Standardization of power Doppler quantification of blood flow in the human fetus using the aorta and inferior vena cava.
OBJECTIVE
This study aimed to test the applicability to the fetus of mathematical techniques developed to standardize power Doppler indices of adult regional perfusion.


METHODS
Fetal power Doppler imaging was performed on 14 fetuses (25-37 weeks' gestation) using a standardized parasagittal plane, examining renal and aortic blood flow, and additionally inferior vena caval (IVC) flow in one fetus. Images were stored and transferred for off-line computer analysis using purpose-designed software. We first tested the need for techniques to remove the effects of red blood cell clumping on power Doppler amplitude, then performed further analyses to: (1) investigate cardiac cycle effects on aortic amplitude; (2) determine the spatial consistency of, and influence of angle of insonation on, maximal pixel value; (3) quantify temporal consistency; and (4) compare peak pixel values in the fetal aorta and IVC.


RESULTS
No rouleaux effect on the vascular profile was detectable, in contrast to that identified in the adult. Within each fetus a consistent value was seen in the center of the aorta corresponding to 100% vascular amplitude, which was unaltered by the phase of the cardiac cycle, with a coefficient of variation of 28.9% at 89 degrees and 6.5% at 73 degrees . This value was constant in the aorta and IVC.


CONCLUSIONS
Fetal blood does not appear to form rouleaux to any significant degree, so there is no artificially elevated maximal value for power Doppler amplitude as seen in the adult. We propose that the value representing 100% amplitude may be consistently measured in the center of large fetal vessels such as the aorta, allowing the direct measurement of fractional moving blood volumes in the human fetus.
Welsh
A W
AW
Department of Obstetrics, Royal Prince Alfred Hospital, Camperdown, Australia. alec.welsh@email.cs.nsw.gov.au
Rubin
J M
JM
Fowlkes
J B
JB
Fisk
N M
NM
D000328:Adult; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging* / Q000502:physiology; D001783:Blood Flow Velocity; D005260:Female; D005333:Fetus / Q000098:blood supply*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D009200:Myocardial Contraction; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D012039:Regional Blood Flow; D018608:Ultrasonography, Doppler / Q000379:methods*; D016216:Ultrasonography, Prenatal / Q000379:methods*; D014682:Vena Cava, Inferior / Q000000981:diagnostic imaging* / Q000502:physiology