Analysis of automatic fetal intracranial volume (ICV) measurement based on the optimized ultrasound Smart ICV method at 16-34 weeks of gestation.

Background: Fetal intracranial volume (ICV) can help evaluate the development of the prenatal central nervous system (CNS) from the three-dimensional (3D) attributes of the cranial structure. Accurate and rapid segmentation and calculation of the ICV are clinically significant. Virtual organ computer-aided analysis (VOCAL) is a commonly used method for measuring fetal ICV. However, its operation is highly complex and time-consuming. This study aimed to optimize the fetal Smart ICV method at 16-19 gestational weeks, verify the consistency of automatic and manual measurement of ICV, and assess an automatic and efficient method for evaluating fetal ICV growth in the second and third trimester of pregnancy.

Methods: The ultrasound data of 950 healthy fetuses at 16-34 weeks of gestation were collected. First, the Smart ICV algorithm was optimized at 16-19 weeks. Second, the optimized Smart ICV was compared with the manual VOCAL method. Finally, growth curve and Z-score estimations for fetuses were established for growth assessment via optimized Smart ICV.

Results: Compared with the nonoptimized version, the optimized Smart ICV yielded a lower Hausdorff distance (1.15±0.25 1.31±0.93 mm, P<0.05). Both intra- and inter-observer agreements were at a high level for ICV measurement based optimized Smart ICV [intra-observer intraclass correlation coefficient (ICC) =0.998, 95% confidence interval (CI): 0.996-0.999; inter-observer ICC =0.991, 95% CI: 0.988-0.996] and the 18 plane-VOCAL (intra-observer ICC =0.997, 95% CI: 0.995-0.998; inter-observer ICC =0.981, 95% CI: 0.979-0.991). Additionally, Bland-Altman analysis showed that the ICV data for the above two models had good agreement. Nevertheless, compared with the 18 plane-VOCAL, the optimized Smart ICV consumed less time (3.7±0.7 153.1±29.5 s, P<0.05). The best fitting model of gestational week for the Smart ICV was a cubic function, expressed as follows: = -44.2445 + 0.1427 + 0.0052 , where is ICV and is the gestational week. In addition, fetal ICV showed an accelerated growth trend in the second trimester.

Conclusions: The optimized Smart ICV showed excellent accuracy and efficiency in ICV measurements at 16-34 gestational weeks. Our results may help to establish a best-fit growth curve for ICV. Our findings suggest that the optimized Smart ICV method has the potential to be a reliable tool for fetal growth assessment during the second and third trimesters.