title: Dry phantom for magnetoencephalography -Configuration, calibration, and contribution.
abstract: BACKGROUND
  An artificial object that imitates human brain activity is called "phantom" and is used for evaluation of magnetoencephalography (MEG) systems. The accuracy of the phantom itself had not been guaranteed in the previous studies, although role of the phantom is to evaluate the accuracy of MEG measurement. The purposes of this paper are to develop a novel MEG phantom that can be calibrated and to demonstrate the advantages of the calibrated phantoms.
  
  
  METHODS
  We proposed and fabricated a practical dry phantom that is composed of 50 isosceles-triangle coils based on Ilmoniemi's model. This phantom was calibrated based on three-dimensional measurement of the current paths in the phantom and on numerical calculations.
  
  
  RESULTS
  The calibrated positions of the equivalent current dipoles (ECDs) shifted 0.83mm, on average, from the designed positions. The uncertainties of the calibrated ECDs were also evaluated, by combining the uncertainties which could reasonably be attributed to them.
  
  
  CONCLUSIONS
  Furthermore, we demonstrated performance of the developed phantom through experimental evaluation of an MEG system. The results of this evaluation differed from those obtained using an uncalibrated phantom. Moreover, the calibrated phantom can provide detailed information regarding the uncertainty of the measurement and also the uncertainty of the phantom itself.
  
  
  CONCLUSIONS
  A more appropriate evaluation of MEG measurements can be achieved using a calibrated phantom.
authors.affiliation: Applied Electronics Laboratory, Kanazawa Institute of Technology, 3 Amaike, Kanazawa, Ishikawa 920-1331, Japan. Electronic address: oyama@neptune.kanazawa-it.ac.jp.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Oyama
authors.affiliation: Applied Electronics Laboratory, Kanazawa Institute of Technology, 3 Amaike, Kanazawa, Ishikawa 920-1331, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Adachi
authors.affiliation: Department of Clinical Laboratory, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Ishikawa 113-8655, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Yumoto
authors.affiliation: Applied Electronics Laboratory, Kanazawa Institute of Technology, 3 Amaike, Kanazawa, Ishikawa 920-1331, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Hashimoto
authors.affiliation: Applied Electronics Laboratory, Kanazawa Institute of Technology, 3 Amaike, Kanazawa, Ishikawa 920-1331, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Uehara
mesh_terms: D000465:Algorithms; D002138:Calibration; D006801:Humans; D021621:Imaging, Three-Dimensional; D015225:Magnetoencephalography; D008962:Models, Theoretical; D019047:Phantoms, Imaging
keywords: Calibration; Magnetoencephalography; Measurement uncertainty; Phantom