A new technique that combines saline contrast hysterosonography with three-dimensional surface rendering for the visualization of uterine intracavitary pathologies is described. A total of 32 patients suspected of having uterine cavity pathologies on the basis of previous ultrasonography, hysterosalpingography or hysteroscopy were involved in the study. They were examined by three-dimensional high-frequency endovaginal probes (Combison 530, Kretztechnik, Zipf, Austria), with normal saline used as an expander and contrast medium. Three perpendicular planes could be evaluated simultaneous, and surface renderings were readily available. Following the instillation of normal saline, the uterine cavity appears as an echo-free, well-defined structure, and the endometrium appears as an echogenic homogeneous lining around the cavity. Data acquisition time is short and images can be stored for later evaluation. Surface rendering of polypoid structures shows echogenic masses on a pedicle protruding into the uterine cavity. Submucous fibroids appear as mixed echogenic sites bulging into the cavity. Intrauterine synechiae appear as bands of varying thickness traversing the uterine cavity. Simultaneous display of the zone of interest in three perpendicular planes enhances imaging capabilities, while surface rendering provides a comprehensive overview of the surface area of the findings and their topographical orientation. Further research using this new technique is required to document its real contribution to ultrasonographic imaging.

Deformations of the extremities with limb reduction are rare congenital defects which affect one in 1692 live babies. Three-dimensional ultrasound can be of value in the prenatal diagnosis of such deformities. We present a case of upper phocomelia and congenital thrombocytopenia (TAR syndrome). Visualization of the upper extremities was achieved by three-dimensional ultrasound after surface and volume rendering. This new technique allows imaging not only of surfaces like the fetal skin, but also of internal structures like the fetal skeleton.

No abstract

Three-dimensioned (3D) sonography enables the examiner to store, instead of copies from single B-scan planes, a volume consisting of 300 scan planes. The volume is displayed on a monitor in form of three orthogonal planes--longitudinal, axial and coronal. Translation and rotation facilitates anatomical orientation and provides any arbitrary plane within the volume to generate organ optimized scan planes. Different algorithms allow the extraction of different information such as surface, or bone structures by maximum mode, or fluid filled structures, such as vessels by the minimum mode. The volume may contain as well color information of vessels. The digitized information is stored on a magnetic optical disc. This allows virtual scanning in absence of the patient under the same conditions as the volume was primarily stored. The volume size is dependent on different, examiner-controlled settings. A volume may need a storage capacity between 2 and 16 MB of 8-bit gray level information. As such huge data sets are unsuitable for network transfer, data compression is of paramount interest. 100 stored volumes were submitted to JPEG, MPEG, and biorthogonal wavelet compression. The original and compressed volumes were randomly shown on two monitors. In case of noticeable image degradation, information on the location of the original and compressed volume and the ratio of compression was read. Numerical values for proving compression fidelity as pixel error calculation and computation of square root error have been unsuitable for evaluating image degradation. The best results in recognizing image degradation were achieved by image experts. The experts disagreed on the ratio where image degradation became visible in only 4% of the volumes. Wavelet compression ratios of 20:1 or 30:1 could be performed without discernible information reduction. The effect of volume compression is reflected both in the reduction of transfer time and in storage capacity. Transmission time for a volume of 6 MB using a normal telephone with a data flow of 56 kB/s was reduced from 14 min to 28 s at a compression rate of 30:1. Compression reduced storage requirements from 6 MB uncompressed to 200 kB at a compression rate of 30:1. This successful compression opens new possibilities of intra- and extra-hospital and global information for 3D sonography. The key to this communication is not only volume compression, but also the fact that the 3D examination can be simulated on any PC by the developed 3D software. PACS teleradiology using digitized radiographs transmitted over standard telephone lines. Systems in combination with the management systems of HIS and RIS are available for archiving, retrieval of images and reports and for local and global communication. This form of tele-medicine will have an impact on cost reduction in hospitals, reduction of transport costs. On this fundament worldwide education and multi-center studies becomes possible.

Cardiotocography signals were sampled during labour in 53 patients. A recurrent artificial neural network with hidden layer feedback was trained and performance was compared with that of several conventional systems. Correct and false positive rates of all systems tested were calculated. To ensure that the performance of neural networks was not just caused by using different cut-off levels, the threshold used for conventional methods were also adapted and optimised. The correct positives rate of neural networks was between 0.72 and 0.9, and the false positive rate between 0.2 and 0.4. Before optimising, conventional algorithms produced a very low correct positive (0.02-0.5) and a low false positive rate (0.0-0.08). After adjusting the parameters, the tested neural networks still performed better than optimised conventional systems.