OP09.11: Three‐dimensional gestational sac volumetry as the new biometric parameter and the intraobsever and interobserver reproducibility

Abstract

The purpose of this study was to establish a method for determination of gestational sac volume (GSV) by three-dimentional ultrasonography with the VOCAL (Virtual Organ Computer-aided Analysis) program in early pregnancy. The cross-sectional study has been conducted in 336 uncomplicated singleton pregnancy. In the contour generation of gestational sac, both automatic and manual tracing mode of the VOCALTM was applied for the comparison between two methods. In order to verify the intra- and interobserver reproducibility of gestational sac volumetry, in 207 cases gestational sac volumes were measured by the same sonographer twice and also by a second sonographer once. Polynomial regression analysis was performed for the nomogram of gestational sac and its reference interval. To determine intraobserver and intraobserver reproducibility, intra-correlaton coefficient (intra-CC) and intercorrelation coefficient (inter-CC) was expressed. Three-dimensional volumetry demonstrated the exponential growth pattern between gestational age and GSV by automatic tracing mode [GA = 35.1 + 5.53GSV (a) 1/2–0.0000092GSV (a) 3, GA: gestational age, GSV (a): GSV by automatic tracing mode, R2: 0.788, p < 0.0000] and GSV by manual tracing mode [GA = 35.1 + 5.53GSV (m) 1/2–0.000092GSV (m)3, GSV (m): GSV by manual tracing mode), R2: 0.818, p < 0.0000]. The reference interval of GSV also was increased as the pregnancy progression. Reliable consensus was observed for both the intra-CC and inter-CC for two types of gestational sac volumetry [intra-CC for GSV (a) and for GSV (m), inter-CC for GSV (a) and GSV (m): 0.9987, 0.9905, 0.9658, 0.9375, respectively]. We can conclude that three-dimensional GSV with the rotational technique of the VOCAL-imaging program can be used as the new biometric measurement in determining gestational age. Gestational sac volumetry can be easily obtained with automatic tracing mode of the VOCAL- imaging program.