Influence of Imaging Angle in Measurement of Cisterna Magna

"The length measurement on the fetal cisterna magna (CM) with an angle of 0° between the transducer and the axial cerebellar plane of the fetal head (midline structures will be perpendicular to the ultrasound beam). After that, CM will be measured again after moving the transducer approximately 30° towards the fetal occiput.~Measurements will be performed on the axial cerebellar plane using internal landmarks including the cavum septi pellucidi, thalamus, third ventricle, cerebral peduncles and cerebellar hemispheres.The anteroposterior measurement will be made between the posterior border of the cerebellar vermis and the internal face of the occipital bone.~All the ultrasonography examinations were performed abdominally, using 3-5 megahertz (MHz) transducers."