title: Quantitative phase contrast images to quantitate flow in a rat model of microgravity.
abstract: A magnetic resonance angiographic (MRA) technique for noninvasive measurement of flow in the inferior vena cava (IVC) was used to study blood flow changes in a simulated microgravity model. Microgravity was simulated in adult male Fischer 344 rats (n = 12, with each rat acting as its own control) using a tail harness to elevate the hindquarters, producing a non-weight bearing hindlimb (NWH) model. Quantitative phase contrast images of flow within the IVC were obtained initially and after a 2-week NWH protocol. Inferior vena cava blood flow was determined by converting the intensity at the respective magnetic resonance pixels into a corresponding flow by Doppler techniques. Average values for flow determined with MR angiography were 351.8 (SEM = 49) mm3 x s(-1) initially and 524.5 (SEM = 46) mm3 x s(-1) after exposure to 2 weeks of the NWH protocol. Post 2-week NWH flow increased 49.1% over the initial NWH value. Using a paired t-test, a significant difference was found between the rats' IVC flow values in the initial and post-NWH groups (p < 0.004). The changes in IVC blood flow due to 45 degrees NWH may contribute to the overall changes observed in the cardiovascular system during simulated microgravity.
authors: Department of Pediatrics, University of Arizona Health Sciences Center, Tucson 85724-0001, USA.
authors: A M
authors: AM
authors: Hays
authors: R L
authors: RL
authors: Keller
authors: A F
authors: AF
authors: Gmitro
authors: M I
authors: MI
authors: Alpbach
authors: K R
authors: KR
authors: Sridhar
authors: M P
authors: MP
authors: Balagtas
authors: M L
authors: ML
authors: Witten
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D018810:Magnetic Resonance Angiography; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D014682:Vena Cava, Inferior / Q000502:physiology*; D014893:Weightlessness