title: Modified perturbation method for transverse electromagnetic (TEM) coil tuning and evaluation.
abstract: A modified perturbation method for tuning and testing volume head coils was developed. The common perturbation method, utilizing the change in resonance frequency of a resonator in response to the presence of a small dielectric or magnetic probe, was modified to modulate the frequency shift due to rotation of a probe. This modification enabled the RF magnetic and electric fields as well as the angular distribution of current in the longitudinal elements of the coil to be mapped. The latter serves as a quick test of magnetic field homogeneity by comparing the measured distribution with the sinusoidal function required for the field to be homogenous. The method was experimentally applied to tune and test a transverse electromagnetic (TEM) head coil.
authors.affiliation: Department of Radiology, Albert Einstein College of Medicine, Bronx, New York 10461, USA. navdievi@aecom.yu.edu
authors.forename: Nikolai I
authors.initials: NI
authors.lastname: Avdievich
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Krymov
authors.forename: Hoby P
authors.initials: HP
authors.lastname: Hetherington
mesh_terms: D000465:Algorithms; D002138:Calibration; D004574:Electromagnetic Fields; D019544:Equipment Failure Analysis / Q000379:methods*; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods* / Q000592:standards; D011786:Quality Control; D011874:Radiometry / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity