Electromagnetic Simulation of Signal Distribution of Various RF Endoluminal Loop Geometries with Coil Orientation: Towards a Reconfigurable Design

• Published in: Concepts in magnetic resonance. Part B, Magnetic resonance engineering Vol. 2021; pp. 1 - 15
• Main Authors: Raki, Hamza, Tse Ve Koon, Kevin, Souchay, Henri, Robb, Fraser, Beuf, Olivier
• Format: Journal Article
• Language: English
• Published: Hindawi 28.07.2021; John Wiley & Sons, Inc; Wiley
• Subjects: Computer Science; Electromagnetism; Electronics; Engineering Sciences; Medical Imaging; Microelectromechanical systems
• ISSN: 1552-5031; 1552-504X
• DOI: 10.1155/2021/6614696

With the objective of improving MR endoluminal imaging of the colonic wall, electromagnetic simulations of different configurations of single-layer and double-layer, and double-turn endoluminal coil geometries were run. Indeed, during colon navigation, variations in coil orientation with respect to B0 are bound to occur, leading to impaired image acquisition due to a loss of signal uniformity. In this work, three typical coil orientations encountered during navigation were chosen and the resulting signal uniformity of the different geometries was investigated through the simulated B1x,y/IRt values. Sampling this quantity over a circle of radius r enabled us to calculate the coefficient of variation (= standard deviation/mean) for this given distance. This procedure was repeated for r∈5;15  mm, which represents the region of interest in the colon. Our results show that single-loop and double-layer geometries could provide complementary solutions for improved signal uniformity. Finally, using four microelectromechanical system switches, we proposed the design of a reconfigurable endoluminal coil able to switch between those two geometries while also ensuring the active decoupling of the endoluminal coil during the RF transmission of an MR experiment.