Teleradiology

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Abstract
Applications The range of potential applications for teleradiology is large, stretching from simple lap top computer based systems transmitting static images to fully interactive, real time, picture interrogation. The most basic system uses equipment often already available in most radiology departments. Digitised low resolution images such as are found in computed tomography and magnetic resonance imaging are transmitted over an existing telephone line to a work station based on a personal computer; this may be at another hospital or in a doctor's home. The most recent software packages for a system such as this could be installed for less than pounds sterling5000, with prices continuing to fall steadily. Real time video systems are now commercially available. These are most suitable for applications such as ultrasonography, in which a trained radiographer may carry out an examination with interactive supervision from a radiologist. One radiologist would therefore have the potential to supervise several examinations from different places almost simultaneously. There are two common methods of image transfer. A coder-decoder (known as a CODEC) transforms analogue images to digital information and compresses the data. At the remote site another CODEC decompresses the signal and changes it to analogue for viewing on a monitor. A camera and microphone with pan, zoom, and tilt capabilities is located at each of the remote sites and at the hub site. One camera views the patient and radiographer while the other transmits the real time ultrasound image. The cost for a state of the art system such as this remains prohibitively expensive. Currently telephone lines are being upgraded to enable such real time images to be transmitted within the United Kingdom. Although interactive video conferencing has received most attention in the press, many advocates of teleradiology believe that simpler less expensive “store and forward” systems (figure) will become the popular choice.2 In a store and forward system static images are acquired and transmitted one by one to the hub site. On the basis of an assessment in Oklahoma, 85% of needs can be met in near real time using such technology. Such systems are currently available in the United Kingdom, although uptake as yet has been poor. To allow fast transmission of images the data for digital images must first be compressed. Generally, the greater the compression the faster the transmission but unfortunately the greater the risk of losing detail. Computed tomograms and magnetic resonance images are readily compressible because the images remain of diagnostic quality even when reconstructed with relatively low resolution. Standard plain film radiographs, however, can tolerate much less compression if they are to remain of diagnostic quality. Plain radiographs are now readily transmitted in the United States, but radiologists remain divided on whether the detail of the received image is of sufficient diagnostic quality. Currently, the high resolution required for mammography makes mammograms unsuitable for transmission.

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