Biomedical Engineering Reference
In-Depth Information
Fig. 2.13.
Three orthogonal sectional images of a fetus in the first trimester by 3D
ultrasound
Defocusing Lens Method
This method is basically tomography with a thick slice [13,15], but an image
just like a transparent 3D image can be obtained. Even a surface image can be
obtained under some conditions. The image is recognized three-dimensionally
by its observer when the probe is rotating. Real-time observation is possible,
but the applications are very limited because the structure surrounding the
fetus makes the fetal image obscure.
Real-Time Ultrasonic Beam Tracing
This is the latest method in 3D ultrasound [16,17]. Generation of a 3D image
and 3D data acquisition are done simultaneously in this method, and a com-
plete 3D image is displayed on the monitor when a 3D scan is completed. This
is the most promising method for real-time 3D ultrasound [18]. By selecting
parameters, a 3D fetal skeletal image can be obtained as well as a 3D fetal
surface image.
2.2.3
Clinical Applications of Three-Dimensional Ultrasound
in Obstetrics
Three-dimensional ultrasound has not been popularized. But its significance
in obstetrics has been recognized widely [19].
First Trimester
Three orthogonal sectional displays by 3D ultrasound enable the examiner to
locate a gestational sac in the uterus more accurately and to measure crown-
rump length (CRL) for gestational age confirmation and nuchal translucency
