Guest Editorial: Special Section on Internet Imaging

Internet imaging differs from otherforms of electronic imaging in that itemploys an internet (network of net-works) as a transmission vehicle. How-ever, the internet is only one compo-nent (albeit a major one) in the totalimaging system. The total system com-prises client applications internet-worked with server applications, aswell as offline authoring tools.The internet is an evolving commu-nication system. Its functionality, reli-ability, scaling properties, and perfor-mance limits are largely unknown. Thetransmission of images over the inter-net pushes the engineering envelopemore than most applications. Conse-quently, the issues we are interested inexploring pertain to all aspects of thetotal system, not just images or imag-ing algorithms.This emphasis on systems is whatsets internet imaging apart from otherelectronic imaging fields. For a localimaging application, even when it issplit between a client and a serverlinked by an Ethernet, a system can bedesigned by stringing algorithms in apipeline. If performance is an issue, it iseasy to identify the weak link and re-place it with a better performing com-ponent.On the internet, the servers are un-known, the clients are unknown, andthe network is unknown. The system isnot easily predictable and the result isthat the most common problem today isscalability. To be successful one has tofollow a top-down design strategy,where the first step is a detailed analy-sis of the problems to be solved. Whena solution is invented, algorithms areselected to produce a balanced sys-tem, instead of choosing algorithms ofbest absolute performance as is donein bottom-up approaches.The paper on the Visible Humanby Figuiredo and Hersch is a good ex-ample illustrating these fundamentals.Today, storing a 49-Gbyte 3-dimen-sional volume is not hard, and a RAIDdisk array can deliver fast accesstimes. However, storage space andseek time are not the limiting factors forthe extraction of ruled surfaces fromlarge 3-dimensional medical images.The problem is one of load balancing,which requires detailed performancemeasurements for scalability. Eventu-ally, a specialized parallel file stripingsystem must be designed and opti-mized. Implementing and maintaining asystem that must grow as more databecomes available and as surgeons re-quire new staging techniques for tu-mors is practical only in a centralizedsolution served on the internet.After e-mail, the most popular appli-cation on the internet is the World WideWeb, which is a hypertext system andas such is useful only when it can eas-ily be navigated through a visualinterface,