Re: Gestational sac volume: comparison between SonoAVC and VOCAL measurements at 11 + 0 to 13 + 6 weeks of gestation

A new semi-automated method for fetal volume measurements with three-dimensional ultrasound: preliminary results

OBJECTIVE

Complications in pregnancy are suggested to be the result of intrauterine conditions in the first trimester of pregnancy. Three-dimensional ultrasound volume measurements might give more information, compared with two-dimensional measurements. Commonly available methods for volume measurements are not suited for daily practice. This is a report of preliminary results of a promising, more practical semi-automated method for volume calculations with three-dimensional ultrasound.

METHOD

Volume datasets of 16 objects (10.2-41.5 cm(3) ) were obtained. Euclidean shortening flow and Perona and Malik were used as image enhancement techniques. The image gradient was calculated. The points of interest were detected by the iso-intensity and the edge-detection technique. Volume measurements with Volume Computer-aided AnaLysis (VOCAL) are used as a reference. A volume dataset of a first trimester fetus was acquired to test this method in vivo.

RESULTS

The mathematical calculations with iso-intensity (Perona and Malik: average= -1.57 cm(3) , SD=4.05; and Euclidean shortening flow: average= -1.38 cm(3) , SD=2.47) showed results comparable with the VOCAL method (average= +1.28 cm(3) , SD=2.07). We also succeeded in detecting all voxels in the whole contour of a 12-week fetus.

CONCLUSION

Mathematical volume calculations are possible with the semi-automated method. We were able to apply this new method on a first trimester fetus. This new method is promising for future use in the daily practice.

Embryo volume measurement: an intraobserver, intermethod comparative study of semiautomated and manual three-dimensional ultrasound techniques

OBJECTIVE

To compare the reliability of our recently introduced technique for first-trimester embryo volume measurement, the 'semiautomated technique' using both Virtual Organ Computer-aided AnaLysis (VOCAL(™) ) and Sonography-based Automated Volume Count (SonoAVC) with a manual technique using VOCAL alone.

METHODS

Seventy-four subjects with viable, singleton first-trimester in-vitro fertilization (IVF) pregnancies were recruited. Each subject underwent transvaginal sonography, at which a three-dimensional ultrasound dataset of the entire gestational sac was acquired. Each embryo volume was measured by two techniques, each performed twice. In the semiautomated technique VOCAL was used to calculate the volume of the gestational and yolk sacs, and SonoAVC was used to quantify the fluid volume within the amniotic and extra-amniotic cavities. Embryo volume was calculated by subtracting the sum of yolk sac, amniotic and extra-amniotic fluid volumes from gestational sac volume. In the manual technique, VOCAL was used to delineate the entire embryo using 9° rotations. Reliability was assessed using limits of agreement and intraclass correlation coefficient.

RESULTS

Datasets were included from 52 eligible subjects. Median gestational age was 7 + 4 weeks; median crown-rump length (CRL) was 13 (range, 2-29) mm; and median embryo volume was 1.8 (range, 0.03-8.1) cm(3) using the semiautomated technique and 0.7 (range 0.009-3.6) cm(3) using the manual technique. There was a significant discrepancy in the volumes measured by the two different techniques. Assessment of the limits of agreement suggested that the semiautomated technique (-15.8% to 14.0% of the mean embryo volume) was more reliable than was the manual technique (-22.4% to 26.6%).

CONCLUSION

The semiautomated technique is more reliable than is the manual technique for embryo volume measurement. However, the discrepancy in measurements between the two methods raises concerns over the validity of the semiautomated technique that require further investigation.