Three-dimensional ultrasound in obstetrics and gynaecology: technique, possibilities and limitations.

Three-dimensional (3D) ultrasound offers several options extending conventional two-dimensional scanning. Various imaging modes are available. Three perpendicular planes displayed simultaneously can be rotated and translated in order to obtain accurate sections and suitable views needed for diagnosis and geometric measurements. 3D ultrasound tomography combines the advantages of ultrasound, e.g. safety, simplicity of application and inexpensiveness, with the advantages of sequentially depictable sections in numerous rotatable and translatable sections. Surface rendering gives detailed plastic images if there are surrounding layers of different echogenicity allowing for the definition of a certain threshold. Transparent modes provide an imaging of structures with a higher echogenicity in the interior of the object. A combination of the two modes sequentially definable by the sonographer allows for the optimal viewing of structures. These imaging modes are innovative features which have to be evaluated for clinical applicability and usefulness. Digital documentation of whole volumes enables full evaluation without loss of information at a later point. 3D technology provides an enormous number of technical options which have to be evaluated for their diagnostic significance and limitations in obstetrics and gynaecology.