title: Particle swarm optimization for programming deep brain stimulation arrays.
abstract: Deep brain stimulation (DBS) therapy relies on both precise neurosurgical targeting and systematic optimization of stimulation settings to achieve beneficial clinical outcomes. One recent advance to improve targeting is the development of DBS arrays (DBSAs) with electrodes segmented both along and around the DBS lead. However, increasing the number of independent electrodes creates the logistical challenge of optimizing stimulation parameters efficiently.
  
  
  
  Solving such complex problems with multiple solutions and objectives is well known to occur in biology, in which complex collective behaviors emerge out of swarms of individual organisms engaged in learning through social interactions. Here, we developed a particle swarm optimization (PSO) algorithm to program DBSAs using a swarm of individual particles representing electrode configurations and stimulation amplitudes. Using a finite element model of motor thalamic DBS, we demonstrate how the PSO algorithm can efficiently optimize a multi-objective function that maximizes predictions of axonal activation in regions of interest (ROI, cerebellar-receiving area of motor thalamus), minimizes predictions of axonal activation in regions of avoidance (ROA, somatosensory thalamus), and minimizes power consumption.
  
  
  
  The algorithm solved the multi-objective problem by producing a Pareto front. ROI and ROA activation predictions were consistent across swarms (<1% median discrepancy in axon activation). The algorithm was able to accommodate for (1) lead displacement (1 mm) with relatively small ROI (⩽9.2%) and ROA (⩽1%) activation changes, irrespective of shift direction; (2) reduction in maximum per-electrode current (by 50% and 80%) with ROI activation decreasing by 5.6% and 16%, respectively; and (3) disabling electrodes (n  =  3 and 12) with ROI activation reduction by 1.8% and 14%, respectively. Additionally, comparison between PSO predictions and multi-compartment axon model simulations showed discrepancies of  <1% between approaches.
  
  
  
  The PSO algorithm provides a computationally efficient way to program DBS systems especially those with higher electrode counts.
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Edgar
authors.initials: E
authors.lastname: Peña
authors.forename: Simeng
authors.initials: S
authors.lastname: Zhang
authors.forename: Steve
authors.initials: S
authors.lastname: Deyo
authors.forename: YiZi
authors.initials: Y
authors.lastname: Xiao
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Johnson
mesh_terms: D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D046690:Deep Brain Stimulation / Q000295:instrumentation* / Q000379:methods*; D004567:Electrodes, Implanted; D020342:Finite Element Analysis; D008253:Macaca mulatta; D046228:Microarray Analysis / Q000295:instrumentation* / Q000379:methods*; D008959:Models, Neurological; D013788:Thalamus / Q000502:physiology*; D013813:Therapy, Computer-Assisted / Q000379:methods*