title: Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy.
abstract: This study aims at a systematic assessment of five computational models of a birdcage coil for magnetic resonance imaging (MRI) with respect to accuracy and computational cost.
  
  
  
  The models were implemented using the same geometrical model and numerical algorithm, but different driving methods (i.e., coil "defeaturing"). The defeatured models were labeled as: specific (S2), generic (G32, G16), and hybrid (H16, [Formula: see text]). The accuracy of the models was evaluated using the "symmetric mean absolute percentage error" ("SMAPE"), by comparison with measurements in terms of frequency response, as well as electric ( ||→E||) and magnetic ( || →B ||) field magnitude.
  
  
  
  All the models computed the || →B || within 35% of the measurements, only the S2, G32, and H16 were able to accurately model the ||→E|| inside the phantom with a maximum SMAPE of 16%. Outside the phantom, only the S2 showed a SMAPE lower than 11%.
  
  
  
  Results showed that assessing the accuracy of || →B || based only on comparison along the central longitudinal line of the coil can be misleading. Generic or hybrid coils - when properly modeling the currents along the rings/rungs - were sufficient to accurately reproduce the fields inside a phantom while a specific model was needed to accurately model ||→E|| in the space between coil and phantom.
  
  
  
  Computational modeling of birdcage body coils is extensively used in the evaluation of radiofrequency-induced heating during MRI. Experimental validation of numerical models is needed to determine if a model is an accurate representation of a physical coil.
authors.affiliation: Sapienza University of Rome, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Lucano
authors.affiliation: Sapienza University of Rome.
authors.forename: Micaela
authors.initials: M
authors.lastname: Liberti
authors.affiliation: Office of Science and Engineering Laboratories, U.S. FDA, CDRH.
authors.forename: Gonzalo G
authors.initials: GG
authors.lastname: Mendoza
authors.affiliation: Imricor Medical Systems, Burnsville, MN, USA.
authors.forename: Tom
authors.initials: T
authors.lastname: Lloyd
authors.affiliation: Office of Science and Engineering Laboratories, U.S. FDA, CDRH.
authors.forename: Maria Ida
authors.initials: MI
authors.lastname: Iacono
authors.affiliation: Sapienza University of Rome.
authors.forename: Francesca
authors.initials: F
authors.lastname: Apollonio
authors.affiliation: Imricor Medical Systems, Burnsville, MN, USA.
authors.forename: Steve
authors.initials: S
authors.lastname: Wedan
authors.affiliation: Office of Science and Engineering Laboratories, U.S. FDA, CDRH.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kainz
authors.affiliation: Office of Science and Engineering Laboratories, U.S. FDA, CDRH, Silver Spring, MD, USA.
authors.forename: Leonardo M
authors.initials: LM
authors.lastname: Angelone
mesh_terms: D003198:Computer Simulation; D004574:Electromagnetic Fields; D004867:Equipment Design; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D019047:Phantoms, Imaging; D011846:Radio Waves; D015203:Reproducibility of Results