Design and simulation of straight and tilted helical coils for magnetic resonance imaging

Abstract

In this thesis, helical coils are studied through Finite Element Method (FEM) analysis and fabrications are done as a part of the project of 5 Fr guiding catheter design for paediatric intracardiac procedures performed under Magnetic Resonance Imaging (MRI). The aim is to provide a reliable method to test the designed receiver coil structures without the need for fabrication. Straight and tilted helical coils are studied in details in order to bring out comparison between di erent models of helical coils which can be used for MRI applications. The mathematical expressions of these helices are pointed out and their magnetic ux densities are stated via dipole design methodology. FEM simulations are carried out for sample helical coils to make the computational analysis of their electrical and magnetic characteristics. After this, straight and tilted helical coils are fabricated having 10 mm and 5 mm diameter with changing winding numbers. These 26 fabricated coils are characterized via a vector network analyzer. The results are discussed to show the reliability of FEM simulations for their usage in catheter LC tip designs. Finally, a concept design and simulations of 1.5T MRI catheter device with double helical coils are performed using the same methodology, and the resonance frequency is found approximately as 63 MHz. The MRI test of a fabricated LC resonator circuit on catheter, which is carried out in parallel to this thesis study as a part of the overall project, is introduced in future works, aiming to combine FEM simulations and Micro Electro Mechanical Systems (MEMS) fabrication methods to produce optimized LC circuits for catheters.