Design and Development of a Planar B0-Coil for Patient Respiratory Motion Correction in Magnetic Resonance Imaging

We detail the design, construction, and testing of a planar B0-coil which will ultimately be used to reduce artifacts in magnetic resonance imaging (MRI) caused by respiratory motion in patients. The B0-coil combined with a micro-electro-mechanical system microcoil detector mounted on a catheter and deployed in an endoscope should in-principle enable sub-millimeter resolution MR imaging of cholangiocarcinomas. The B0-coil has been designed to generate around 300 uT of magnetic field, parallel to the main field of a MRI scanner, and to be homogenous to around 1% in a 150 mm diameter of spherical volume (DSV). Measurements of the field in the DSV reveal that there are no field gradients present (within our experimental resolution of 3 uT) in the region and the field is homogeneous with a mean value of 324.5 ± 4.3 uT (1σ) at 25 A. The B0-coil was subsequently deployed in MRI experiments on a test phantom to confirm axial and sagittal image slice shifts of 12 and 3 mm, respectively, using only 5.5 A in the B0-coil. This clearly demonstrates the principle of image slice shifting by modulating the main field of a MRI magnet using a relatively small field generated in an insert coil.