Stage 1A. Methodology To Determine A Minimum Technical Standard For Telemedicine

Objectives: To develop a methodology for the experimental study of factors governing the successful interpretation of digital clinical images, leading to the definition of a minimum technical standard for telemedicine applications. To determine the effect of various image resolutions and compression techniques on the objective properties of digital image files.

The Institute for Learning and Research Technology at the University of Bristol, where much of the Stage One work was developed and carried out. Click Here to see a larger version (311kb)

Methodology:

A series of laboratory-based experiments was developed, concentrating on radiographic images (X-rays) and digital images (clinical photographs) at the stages of image acquisition, compression and display, paying particular attention to transmission modes and times.

The issues considered in the development of these methodologies were as follows:

• Selection and acquisition of a “test set” of X-rays and clinical images
• Capture of this “test set” in digital format
• Conversion of the captured digital images to produce a wide range of output files varying in resolution, compression and colour depth
• Techniques for objective assessment of the resulting output files

Additional techniques for subjective assessment of the output files, using expert panel methodology, are described in a companion paper.

The time required to perform these image manipulations, the properties of the resulting output files and the transmission time for a selection of files, using two alternative methods, were also recorded.

Results:

The developed methodology was successfully applied, and was subsequently used to determine a minimum technical standard for minor injuries telemedicine. Image file size declined with reductions in resolution and increases in compression, as expected, but the ratio of maximum to minimum file size did not fall uniformly as the level of compression increased. Over ISDN (integrated systems digital network) a data transfer rate of approximately 10kB per second per channel was obtained

Conclusions:

We have developed a methodological approach to the determination of a minimum technical standard for use in telemedicine. This could be readily applied to a wide range of applications where such data is currently lacking, and would help to prevent clinical research from being undermined by subsequent advances in technology. Technical standards derived from this approach can be readily validated through appropriate clinical trials.