title: Optimisation of current injection protocol based on a region of interest.
abstract: OBJECTIVE
  Electrical impedance tomography has the potential to image fast neural activity associated with physiological or epileptic activity throughout the brain. These applications pose a particular challenge as expected voltage changes on the electrodes are less than 1% and geometrical constraints of the body under investigation mean that electrodes can not be evenly distributed around its boundary. Unlike other applications, however, information regarding the location of expected activity is typically available. An informative method for choosing current paths that maximise sensitivity to specific regions is desirable.
  
  
  METHODS
  Two electrode addressing protocol generation methods based on current density vectors concentrated in a region of interest have been proposed. One focuses solely on maximising its magnitude while the other considers its distribution. The quality of reconstructed images using these protocols was assessed in a simulation study conducted in a human and rat mesh and compared to the protocol that maximises distance between injecting electrodes.
  
  
  RESULTS
  When implementing the protocol that focused on maximising magnitude, the current density concentrated in a region of interest increased by up to a factor of 3. When the distribution of the current was maximised, the spread of current density vectors increased by up to fivefold. For the small conductivity changes expected in the applications explored, image quality was best when implementing the protocol that maximised current density. The average image error when using this protocol was 7% better than when employing other protocols.
  
  
  CONCLUSIONS
  We conclude that for fast neural EIT applications, the protocol that maximises current density is the best protocol to implement.
authors.forename: Mayo
authors.initials: M
authors.lastname: Faulkner
authors.forename: Markus
authors.initials: M
authors.lastname: Jehl
authors.forename: Kirill
authors.initials: K
authors.lastname: Aristovich
authors.forename: James
authors.initials: J
authors.lastname: Avery
authors.forename: Anna
authors.initials: A
authors.lastname: Witkowska-Wrobel
authors.forename: David
authors.initials: D
authors.lastname: Holder
mesh_terms: D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging*; D017097:Electric Impedance; D004566:Electrodes; D004827:Epilepsy / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional; D051381:Rats; D014054:Tomography / Q000295:instrumentation / Q000379:methods*