title: Use of intravoxel incoherent motion MR imaging to assess placental perfusion in a murine model of placental insufficiency.
abstract: OBJECTIVE
  The objectives of this study were to evaluate the potential of intravoxel incoherent motion (IVIM) magnetic resonance imaging at 4.7 T to distinguish decreased placental perfusion from normal perfusion in a controlled murine model and to determine the effect of transient maternal hyperoxygenation on placental microvascularization.
  
  
  METHODS
  The study was approved by our animal care committee. Ten pregnant rats underwent ligation of the left uterine vascular pedicle on the 17th embryonic day (E17). A multishot diffusion-weighted spin-echo echo-planar imaging sequence, using 14 b values (b10 to b800), was performed on the 19th embryonic day (E19) under room air and during maternal hyperoxygenation. For each placenta and its 2 layers, the signal intensity decay curve according to the b values was obtained. The following IVIM parameters were calculated using biexponential fitting: the diffusion coefficient (D), the pseudodiffusion coefficient (D*), and the perfusion fraction (f). Mixed regression modeling was used to analyze the effect of ligation status, oxygenation, and the placental layer on IVIM parameters.
  
  
  RESULTS
  Seventy-three placentas were examined: 23 in the ligated horn and 50 in the nonligated control horn. The IVIM parameters were obtained for 67% of the placentas. In the control horn, the mean (SD) values on room air were 28% (13%), 9.6 (9) ×10(-3) mm(2)/s, and 0.88 (0.36) ×10(-3) mm(2)/s for the perfusion fraction, the pseudodiffusion coefficient, and the diffusion coefficient, respectively. The perfusion fraction was significantly decreased in the ligated horn (-6.7% [1.9%]; P = 0.001) and during maternal hyperoxygenation (-3.3 [1.64%]; P = 0.047). The diffusion coefficient increased significantly during the hyperoxygenation (0.26 [0.04] × 10(-3) mm(2)/s; P = 0.0001) and in the inner placental layer (0.21 [0.05] ×10(-3) mm(2)/s; P = 0.0001).
  
  
  CONCLUSIONS
  The perfusion fraction is a sensitive marker of decreased placental perfusion. The perfusion fraction and the diffusion coefficient are modified during the hyperoxygenation. Our IVIM-based approach may help in the investigation and early diagnosis of vascular diseases during pregnancy.
authors.affiliation: INSERM, UMR, Paris Cardiovascular Research Center, Université Paris Descartes, Sorbonne Paris Cité, France. marianne.alison@rdb.aphp.fr
authors.forename: Marianne
authors.initials: M
authors.lastname: Alison
authors.forename: Gihad E
authors.initials: GE
authors.lastname: Chalouhi
authors.forename: Gwennhael
authors.initials: G
authors.lastname: Autret
authors.forename: Daniel
authors.initials: D
authors.lastname: Balvay
authors.forename: Rokhaya
authors.initials: R
authors.lastname: Thiam
authors.forename: Laurent J
authors.initials: LJ
authors.lastname: Salomon
authors.forename: Charles André
authors.initials: CA
authors.lastname: Cuenod
authors.forename: Olivier
authors.initials: O
authors.lastname: Clement
authors.forename: Nathalie
authors.initials: N
authors.lastname: Siauve
mesh_terms: D000818:Animals; D017352:Echo-Planar Imaging; D005260:Female; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D010920:Placenta / Q000098:blood supply*; D010927:Placental Insufficiency / Q000503:physiopathology*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley