Fetal cerebellar volume and symmetry on 3-d ultrasound: volume measurement with multiplanar and vocal techniques.

The purpose of this prospective longitudinal study was to evaluate the growth of the fetal cerebellar volume by means of 3-D ultrasound to evaluate whether there is a difference between the volumes of the left and right cerebellar hemispheres, and to evaluate the intra- and interobserver reliability of two different techniques of volume measurement. Three-dimensional ultrasound examinations were performed every two to three weeks on 27 fetuses between 20 and 40 weeks' gestation. Measurements of the total cerebellar volume and of the left and right cerebellar hemispheres were done using the multiplanar technique. Multilevel analysis was used to determine the growth of cerebellar volume based on individual developmental trajectories and compare the volume of the right and left hemispheres of the cerebellum. The intra- and interobserver reliability was calculated for the multiplanar and VOCAL techniques in a subgroup of 10 fetuses. A nonlinear growth curve of cerebellar volume in normal pregnancy was generated. The cerebellar growth per two-week decreased from a gain of 51% of the first measurement at 20 weeks to a gain of 16% of the first measurement at 38 weeks. The left cerebellar hemisphere was significantly larger (12.3%, p < 0.01) than the right. The intraclass correlation coefficient for the measurements by the two techniques was 0.99. Intraobserver reliability: the intraclass correlation coefficient for the measurements using the multiplanar technique was 0.96 and 0.97 and for VOCAL it was 0.98 and 0.97 for the two observers, respectively. Interobserver reliability: the intraclass correlation coefficient for the measurements using the multiplanar technique was 0.97 and for VOCAL 0.98. Longitudinal growth curves based on individual developmental trajectories were generated for the cerebellar volume. The left fetal cerebellar hemisphere was found to be significantly larger than the right. Both multiplanar and VOCAL techniques had a good intra- and interobserver reliability and yielded very similar results.