title: Frameless multimodal image guidance of localized convection-enhanced delivery of therapeutics in the brain.
abstract: BACKGROUND
  Convection-enhanced delivery (CED) has been shown to be an effective method of administering macromolecular compounds into the brain that are unable to cross the blood-brain barrier. Because the administration is highly localized, accurate cannula placement by minimally invasive surgery is an important requisite. This paper reports on the use of an angiographic c-arm system which enables truly frameless multimodal image guidance during CED surgery.
  
  
  METHODS
  A microcannula was placed into the striatum of five sheep under real-time fluoroscopic guidance using imaging data previously acquired by cone beam computed tomography (CBCT) and MRI, enabling three-dimensional navigation. After introduction of the cannula, high resolution CBCT was performed and registered with MRI to confirm the position of the cannula tip and to make adjustments as necessary. Adeno-associated viral vector-10, designed to deliver small-hairpin micro RNA (shRNAmir), was mixed with 2.0 mM gadolinium (Gd) and infused at a rate of 3 μl/min for a total of 100 μl. Upon completion, the animals were transferred to an MR scanner to assess the approximate distribution by measuring the volume of spread of Gd.
  
  
  RESULTS
  The cannula was successfully introduced under multimodal image guidance. High resolution CBCT enabled validation of the cannula position and Gd-enhanced MRI after CED confirmed localized administration of the therapy.
  
  
  CONCLUSIONS
  A microcannula for CED was introduced into the striatum of five sheep under multimodal image guidance. The non-alloy 300 μm diameter cannula tip was well visualized using CBCT, enabling confirmation of the position of the end of the tip in the area of interest.
authors.affiliation: Department of Radiology, University of Massachusetts, Worcester, Massachusetts 01655, USA.
authors.forename: Imramsjah M J
authors.initials: IM
authors.lastname: van der Bom
authors.forename: Richard P
authors.initials: RP
authors.lastname: Moser
authors.forename: Guanping
authors.initials: G
authors.lastname: Gao
authors.forename: Miguel
authors.initials: M
authors.lastname: Sena-Esteves
authors.forename: Neil
authors.initials: N
authors.lastname: Aronin
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Gounis
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism; D001921:Brain / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism*; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation / Q000379:methods*; D018481:Convection; D000229:Dependovirus / Q000378:metabolism; D016503:Drug Delivery Systems / Q000295:instrumentation / Q000379:methods*; D005471:Fluoroscopy / Q000295:instrumentation / Q000379:methods; D005682:Gadolinium / Q000008:administration & dosage / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D038361:Neuronavigation / Q000295:instrumentation / Q000379:methods*; D012756:Sheep
chemical_list: D005682:Gadolinium