Inversion mode: a new volume analysis tool for 3-dimensional ultrasonography.
OBJECTIVE
The main goal was to introduce the inversion mode as a new image analysis tool for the examination of fluid-filled structures using 3-dimensional ultrasonography during pregnancy.


METHODS
Three-dimensional ultrasonography was performed on fetuses having fluid collections of noncardiac origin. Threshold adjustment was used to visually assign full transparency to voxels that were associated with fluid. A new postprocessing tool, called the inversion mode, was activated to transform this region of interest into opaque voxels. The morphologic appearance of fluid collections and their anatomic relationship to other organs were shown in this manner.


RESULTS
Diagnostic features were shown by this technique in several fetuses with problems that included pleural effusion, duodenal atresia, urinary tract abnormalities, and hydrocephaly. Furthermore, the inversion mode also permitted surface reconstruction of an irregular pleural effusion that had close resemblance to results with the Virtual Organ Computer-Aided Analysis rotational slice technique. Acoustic shadowing was also documented as a potential technical limitation of this method.


CONCLUSIONS
The inversion mode can display scattered or contiguous fluid-filled structures in ways that can be very difficult or impossible to accurately characterize with conventional ultrasonography. It may be particularly helpful for the evaluation of multiple fluid-filled cysts or irregular fluid collections in the fetus.
Lee
Wesley
W
Division of Fetal Imaging, Department of Obstetrics and Gynecology, William Beaumont Hospital, 3601 W Thirteen Mile Rd, Royal Oak, MI 48073-6769, USA. wlee@beaumont.edu
Gonçalves
Luis F
LF
Espinoza
Jimmy
J
Romero
Roberto
R
D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging*; D005865:Gestational Age; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D011247:Pregnancy; D016216:Ultrasonography, Prenatal / Q000379:methods*