OP10.09: A novel semi-automated (SA) technique for 3D ultrasound measurement of placental volume

Authors

  • G. N. Stevenson,

    Corresponding author
    1. Institute of Biomedical Engineering, Department of Engineering Science, Oxford University, Oxford, United Kingdom
    • Institute of Biomedical Engineering, Department of Engineering Science, Oxford University, Oxford, United Kingdom.
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  • S. L. Collins,

    1. Fetal Medicine Unit, John Radcliffe Hospital, Oxford, United Kingdom
    2. Nuffield Department of Obstetrics and Gynaecology, John Radcliffe Hospital, Oxford, United Kingdom
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  • L. Impey,

    1. Fetal Medicine Unit, John Radcliffe Hospital, Oxford, United Kingdom
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  • A. Noble

    1. Institute of Biomedical Engineering, Department of Engineering Science, Oxford University, Oxford, United Kingdom
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Objectives

To develop a new SA volumetric technique for segmentation of the placenta that performs concordantly or better than manual delineation or the current state-of-the-art SA method, VOCAL (GE Medical Systems, Milwaukee, WI, USA).

Methods

3D US scans of the placenta were performed on 10 women with anterior placental implantation and a maternal BMI < 25. Two observers (GS, SC) performed measurement of placenta volume manually, using VOCAL and using the new SA volumetric method on the same scan. Measurement was repeated three times for each technique. Statistical analysis was performed on the volume results. Measurement difference was illustrated by Bland-Altman plot between both automated measures and manual. Evaluation of inter/intra observer variability was performed using intra-class correlation (ICC), having tested for normality of the data using the Lillefors test.

Results

For Observer 1, mean difference (MD) between new method and manual was − 0.776 ml (LOA 14.03, − 15.58) and between VOCAL and manual − 1.5329 ml (LOA 9.29, − 12.36). For Observer 2, MD between new method and manual was − 6.20 ml (LOA 10.64, − 23.05) and between VOCAL and manual − 9.59 ml (LOA 11.17, − 30.34). Table 1 shows the ICC values for inter/intra-observer variability for placental volume.

Table 1. OP10.09: Table 1. Intra-observer & inter-observer variability by measurement type
 Intra-observer variability 
  Inter-observer
Measurement typeICC (95% CI)—Observer 1ICC (95% CI)—Observer 2variability ICC (95% CI)
Manual0.978 (0.939, 0.994)0.904 (0.759, 0.973)0.943 (0.884, 0.972)
New method0.968 (0.913, 0.991)0.957 (0.883, 0.988)0.906 (0.814, 0.954)
VOCAL0.911 (0.773, 0.975)0.928 (0.813, 0.98)0.793 (0.612, 0.895)

Conclusions

Results show that the new method is concordant with manual segmentation based on ICC values for intra/inter-observer variation and mean difference. The new method would appear to produce concordant results to manual segmentation and outperforms VOCAL in aspects of observer repeatability/agreement. This accurate, time-efficient method to calculate placental volume has the potential to become a promising research tool.

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