Magnetik rezonans görüntüleme için orijinal RF bobin teknolojileri

ABSTRACTNOVEL RF COIL TECHNOLOGIES FORMRIHaydar ÇelikM.S. in Electrical and Electronics EngineeringSupervisor: Prof. Dr. Ergin AtalarJune, 2006In this thesis, we investigated five novel radiofrequency (RF) coiltechnologies for their use in Magnetic Resonance Imagers. These studies weregrouped into two: the first group was on RF coil technologies for interventionalMRI; the second group was on the design of optimally performing coils. As aresult of these studies, one journal paper was published, one other paper hadbeen submitted, and five abstracts were presented in international meetings.Interventional MRI is the technology that guides surgical procedures bythe aid of magnetic resonance images. One of the topics of interest ininterventional MRI is to determine the position of devices used during theinterventions. Recently, use of inductively coupled RF (ICRF) coils had beenproposed for this purpose. Our first group of studies was on development ofnovel technologies by using these ICRF coils. In the first study, we proposed amethod, which enables separate visualization of the ICRF coil in the body withone color-coded image by utilization of reverse and forward polarization modesof a receive-only (RO) birdcage coil. In the second study, we extended the firststudy by reformulating the ICRF coil visualization problem for phased arraycoils. With this, the proposed method became more practical since most of the4modern receive coils are phased array coils. In the third ICRF coil study, use ofICRF coil technology in image-guided neurosurgery was utilized as aregistration marker by increasing the signal intensity of gel markers.Our second group of studies started with calculation of the ultimateachievable signal-to-noise ratio (SNR) using any arbitrary internal coils. Thisultimate value later used to test the performance of various internal MRI coils.In the last study, we aimed to solve an inverse problem that is to design a coilthat generates SNR close to its ultimate value. First, we determined that abirdcage coil generates the optimum coil sensitivity; however, its z-directedsensitivity should be more localized in the center of the object. For this purpose,we designed and fabricated a microstrip based birdcage coil, which can be usedas head coil for 1.5 Tesla MR imagers.RF coils are critically important in performance of MRI scanners. Webelieve that studies conducted in this project are contributions toward obtainingbetter imaging systems.Key words: RF Coils, Endoluminal RF Coils, SNR in MRI, Interventional MRI;Catheter Tracking; Image guided surgery, Birdcage Coil, Microstrip Based RFCoils,5