Transrectal three-dimensional fetal volumetry and crown-rump length measurement during early gestation in mares: Intra- and inter-observer reliability and agreement

Angela Becsek; Nikolaos Tzanidakis; Miguel Blanco; Heinrich Bollwein

doi:10.1016/j.theriogenology.2018.11.012

Transrectal three-dimensional fetal volumetry and crown-rump length measurement during early gestation in mares: Intra- and inter-observer reliability and agreement

Theriogenology. 2019 Mar 1:126:266-271. doi: 10.1016/j.theriogenology.2018.11.012. Epub 2018 Nov 16.

Authors

Angela Becsek¹, Nikolaos Tzanidakis², Miguel Blanco³, Heinrich Bollwein⁴

Affiliations

¹ Clinic of Reproductive Medicine, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, 8057, Zurich, Switzerland. Electronic address: [email protected].
² Clinic of Reproductive Medicine, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, 8057, Zurich, Switzerland. Electronic address: [email protected].
³ Lewitz Stud, Lewitzhof 1, 19306, Neustadt-Glewe, Germany. Electronic address: [email protected].
⁴ Clinic of Reproductive Medicine, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, 8057, Zurich, Switzerland. Electronic address: [email protected].

PMID: 30590249
DOI: 10.1016/j.theriogenology.2018.11.012

Abstract

The aim of this study was to investigate if transrectal three-dimensional (3D) ultrasound is a reliable technique to measure equine fetal volume (FV) during early gestation in mares. In total 149 warmblood mares were examined once transrectally on days 45 ± 1 of pregnancy with a portable 3D ultrasound device (Voluson^® i, GE Healthcare, Zipf, Austria). The following measurements were performed: Two-dimensional (2D) and 3D crown-rump length (CRL), FV using Virtual Organ Computer-aided AnaLysis (VOCAL™) software with rotational angles of 6° and 30°. To analyze intra- and inter-observer reliability (intraclass correlation coefficient (ICC)) and agreement (Bland-Altman's limits of agreement (LoA)) of FV measurements, images from 60 horse fetuses were selected and repeatedly analyzed by the same examiner (A) and by a second examiner (B). The time for each ultrasound examination (2D and 3D) and for the FV measurements was recorded. The 3D measured CRL was larger (P < 0.001) than the 2D CRL. Repeated measurements of 3D CRL showed a higher reliability (ICC = 0.91 (0.88-0.94), P < 0.001) and agreement (mean = 0.13%, 95% LoA: 7.45 to +7.19) compared to reliability (ICC = 0.50 (0.36-0.61), P < 0.001) and agreement (mean = -1.54%, 95% LoA: 23.29 to +20.21) of the CRL measurement in 2D mode. For intra-observer examinations, reliability was highest when using a rotational angle of 30° (ICC = 0.98 (0.97-0.99), P < 0.001). The inter-observer reliability of 3D measurements was good (ICC = 0.85 (0.67-0.92), P < 0.001). The extra time needed to perform the 3D scan ranged from 1 to 9 min and FV measurements lasted 03:30 ± 00:46 and 08:10 ± 01:05, for rotational angles of 30° and 6°, respectively. In conclusion, this study showed a high level of intra- and inter-observer reliability and agreement for FV measurements using VOCAL™. Furthermore, the 6° and 30° rotational angles can be used interchangeably, but test duration, reliability and agreement were better with the 30° rotational step method. The CRL measurements obtained with 3D mode probably reflects the true CRL, compared to the 2D measured CRL.

Keywords: Crown-rump length; Early gestation; Equine; Fetal volume; Intra- and inter-observer; Three-dimensional ultrasound; VOCAL.

MeSH terms

Animals
Crown-Rump Length
Fetus / anatomy & histology
Fetus / diagnostic imaging*
Gestational Age
Horses / growth & development*
Imaging, Three-Dimensional / veterinary
Observer Variation
Ultrasonography, Prenatal / veterinary