Spatiotemporal image correlation-derived volumetric Doppler impedance indices from spherical samples of the placenta: intraobserver reliability and correlation with conventional umbilical artery Doppler indices

Authors

  • A. W. Welsh,

    Corresponding author
    1. School of Women's and Children's Health, University of New South Wales, Randwick, NSW, Australia
    2. Department of Maternal-Fetal Medicine, Royal Hospital for Women, Randwick, NSW, Australia
    • Department of Maternal-Fetal Medicine, Royal Hospital for Women, Locked Bag 2000, Barker Street, Randwick, NSW 2031, Australia.
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  • M. Hou,

    1. Faculty of Medicine, University of New South Wales, Randwick, NSW, Australia
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  • N. Meriki,

    1. School of Women's and Children's Health, University of New South Wales, Randwick, NSW, Australia
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  • W. P. Martins

    1. Departamento de Ginecologia e Obstetricia da Faculdade de Medicina de Ribeirao Preto, Universidade de Sao Paulo (FMRP-USP), Ribeirao Preto, Brazil
    2. Escola de Ultra-sonografia e Reciclagem Medica de Ribeirao Preto (EURP), Ribeirao Preto, Brazil
    3. Instituto Nacional de Ciencia e Tecnologia (INCT) de Hormonios e Saude da Mulher, Ribeirao Preto, Brazil
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Abstract

Objective

Volumetric impedance indices derived from spatiotemporal image correlation (STIC) power Doppler ultrasound (PDU) might overcome the influence of machine settings and attenuation. We examined the feasibility of obtaining these indices from spherical samples of anterior placentas in healthy pregnancies, and assessed intraobserver reliability and correlation with conventional umbilical artery (UA) impedance indices.

Methods

Uncomplicated singleton pregnancies with anterior placenta were included in the study. A single observer evaluated UA pulsatility index (PI), resistance index (RI) and systolic/diastolic ratio (S/D) and acquired three STIC-PDU datasets from the placenta just above the placental cord insertion. Another observer analyzed the STIC-PDU datasets using Virtual Organ Computer-aided AnaLysis (VOCAL) spherical samples from every frame to determine the vascularization index (VI) and vascularization flow index (VFI); maximum, minimum and average values were used to determine the three volumetric impedance indices (vPI, vRI, vS/D). Intraobserver reliability was examined by intraclass correlation coefficients (ICC) and association between volumetric indices from placenta, and UA Doppler indices were assessed by Pearson's correlation coefficient.

Results

A total of 25 pregnant women were evaluated but five were excluded because of artifacts observed during analysis. The reliability of measurement of volumetric indices of both VI and VFI from three STIC-PDU datasets was similar, with all ICCs ≥ 0.78. Pearson's r values showed a weak and non-significant correlation between UA pulsed-wave Doppler indices and their respective volumetric indices from spherical samples of placenta (all r ⩽ 0.23). VOCAL indices from specific phases of the cardiac cycle showed good repeatability (ICC ≥ 0.92).

Conclusion

Volumetric impedance indices determined from spherical samples of placenta are sufficiently reliable but do not correlate with UA Doppler indices in healthy pregnancies. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.

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