title: Jeannette Wilkins Award: Can locally delivered gadolinium be visualized on MRI? A pilot study.
abstract: BACKGROUND
  Management of orthopaedic infections relies on débridement and local delivery of antimicrobials; however, the distribution and concentration of locally delivered antimicrobials in postdébridement surgical sites is unknown. Gadolinium-DTPA (Gd-DTPA) has been proposed as an imaging surrogate for antimicrobials because it is similar in size and diffusion coefficient to gentamicin.
  
  
  OBJECTIVE
  Is in vivo distribution of locally delivered Gd-DTPA (1) visible on MRI; (2) reliably visualized by different observers; (3) affected by the anatomic delivery site; and (4) affected by the in vitro release rate from the delivery vehicle?
  
  
  METHODS
  Twenty-four local delivery depots were imaged in nine rabbits using two anatomic sites (intramedullary canal, quadriceps) with Gd-DTPA in intermediate-porosity polymethylmethacrylate (PMMA) or high-porosity PMMA; six of the nine rabbits also had Gd-DTPA delivered in collagen at a third site (hamstring). A total of 45,000 fat-suppressed T1-weighted RARE scans were acquired using a 7-T Bruker Biospec MRI: nine rabbits, 2-mm slices over 10 cm, four TR values, 25 time periods (pre, every 15 minutes for 6 hours). T1 maps were constructed at every time period. Gd-DTPA distribution was observed qualitatively on the T1 maps. Interobserver reliability was determined.
  
  
  RESULTS
  Locally delivered Gd-DTPA was visible. Interobserver agreement was excellent. Intramuscular delivery followed intermuscular planes; intramedullary delivery was contained within the canal by bone. Distribution from collagen decreased after 1 hour but from PMMA increased over 6 hours.
  
  
  CONCLUSIONS
  Locally delivered Gd-DTPA can be visualized on MRI; distribution is affected by anatomical location and delivery vehicle.
  
  
  CONCLUSIONS
  Contrast-based imaging using locally delivered Gd-DTPA may be useful as an antibiotic surrogate to determine antibiotic distribution in surgical sites.
authors.affiliation: Center for Interventional Biomaterials, School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, USA.
authors.forename: Morgan B
authors.initials: MB
authors.lastname: Giers
authors.forename: Chris S
authors.initials: CS
authors.lastname: Estes
authors.forename: Alex C
authors.initials: AC
authors.lastname: McLaren
authors.forename: Michael R
authors.initials: MR
authors.lastname: Caplan
authors.forename: Ryan
authors.initials: R
authors.lastname: McLemore
mesh_terms: D000818:Animals; D001363:Awards and Prizes; D003287:Contrast Media / Q000008:administration & dosage*; D019786:Gadolinium DTPA / Q000008:administration & dosage*; D008279:Magnetic Resonance Imaging; D010865:Pilot Projects; D011817:Rabbits
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA