Signal-to-noise improvement in mid-field MRI surface coils: A degree in plumbing?

✍ Scribed by P.M. Walker; B. Robin-Lherbier; J.M. Escanyé; J. Robert

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 482 KB
• Volume: 9
• Category: Article
• ISSN: 0730-725X
• DOI: 10.1016/0730-725x(91)90537-v

✦ Synopsis

From a series of standard SE imaging sequences, performed on a Bruker 0.28 T imaging system, with the assistance of a healthy volunteer, the image signal-to-noise (S/N) ratio obtained from a 23-cm square surface coil has been shown to increase by up to 38% as the tube gauge is increased from 4 to 18 mm. The reason did not lie solely in the much improved Q factor of the unloaded coils. Despite a more than twofold increase in the unloaded Q factor, the loaded coil Q values only increased by 8%. It would appear, however, that the resistive, dielectric and inductive noise components are all reduced, and hence contribute to the observed improved S/N. The reduction in pure ohmic losses accounts for a quarter of the improved S/N, while the reduced inductive and dielectric losses provide the remaining three quarters. No independent quantification of the two latter noise sources was attempted, although a reduced dielectric contribution is confirmed qualitatively by a reduction in the negative frequency shift of the resonance frequency as a function of increasing coil gauge when the coil is loaded.