Study, Catheter, Inductive coupling, and Electromagnetic coil
Research Interests: Physics, Biomedical Engineering, Theory, MRI, Medicine, and 15 moreCatheterization, Dogs, Vascular Imaging, Animals, Antenna, Device, Article, Nonhuman, Guidewire, Nuclear Magnetic Resonance Imaging, Helical Antenna, Equipment Design, Insulation, Experimental Test, and Magnetic resonance angiography
Research Interests: Image Analysis, Catheterization, Feasibility Study, Female, Animals, and 15 moreFeasibility Studies, Fluoroscopy, Interventional Radiology, Article, Clinical Sciences, Animal Experiment, Equipment Design, D, Contrast Media, Contrast Enhancement, Balloon Catheter, Magnetic resonance angiography, Femoral Artery, Abdominal Aorta, and Aorta Abdominal
Research Interests: Engineering, Computer Science, Computer Vision, Magnetic Resonance Imaging, Feasibility Study, and 15 moreComputer Simulation, Hybrid, Animals, Electromagnetic Induction, Fluorescence Imaging, Article, Controlled Study, Catheters, Calculation, Interventional MRI, Animal Experiment, Equipment Design, Amplitude Modulation, Catheter, and Excitation
Research Interests: Computer Science, Materials Science, Thermography, Medicine, Magnetic Resonance Imaging (MRI), and 10 moreRadio Frequency, Scanner, Temperature measurement, Radiometry, Electrical Properties, Detector, Electrical And Electronic Engineering, Magnetic resonance image, microwave radiometry, and Depth of Penetration
Research Interests: Computer Science, Biomedical Engineering, Animals, Lead, Electromagnetic Induction, and 15 moreElectromagnetic Fields, Anura, Article, Electric Fields, Implant, Leg, Analytical Expressions, Electrode, Electric Field, Electrical And Electronic Engineering, Biomedical Equipment, Electric Potential, Active implants, Implantable Medical Devices, and Extremities
Background— Endovascular recanalization (guidewire traversal) of peripheral artery chronic total occlusion (CTO) can be challenging. X-ray angiography resolves CTO poorly. Virtually “blind” device advancement during x-ray–guided... more
Background— Endovascular recanalization (guidewire traversal) of peripheral artery chronic total occlusion (CTO) can be challenging. X-ray angiography resolves CTO poorly. Virtually “blind” device advancement during x-ray–guided interventions can lead to procedure failure, perforation, and hemorrhage. Alternatively, MRI may delineate the artery within the occluded segment to enhance procedural safety and success. We hypothesized that real-time MRI (rtMRI)–guided CTO recanalization can be accomplished in an animal model. Methods and Results— Carotid artery CTO was created by balloon injury in 19 lipid-overfed swine. After 6 to 8 weeks, 2 underwent direct necropsy analysis for histology, 3 underwent primary x-ray–guided CTO recanalization attempts, and the remaining 14 underwent rtMRI-guided recanalization attempts in a 1.5-T interventional MRI system. Real-time MRI intervention used custom CTO catheters and guidewires that incorporated MRI receiver antennae to enhance device visibili...
Research Interests: Magnetic Resonance Imaging, Medicine, Catheterization, Chronic Disease, Animals, and 15 moreAnimal Model, Clinical Sciences, Angioplasty, Peripheral Vascular Disease, Public health systems and services research, Perforation, Occlusion, Circulation, Carotid Artery, Interventional MRI, Equipment Design, Magnetic resonance image, Arterial Occlusive Diseases, Chronic total occlusion, and Cardiovascular medicine and haematology
Introduction MRI-guided biopsy procedures are becoming popular because of their excellent tissue contrast, multi-planar capabilities, and good vessel depiction. These procedures are performed with an MR-compatible needle in free-hand mode... more
Introduction MRI-guided biopsy procedures are becoming popular because of their excellent tissue contrast, multi-planar capabilities, and good vessel depiction. These procedures are performed with an MR-compatible needle in free-hand mode or in combination with a stereotactic ...
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In simultaneous transmission and reception (STAR) MRI, along with the coupling of the excitation pulse to the received signal, noise, and undesired distortions (spurs) coming from the transmit chain also leak into the acquired signal and... more
In simultaneous transmission and reception (STAR) MRI, along with the coupling of the excitation pulse to the received signal, noise, and undesired distortions (spurs) coming from the transmit chain also leak into the acquired signal and degrade image quality. Here, properties of this coupled noise and its relationship with the transmit amplifier gain, transmit chain noise density, isolation performance, and imaging bandwidth are analyzed. It is demonstrated that by utilizing a recently proposed STAR technique, the transmit noise can be reduced. The importance of achieving high isolation and careful selection of the corresponding parameters are demonstrated.
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The purpose of this study is to develop a wireless, flexible, ultra-thin, and passive radiofrequency-based MRI resonant fiducial marker, and to validate its feasibility in a phantom model and several body regions. Standard... more
The purpose of this study is to develop a wireless, flexible, ultra-thin, and passive radiofrequency-based MRI resonant fiducial marker, and to validate its feasibility in a phantom model and several body regions. Standard microfabrication processing was used to fabricate the resonant marker. The proposed marker consists of two metal traces in the shape of a square with an edge length of 8 mm, with upper and lower traces connected to each other by a metalized via. A 3T MRI fiducial marking procedure was tested in phantom and ex vivo, and then the marker's performance was evaluated in an MRI experiment using humans. The radiofrequency safety was also tested using temperature sensors in the proximity of the resonator. A flexible resonator with a thickness of 115 μm and a dimension of 8 × 8 mm was obtained. The experimental results in the phantom show that at low background flip angles (6-18°), the resonant marker enables precise and rapid visibility, with high marker-to-background...
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Multi-slice radiofrequency (RF) pulses have higher specific absorption rates, more peak RF power, and longer pulse durations than single-slice RF pulses. Gradient field design techniques using a z-gradient array are investigated for... more
Multi-slice radiofrequency (RF) pulses have higher specific absorption rates, more peak RF power, and longer pulse durations than single-slice RF pulses. Gradient field design techniques using a z-gradient array are investigated for exciting multiple slices with a single-band RF pulse. Two different field design methods are formulated to solve for the required current values of the gradient array elements for the given slice locations. The method requirements are specified, optimization problems are formulated for the minimum current norm and an analytical solution is provided. A 9-channel z-gradient coil array driven by independent, custom-designed gradient amplifiers is used to validate the theory. Performance measures such as normalized slice thickness error, gradient strength per unit norm current, power dissipation, and maximum amplitude of the magnetic field are provided for various slice locations and numbers of slices. Two and 3 slices are excited by a single-band RF pulse i...