Design of biplanar gradient coils for magnetic resonance imaging of the human torso and limbs

• Published in: Magnetic resonance imaging Vol. 17; no. 5; pp. 739 - 754
• Main Authors: Williams, G.B., Fisher, B.J., Huang, C.L-H, Carpenter, T.A., Hall, L.D.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.06.1999; Elsevier Science
• Subjects: Algorithms; Biological and medical sciences; Equipment Design; Genetic algorithm; Gradient coil; Humans; Image correction; Image Enhancement; Investigative techniques, diagnostic techniques (general aspects); Magnetic Resonance Imaging - instrumentation; Magnetics; Medical sciences; Models, Genetic; Models, Theoretical; Osteoarticular system. Muscles; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Surface Properties; Gradient coil; Genetic algorithm; Image correction; Human; Image processing; Limb; Diseases of the osteoarticular system; Error correction; Superposition; Technique; Magnetic field; Nuclear magnetic resonance imaging; Optimization; Coil
• ISSN: 0730-725X; 1873-5894
• DOI: 10.1016/S0730-725X(99)00012-0

A method is described for design of gradient coils of unconventional geometry for MRI that is based on the superpositions of magnetic fields arising from individual current elements calculated by the Biot-Savart Law. Use of an optimization method based on a genetic algorithm enables a wide diversity in the shapes of coil that can be modeled. To exemplify this a two axis, biplanar gradient set is presented; this geometry offers good access for rectangular objects whilst holding the coils closer to the region of interest than is possible for cylindrical configurations. The inner dimensions of the gradient set were 40.0 × 24.4 × 40.0 cm and the gradient efficiencies were 0.3 and 0.4 mT m −1 A −1 in the z- and y- directions respectively over a 15 cm diameter region. Correction of signals arising from regions for which gradient linearity was not optimized was successful for the monotonic region within the set; the largest cuboid from which the MR signal could be processed to produce an undistorted image is of dimensions 36.3 × 17.2 × 24.4 cm.