In an X-ray three-dimensional image display apparatus, a rotary encoder unit is employed which determines a window level and width of a two-dimensional image, and furthermore determines both upper and lower threshold limits in an X-ray CT (computerized tomographic) value of an X-ray tomographic image....http://www.google.de/patents/US5229935?utm_source=gb-gplus-sharePatent US5229935 - 3-dimensional image display apparatus capable of displaying a 3-D image by manipulating a positioning encoder
