Dartmouth develops low-bandwidth telesonography system

Current teleradiology image transfer systems were developed for high-bandwidth networks and therefore cannot support radiographs or sonograms from remote or underdeveloped areas due to limited bandwidth availability at those locations.

A new paper (Am J Roentgenol 2007;188[3]:W219-W22) reports on a pilot program that established a low-cost telesonography model with real-time transmission over low-bandwidth connections between a remote clinic in an underdeveloped area and a large U.S. medical center.

"This system of image transfer offers the potential for sonography to be performed at a remote, underdeveloped region and interpreted in real-time at a distance by trained radiologists, thereby extending the presence of physicians in virtual space," said Veljko Popov, an M.D./Ph.D. student at Dartmouth Medical School and lead author of the study.

Several accounts of remote-guided sonography, including transmission from Earth orbit, have been reported, but most telesonography links rely on proprietary hardware and software solutions that require costly high-bandwidth connections between centers, such as T1-T10 lines, intranets, or LANS. But these networks are not readily available to humanitarian missions in developing countries or tertiary medical centers in the U.S.

"Both proprietary hardware and software and costly underlying networks add to system expense, making telemedicine practical only for large medical centers in developed areas whose geographic locations permit high-speed Internet access," Popov said.

The Dartmouth research was facilitated by recent technological advancements in:

• the availability of inexpensive compact sonographic devices;

• the increasing availability of low-bandwidth Internet connections via terrestrial or satellite links; and

• the availability of inexpensive hardware and software solutions for transmission of sonography data in teleconference settings.

The digital conversion of any analog video signal adhering to the National Television Standards Committee (NTSC) system, including sonography, can be achieved with an analog-to-digital conversion card, Popov said. Such cards are commonly used by consumers to transfer videos from tape to CD or DVD formats. Similarly, still or moving images can be readily transmitted between computers by either streaming or teleconferencing.

Teleconferencing applications based on the H.323 protocol, a recommendation from the International Telecommunication Union that is being used in Voice-over-IP (VoIP)- and Internet Protocol (IP)-based videoconferencing, are capable of transmitting video and audio streams in real-time, transferring files, and allowing remote access and control of computers.

"By combining real-time video streams and still-image capture, the bandwidth requirements decreased substantially and image transmission over telephone lines or satellite link becomes possible," Popov said.