3D/4D volume ultrasound is an established method that offers various options for analysing and presenting ultrasound volume data. The following imaging techniques are based on automatically acquired ultrasound volumes. The multiplanar view is the typical mode of 3D ultrasound data presentation.
Ultrasound scanning is an important clinical tool in providing images of internal fetal anatomy. It is also called sonography because it uses high-frequency sound waves to produce images of slices through the body. A transducer or probe which emits ultrasound waves is placed on the skin after coating it with a thin layer of conductive gel, to make sure the waves pass smoothly through the skin. The emitted ultrasound waves are reflected by different structures encountered by the waves. The strength of the reflected waves, and the time they take to return, form the basis for interpreting the information into a visible image. This is performed by computer software.
The advantages of ultrasound imaging over other imaging techniques include:
Real-time visualization of the fetus or organs.
Doesn’t use ionizing radiation, which has been associated with toxic effects on the embryo.
Interactive, enabling the operator to capture different viewing planes by moving the probe.
Further development of ultrasound technology led to the acquisition of volume data, i.e., slightly differing 2D images caused by reflected waves which are at slightly different angles to each other. These are then integrated by high-speed computing software. This provides a 3-dimensional image. The technology behind 3D ultrasound thus has to deal with image volume data acquisition, volume data analysis and finally volume display.
4D ultrasound has the same advantages as 3D, while also allowing us to study the motion of various moving organs of the body. Its clinical applications are still being studied. At present it is mostly used to provide fetal keepsake videos, a use which is discouraged by most medical watchdog sites.