title: Supraceliac and Infrarenal Aortic Flow in Patients with Abdominal Aortic Aneurysms: Mean Flows, Waveforms, and Allometric Scaling Relationships.
abstract: OBJECTIVE
  Hemodynamic forces are thought to play a critical role in abdominal aortic aneurysm (AAA) growth.In silicoandin vitrosimulations can be used to study these forces, but require accurate aortic geometries and boundary conditions. Many AAA simulations use patient-specific geometries, but utilize inlet boundary conditions taken from a single, unrelated, healthy young adult.
  
  
  METHODS
  In this study, we imaged 43 AAA patients using a 1.5 T MR scanner. A 24-frame cardiac-gated one-component phase-contrast magnetic resonance imaging sequence was used to measure volumetric flow at the supraceliac (SC) and infrarenal (IR) aorta, where flow information is typically needed for simulation. For the first 36 patients, individual waveforms were interpolated to a 12-mode Fourier curve, peak-aligned, and averaged. Allometric scaling equations were derived from log-log plots of mean SC and IR flow vs. body mass, height, body surface area (BSA), and fat-free body mass. The data from the last seven patients were used to validate our model.
  
  
  RESULTS
  Both the SC and IR averaged waveforms had the biphasic shapes characteristic of older adults, and mean SC and IR flows over the cardiac cycle were 51.2 ± 10.3 and 17.5 ± 5.44 mL/s, respectively. Linear regression of the log-log plots revealed that BSA was most strongly predictive of mean SC (R2= 0.29) and IR flow (R2= 0.19), with the highest combinedR2. When averaged, the measured and predicted waveforms for the last seven patients agreed well.
  
  
  CONCLUSIONS
  We present a method to estimate SC and IR mean flows and waveforms for AAA simulation.
authors: Department of Bioengineering, Stanford University, Stanford, CA, USA.
authors: Andrea S
authors: AS
authors: Les
authors: Janice J
authors: JJ
authors: Yeung
authors: Geoffrey M
authors: GM
authors: Schultz
authors: Robert J
authors: RJ
authors: Herfkens
authors: Ronald L
authors: RL
authors: Dalman
authors: Charles A
authors: CA
authors: Taylor
keywords: Biphasic waveform; Body surface area (BSA); Linear regression; Phase-contrast magnetic resonance imaging (PC-MRI); Weight