[Three-dimensional ultrasonography. Experience with a non-dedicated system].

The application of three-dimensional (3D) reconstructions to US has been recently proposed, but remains strongly limited by the difficulty to produce parallel and equidistant slices and by the obvious lack of method standardization. This work describes our experience with a workstation on the market in producing 3D images from US exams. Reconstruction involved the following steps: acquisition (US examinations of different organs--i.e. carotid artery, parotid gland, kidney, gallbladder, urinary bladder--were recorded on VHS tape; a small, self-built, motor-driven mechanical arm was used to move the probe along the selected axis of the organ: a 486-class computer with a framegrabbing card was used during the digitizing process to produce a set of slices, white were saved in 320 x 256 x 8 bit format), pre-processing and segmentation (we used interactive contrast enhancement as a pre-processing technique, to emphasize contrast between echoic and anechoic structures or between solid structures with a small difference in echogenicity; as a segmentation technique, we used autotracing with a selected seed point; in a small number of images, where the software could not provide an adequate delimitation, we had to operate manually) and rendering. A commercially available software for radiological use (Analyze-Mayo Foundation, USA) was used for processing, segmentation and rendering. The rendered images can be visualized with multiple zoom factors, rotated and cut on any plane, reconstructed from every user-definable point of view. The good results indicate that 3D acquisition and reconstruction will probably change the way to obtain, display and study US findings.