title: Magnetic cell delivery for peripheral arterial disease: A theoretical framework.
abstract: OBJECTIVE
  Our aim was to compare different magnet arrangements for magnetic cell delivery to human lower leg arteries and investigate the theoretical targeting efficiency under realistic flow conditions as a possible treatment after angioplasty. Additionally the potential of scaling down or translating the magnetic actuation device for preclinical studies was explored.
  
  
  METHODS
  Using finite element methods, the magnetic field distribution was calculated in 3D for the optimization of magnet arrangements. Computational fluid dynamics simulations were performed for the human posterior tibial artery with the geometry and boundary condition data derived from magnetic resonance imaging (MRI) studies. These simulations were used to trace the trajectories of cells for an optimized magnet arrangement. Additionally the behavior of cells close to the vessel wall was investigated using a fluid-structure interaction model.
  
  
  RESULTS
  The optimal magnet for the lower leg arteries was a Halbach cylinder k3 variety (12 elements with 900 rotation steps for the magnetization orientation). With this magnet, numerical simulations predict a targeting efficiency of 6.25% could be achieved in the posterior tibial artery for cells containing 150 pg iron. Similar simulations, which were scaled down to rabbit dimensions while keeping the forces acting on a cell constant, lead to similar predicted targeting efficiencies. Fluid dynamic and fluid-structure interaction simulations predict that magnetically labeled cells within a 0.5% radii distance to the vessel wall would be attracted and remain at the wall under physiological flow conditions.
  
  
  CONCLUSIONS
  First pass capture of magnetically labeled cells under pulsatile flow conditions in human lower leg arteries leads to low targeting efficiencies. However, this can be increased to almost 100% by stopping the blood flow for 5 min. A magnetic actuation device can be designed for animal models that generate magnetic forces achievable for cells in human leg arteries.
authors.affiliation: Centre for Advanced Biomedical Imaging, Department of Medicine and Institute of Child Health, University College London, London WCIE 6DD, United Kingdom. j.riegler@ucl.ac.uk
authors.forename: Johannes
authors.initials: J
authors.lastname: Riegler
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Lau
authors.forename: Ana
authors.initials: A
authors.lastname: Garcia-Prieto
authors.forename: Anthony N
authors.initials: AN
authors.lastname: Price
authors.forename: Toby
authors.initials: T
authors.lastname: Richards
authors.forename: Quentin A
authors.initials: QA
authors.lastname: Pankhurst
authors.forename: Mark F
authors.initials: MF
authors.lastname: Lythgoe
mesh_terms: D000818:Animals; D017690:Cell Transplantation / Q000379:methods*; D002478:Cells, Cultured; D003198:Computer Simulation; D004574:Electromagnetic Fields; D042783:Endothelial Cells / Q000502:physiology / Q000528:radiation effects* / Q000637:transplantation*; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008280:Magnetics / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D058729:Peripheral Arterial Disease / Q000503:physiopathology* / Q000601:surgery*; D011817:Rabbits