Image Optimization 5-45
5.11.2 Note before Use
NOTE:
In accordance with the ALARA (As Low As Reasonably Achievable) principle, please try to
short the sweeping time after a good 3D imaging is obtained.
The quality of images reconstructed in the freehand 3D mode is closely related to the fetal condition,
angle of a B tangent plane and scanning technique.The following Smart 3D description uses the fetal
face imaging as an example, the other parts imaging are same as 3D/4D imaging.
Fetal Condition
Gestational age
Fetuses of 24~30 weeks old are the most appropriate to 3D imaging.
Fetal body posture
Recommended: Cephalic face up (figure a) or face aside (figure b); NOT recommended:
Cephalic face down (figure c).
a
b
c
Amniotic fluid (AF) isolation
The region desired is isolated by amniotic fluid adequately
The region for imaging is not covered by limbs or umbilical cord.
The fetus keeps still.If there is a fetal movement, you need a rescan when the fetus is still.
Angle of a B tangent plane
The optimum tangent plane to the fetal face 3D imaging is the sagittal section of the face.To ensure
high image quality, you’d better scan maximum face area and keep edge continuity.
Image quality in B mode (2D image quality)
Before entering 3D capture, optimize the B mode image to ensure:
High contrast between the desired region and the amniotic fluid surrounded.
Clear boundary of the desired region.
Low noise of the amniotic fluid area.
Scanning technique (only for Smart 3D)
Stability: body, arm and wrist must move smoothly, otherwise, the restructured 3D image
distorts.
Slowness: Move or rotate the transducer slowly. The speed of linear scan is about 2 cm/s and
the rotation rate of the fan scan is about 10°/s
～
-15°/s.
Evenness: move or rotate the transducer at a steady speed or rate.
NOTE:
1. A region with qualified image in B mode may not be optimal for 3D imaging.E.g.
adequate AF isolation for one section plane of 2D image doesn’t mean the whole
desired region is isolated by AF for 3D imaging.
2. More practices are needed for a high success of qualified 3D imaging.
3. Even with good imaging condition, to acquire an approving 3D image may need more
than one scanning.
