[Checking and clinical application of time gain compensation (TGC) in diagnostic ultrasonography (author's transl)].

The usefulness of TGC depends on the scanning technique. The A- and B-scan echograms of the orbit can show much more detailed information of the orbital structures, if TGC and a corresponding scanning technique are applied. The sound beam should be directed preferably through the center of the eyeball to keep the length of vitreous within the sound beam constant. The external eye muscles, orbital fat and optic nerve can much better be identified and localized. Radiolucent orbital foreign bodies (wood splinters) were experimentally examined and could also be shown much better using TGC. The TGC characteristic must be measured for reproducible adjustments. The scale readings of the apparatus are insufficient. Even in apparatus supplied with an indication of the TGC characteristic on the screen checking of the real TGC characteristic proved necessary. A simple measurement technique, easily applicable under hospital conditions is described. It is based on a test reflector made from material for soft corneal contact lenses (testreflector W 38, Poly-HEMA, 38% water content.