Evaluation of diffuse technologies: the case of digital imaging networks.

There have been significant developments in recent years in the methodologies and methods for the evaluation of a wide range of health technologies. There remain, though, many technologies which are difficult to evaluate. Often the difficulty stems from the complexity of the technologies themselves, which are in effect hybrids, comprising combinations of several distinct elements. In this paper these are termed 'diffuse' technologies, because the different elements exert different costs and effects, often across several different services. Computer networks are one, increasingly important, example of such technologies in health care. While it is possible to evaluate individual elements of such technologies, it is not clear how to evaluate the technology as a whole, where the whole may be greater (or less) than the sum of the parts. The paper outlines a seven-stage framework for the evaluation of diffuse technologies. The general principles of evaluation are illustrated using the example of picture archiving and communication systems (PACS), which are computer systems designed to capture, store and distribute electronic radiological images within a hospital.