title: Dynamic bioluminescence imaging for quantitative tumour burden assessment using IV or IP administration of D: -luciferin: effect on intensity, time kinetics and repeatability of photon emission.
abstract: BACKGROUND
  In vivo bioluminescence imaging (BLI) is a promising technique for non-invasive tumour imaging. D: -luciferin can be administrated intraperitonealy or intravenously. This will influence its availability and, therefore, the bioluminescent signal. The aim of this study is to compare the repeatability of BLI measurement after IV versus IP administration of D: -luciferin and assess the correlation between photon emission and histological cell count both in vitro and in vivo.
  
  
  METHODS
  Fluc-positive R1M cells were subcutaneously inoculated in nu/nu mice. Dynamic BLI was performed after IV or IP administration of D: -luciferin. Maximal photon emission (PE(max)) was calculated. For repeatability assessment, every acquisition was repeated after 4 h and analysed using Bland-Altman method. A second group of animals was serially imaged, alternating IV and IP administration up to 21 days. When mice were killed, PE(max) after IV administration was correlated with histological cell number.
  
  
  RESULTS
  The coefficients of repeatability were 80.2% (IV) versus 95.0% (IP). Time-to-peak is shorter, and its variance lower for IV (p < 0.0001). PE(max) was 5.6 times higher for IV. A trend was observed towards lower photon emission per cell in larger tumours.
  
  
  CONCLUSIONS
  IV administration offers better repeatability and better sensitivity when compared to IP. In larger tumours, multiple factors may contribute to underestimation of tumour burden. It might, therefore, be beneficial to test novel therapeutics on small tumours to enable an accurate evaluation of tumour burden.
authors.affiliation: In Vivo Cellular and Molecular Imaging (ICMI) Laboratory, Vrije Universiteit Brussel (VUB), Brussels, Belgium. Marleen.Keyaerts@vub.ac.be
authors.forename: Marleen
authors.initials: M
authors.lastname: Keyaerts
authors.forename: Jacob
authors.initials: J
authors.lastname: Verschueren
authors.forename: Tomas J
authors.initials: TJ
authors.lastname: Bos
authors.forename: Lea Olive
authors.initials: LO
authors.lastname: Tchouate-Gainkam
authors.forename: Cindy
authors.initials: C
authors.lastname: Peleman
authors.forename: Karine
authors.initials: K
authors.lastname: Breckpot
authors.forename: Chris
authors.initials: C
authors.lastname: Vanhove
authors.forename: Vicky
authors.initials: V
authors.lastname: Caveliers
authors.forename: Axel
authors.initials: A
authors.lastname: Bossuyt
authors.forename: Tony
authors.initials: T
authors.lastname: Lahoutte
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000008:administration & dosage; D049454:Firefly Luciferin / Q000008:administration & dosage*; D007274:Injections, Intraperitoneal; D007275:Injections, Intravenous; D007700:Kinetics; D008027:Light; D008163:Luminescent Measurements / Q000379:methods*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D012208:Rhabdomyosarcoma / Q000473:pathology*
chemical_list: D003287:Contrast Media; D049454:Firefly Luciferin