title: Normalizing fractional moving blood volume estimates with power Doppler US: defining a stable intravascular point with the cumulative power distribution function.
abstract: OBJECTIVE
  To normalize the power Doppler ultrasound (US) signal to the expected signal from 100% blood in the calculation of a fractional moving blood volume estimate.
  
  
  METHODS
  To locate the signal from flowing blood with a consistent backscatter coefficient, the authors estimated the knee of the cumulative Doppler power distribution function. They used a flow-tube phantom to test the use of this knee to locate a radial position that would fall into a region of high shear stress and minimal rouleaux formation. They also studied how well the method normalized fractional moving blood volume estimates of the right renal cortex in a volunteer when simulating different body habitus and in a group of six healthy volunteers to estimate variability.
  
  
  RESULTS
  Over five flow velocities and over undersaturated to severely oversaturated receiver gains, the calculated flow-tube area was a mean 89% +/- 7 (+/- standard deviation) of a standard. In humans, the technique normalized the fractional moving blood volume estimates over an 8-dB receiver gain variation; the mean +/- standard deviation of fractional moving blood volume estimates for the six volunteers was 37.6% +/- 3.6.
  
  
  CONCLUSIONS
  Vascularity estimates with power Doppler US are feasible with a normalization scheme based on the cumulative Doppler power distribution function.
authors.affiliation: Department of Radiology, University of Michigan Hospitals, Ann Arbor 48109, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Rubin
authors.forename: R O
authors.initials: RO
authors.lastname: Bude
authors.forename: J B
authors.initials: JB
authors.lastname: Fowlkes
authors.forename: R S
authors.initials: RS
authors.lastname: Spratt
authors.forename: P L
authors.initials: PL
authors.lastname: Carson
authors.forename: R S
authors.initials: RS
authors.lastname: Adler
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001808:Blood Vessels / Q000000981:diagnostic imaging*; D001810:Blood Volume; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D019047:Phantoms, Imaging; D018615:Ultrasonography, Doppler, Color / Q000379:methods