Three-dimensional inversion rendering: a new sonographic technique and its use in gynecology.

OBJECTIVE: The purpose of this presentation is to describe the use of the 3-dimensional (3D) sonographic inversion rendering mode in displaying fluid-filled structures using dedicated hardware and software in gynecology. METHODS: The 3D software used inverts anechoic into echogenic voxels, which, against the black background of the monitor screen, display the fluid-filled structure as a "cast" of it. The technique of the rendering process is described. Three-dimensional sonographic volumes of the adnexal area in 3 patients thought to have adnexal or ovarian masses were stored and rendered with the use of the laptop version of the inversion software. The same process was used in an additional 12 women for various indications: 7 with suspected uterine malformations and 5 with uterine bleeding. Of these 12 women, 11 underwent saline infusion sonohysterography. RESULTS: Rendering the inverted fluid-filled adnexal structures revealed that, in all 3 cases, they were tubal, not ovarian, in origin (chronic hydrosalpinges). Of the 7 uterine cavities suspected of malformation, 3 were normal and 4 had uterine malformations: 2 arcuate uteri and 2 incomplete septate uteri. Of the 4 woman with dysfunctional uterine bleeding, 3 had endometrial cavities with polyps and 1 had an irregular surface of the cast. One woman with postmenopausal spotting had an enlarged but otherwise normal cavity. CONCLUSIONS: After a relatively short learning curve to master the inversion rendering technique, it is possible to use it in a selected number of gynecologic cases with fluid-filled structures. In resolving the correct diagnosis of the adnexal masses, the inversion images performed better than the 2-dimensional (2D) and 3D orthogonal planes. For diagnosis of uterine disease, the inversion pictures presented marginal value over the 2D and 3D images. The 3D inversion rendering technique may have added value in selected gynecologic cases, establishing a more accurate diagnosis somewhat faster than only 2D sonography or even the 3D orthogonal planes.