Automatic Measurements Of Fetal Intracranial Volume Using Smart ICV

Objective:To use the automatic quantitative analysis tool（Smart ICV）to measure normal and abnormal fetal intracranial volume,which was then compared with virtual organ computer-aided technology（virtual organ computer-aided analysis,VOCAL）and MRI（magnetic resonance imaging,MRI）for consistency,repeatability and length of time taken,and furthermore analyze the relationship between normal fetal intracranial volume and gestational time based on Smart ICV,and evaluate the application value of Smart ICV in measuring fetal intracranial volume.Study method:289 pregnant women（19 to 28 weeks of gestational age）for primary obstetric ultrasound examination were selected as the normal group in Guangdong Maternal and Child Health Hospital between June 2019 and December 2020;meanwhile,92 positive cases with fetal anomalies confirmed by MRI and 32 positive cases with intrauterine growth restriction（IUGR）were selected to verify the results in the normal group.Smart ICV and VOCAL were performed with a Mindray Resona 7Color Doppler Ultrasound Examination Instrument with preset Smart Planes program.A volumetric probe was used to collect 3D volumetric data,Smart Planes CNS was used to process images,and Smart ICV and Smart V Vocal were used to calculate the intracranial volume.MRI was performed with a Ingenia 3.0T MRI（Philips,Netherlands）.Intraclass correlation coefficient（ICC）was used to evaluate the reliability and consistency of Smart ICV and VOCAL in measuring fetal intracranial volume,as well as the consistency of measurements by different examiners.ICC>0.75 was considered to be consistent between different measurements.The Mann-Whitney U test was used to compare the time required for data measurement between the two techniques.Pearson linear correlation analysis was used to analyze the correlation between fetal intracranial volume and gestational age.Results:The fetal intracranial volumes measured by Smart ICV,VOCAL 6 section,VOCAL 12 section and VOCAL 18 section were 114.45（73.80,162.95）cm³,109.63（68.87,158.26）cm³,111.23（70.51,160.18）cm³and 113.15（72.27,161.42）cm³,respectively.The required times were 14.45（13.40,16.03）s,223.45（217.50,229.00）s,293.53（290.78,296.90）s and 385.48（383.55,387.45）s,respectively.The ICCs of the fetal intracranial volume between Smart ICV,VOCAL 6 section,VOCAL 12section and VOCAL 18 section were 0.995[95%confidence interval（CI）:0.172～0.999,P<0.001],0.998（95%CI:0.361～1.000,P<0.001）and 0.999（95%CI:0.828～1.000,P<0.001）,respectively.The required time of Smart ICV was significantly shorter than those of VOCAL（Z=-14.977,-14.977,-14.977,all P<0.001）.The differences of the fetal intracranial volumes between Smart ICV,VOCAL 6section,VOCAL 12 section and VOCAL 18 section were 4.90（4.64,5.16）cm³,3.08（2.82,3.32）cm³and 1.50（1.21,1.80）cm³,respectively.The difference between Smart ICV and VOCAL 18 section was significantly lower than those between Smart ICV,VOCAL 6 section and VOCAL 12 section（Z=-14.977,-14.977,both P<0.001）,and the measurement result of Smart ICV was closer to that of VOCAL 18 section with an average error of 1.52 cm³（1.57%）.1.Verify the effectiveness of Smart ICV in the diagnosis of positive cases.The fetal intracranial volumes measured by Smart ICV,VOCAL 18 sections and MRI in the cases with fetal anomalies were 126.96（93.28,174.89）cm³,125.14（90.86,171.93）cm³and 130.25（87.36,190.47）cm³,respectively.The ICC of Smart ICV between MRI and VOCAL 18 sections were 0.970（95%CI:0.796～0.992,P<0.001）and 0.998（95%CI:0.817～1.000,P<0.001）,respectively.The mean error of intracranial volume between Smart ICV and VOCAL 18 sections was as low as 1.82cm³（1.65%）.The fetal intracranial volumes measured by Smart ICV and VOCAL 18sections in the cases with IUGR were 100.54（59.76,151.08）cm³,98.73（58.47,149.95）cm³,respectively.The ICC was 0.999（95%CI:0.841～1.000,P<0.001）,and the mean error was low as 1.87 cm³（1.76%）.2.The ICCs measured repeatedly by the same operator by Smart ICV were0.996（95%CI:0.993～0.998,P<0.001）,0.995（95%CI:0.164～0.997,P<0.001）and 0.993（95%CI:0.158～0.996,P<0.001）,respectively for the normal group,cases with fetal anomalies and IUGR.The ICCs measured by different operators by Smart ICV was 0.999（95%CI:0.998～1.000,P<0.001）,0.997（95%CI:0.994～0.999,P<0.001）and 0.994（95%CI:0.160～0.997,P<0.001）,respectively for the normal group,cases with fetal anomalies and IUGR.3.The results of Pearson linear correlation analysis showed a high positive correlation between fetal intracranial volume measured by Smart ICV and gestational age（r=0.984,P<0.001）.The curve fitting results show the determination of the S-type curve and the secondary coefficient（R²）up to 0.978,its S-type curve equation was:fetal intracranial volume=e^{（8.283-83.521/gestational week）},and the quadratic curve equation was:fetal intracranial volume=-11.357×gestational week+0.605×gestational week×gestational week+46.227（R²=0.976）.The predicted percentile and growth curve of intracranial volume of the fetus at each gestational week can be calculated according to the quadratic curve equation and the residual value,which can be used to evaluate the gestational time of the fetus.4.External verification of fetal cases in the craniocerebral malformation group and the IUGR group showed that there was a statistically significant difference in intracranial volume between the microcephaly group and fetus from corresponding gestational time,and there was also a statistically significant difference in intracranial volume between the IUGR group and fetus from corresponding gestational time,while there was no statistically significant difference between other fetuses in the craniocerebral malformation group and fetus from corresponding gestational time.Conclusion:The application of intracranial volume automatic quantitative analysis tool（Smart ICV）can quickly and automatically obtain fetal intracranial volume with short time,high accuracy and good consistency with VOCAL measurement and MRI measurement,and the mean error was low and expert measurement accuracy could be achieved.The fetal intracranial volume measured by Smart ICV was highly positively correlated with the gestational age,which had high clinical application value.It has the value of evaluating fetal gestational time and assisting in the diagnosis of microcephaly and IUGR.It could help sonographers to make accurate measurement and judgment of the fetal intracranial volume,and has certain clinical application value in the fetal craniocerebral examination and diagnosis.