Video systems have the potential to pay large services with regard to high quality image provision in teleconsultations between physicians and specialists or between physicians and patients. However, a few important conditions need to be fulfilled in order to benefit to the full extent of both the material and intellectual resources which telemedicine has to offer with regard to accurate diagnosis. Electronic interaction or store-and-forward traffic between two sites implies competent operators and excellent voice and image quality. Currently, there exists a range of specialized components which can be inserted between the video source and the transmission medium to enhance the transfer quality of anatomical data, radiology scans, ultrasound, infrared images, pathology specimens, ECG traces, and so on.
The auxiliary tools for telemedical consultation are most required by the physician at the receiving location, who initially has been asking for diagnostic assistance. Nevertheless, the doctor at the consulting site may equally experience the need for additional equipment, enabling better image analysis or specification of an image portion. The auxiliary features are designed to provide superior image quality; management of multiple image sources; format conversion; image comparison; identification of significant areas of interest; correction of optical paths; and storage.
The video switcher is used to accept several television signals at the same time and to route the selected one to the receiving site, which may be a medical image transmission system, a tape recorder, or another TV monitor. No cabling is needed for this operation. The distribution amplifier is able to send one single video signal simultaneously to a number of different remote locations for connection to other help devices, avoiding undesirable interactions, such as loss of signal amplitude or "ghosting". For the electronic reversion of a video image from left to right, the video mirror has been developed. This tool rectifies the false orientation of the image, intercepted by a mirror, for instance in the case of an overhead view during a surgical intervention.
In order to make specific details in the image more visible, the video contrast enhancer can modify the original video signal by means of shading or brightness compensation or by using preselected grey scale levels to introduce picture contrast. It can even produce a negative image through complete reversal of grey scale. You can also create all kinds of marking patterns in black, white, or grey and superimpose them on a medical image with use of a video pointer to generate an artificial TV signal. The split-screen generator acts according to its name. It provides the possibility to display several images from various video sources on the same monitor screen, horizontally, vertically, or with variable size insertions. Of course, the video devices do have to possess a common synchronization source.
To stabilize the playback of videotape recordings and to synchronize different video sources, the video time base corrector is applied in order to produce overlay images. The pseudo-colour generator introduces colours into black-and-white video images, in correspondence with the relative amplitudes of components in the input signal. It is used for the display of thermography and radiation energy levels. In order to transform the scanning rates into traditional TV standards, it is best to rely on a scan converter for matching the visual output of medical imaging equipment to the input of a local distribution network.
Two remaining useful devices are the video subtractor, used for displaying the differences between two images, and the video peak store memory for the generation of time-exposure images of physical movements. If you connect a computer to a telediagnostic system, the range of possibilities becomes enormous because you can implement software programmes for image manipulation and storage for future transfers. It goes without saying that these technologies require the right kind of expertise. Not the tools provide the magic, but the people behind them. The contents of this article is based on a story, written by Glen Southworth, for the Telemedicine and Telehealth Networks magazine.