title: Evidence for spleen-specific uptake of a microbubble contrast agent: a quantitative study in healthy volunteers.
abstract: OBJECTIVE
  To evaluate the pharmacokinetics of the microbubble contrast agent BR1.
  
  
  METHODS
  Twenty healthy volunteers were injected via arm vein with a 1.2-mL bolus of BR1. Ultrasonographic images of liver and right kidney and of spleen and left kidney were obtained intermittently for 5 minutes with low-mechanical-index software (to minimize microbubble destruction) that shows stationary microbubbles in green. Percentage total uptake was calculated as the number of green pixels in the region of interest for each organ over time, divided by the total pixels. Relative uptake, the ratio of total uptake in liver to that in right kidney and of total uptake in spleen to that in left kidney, and differential uptake, the difference in total uptake between liver and right kidney and between spleen and left kidney, were calculated. Total uptake for each organ was plotted against time, and the gradient of a best-fit straight line was calculated. Wilcoxon signed rank test was used to compare mean uptake values in each subject. Mann-Whitney U test was used for comparisons in sex and age.
  
  
  RESULTS
  Total uptake declined over 5 minutes in left and right kidney and in liver (from 88% +/- 10% [1 minute] to 67% +/- 14% [5 minutes]), but not in spleen (range, 90%-99%). Mean relative uptake +/- 1 SD for spleen increased from 2.3 +/- 0.7 (1 minute) to 3.7 +/- 2.3 (5 minutes) (P =.005) but for liver was constant: 2.1 +/- 0.9 (1 minute) and 2.3 +/- 0.4 (5 minutes) (P =.06). Mean differential uptake +/- 1 SD for spleen increased from 51.3% +/- 14.9% (1 minute) to 65.0% +/- 9.1% (5 minutes) (P =.002). Significant difference was seen over time in total uptake gradients between spleen and left kidney (P =.014) but not between liver and right kidney or right and left kidney. No difference was seen between men and women or with age.
  
  
  CONCLUSIONS
  BR1 produces spleen-specific enhancement that is longer (5 minutes) than the blood pool phase.
authors.affiliation: Imaging Sciences Department, MRC Clinical Sciences Centre, Imperial College London, Hammersmith Hospital, DuCane Rd, London W12 0HS, England, UK. a.lim@imperial.ac.uk
authors.forename: Adrian K P
authors.initials: AK
authors.lastname: Lim
authors.forename: Nayna
authors.initials: N
authors.lastname: Patel
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Eckersley
authors.forename: Simon D
authors.initials: SD
authors.lastname: Taylor-Robinson
authors.forename: David O
authors.initials: DO
authors.lastname: Cosgrove
authors.forename: Martin J K
authors.initials: MJ
authors.lastname: Blomley
mesh_terms: D000328:Adult; D003287:Contrast Media; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging; D008099:Liver / Q000000981:diagnostic imaging; D008297:Male; D045423:Microbubbles; D008875:Middle Aged; D010743:Phospholipids; D012016:Reference Values; D013154:Spleen / Q000000981:diagnostic imaging*; D013459:Sulfur Hexafluoride; D014463:Ultrasonography
chemical_list: D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride