Technical Aspects of Image and Process

Video vs store and forward

This document has been drawn up with store and forward in mind as the main means of teledermatology. Earlier efforts at using real time video consultation had some significant clinical and educational benefits, but were inconvenient and time consuming for the clinicians. There remains the possibility that small video clips can be compressed and sent for store and forward consultation, but there are few services still offering real time video consultation.

Specification of hardware and software

PC: modern processor speeds, hard disc size and 256MB of RAM is adequate for most routine image handling and short term storage.

Larger (17-21inch) monitors with better quality screens yield the best images and allow for multiple images and text to be reviewed simultaneously

Access to network for back up is valuable.

Alternatively, a cd or dvd writer within the PC.

Access to the internet is likely to be through ISDN, ISDN2 or Broadband and these facilities are needed to download images without undue delay. Telephone lines would not be on the NHSnet and a separate encryption process would be needed for patient identifiable material. Normal telephone lines would be unacceptably slow for large image files

Compatibility with GP systems eg EMIS

In primary care, the GP/nurse will usually be using their e-mail application combined with the photo-editing application as the main software. They may attach documents created in Word or elements of the patient history from the GP electronic patient record, such as EMIS. The photo editing software is the only element that will be different from their usual software and rarely causes any problems. Most modern GP patient record systems allow electronic linkage of images and e-mails.

Photo quality, specification, number and format

Images available through current medium specification digital cameras are usually adequate. Current 2-4Mpixel images are fine. Details of individual lesions can be excellent if a camera with a good macro option is used.

Technical aspects of taking pictures are important and these should be worked on in order that clinical referrals are not wasted through poor photography. In particular:

• Experiment with lighting
• Determine optimum circumstances and use of flash
• Experiment with different backgrounds
• Determine benefit of global shots supplemented by detail shots from different angles
• Three photographs usually adequate

Images would normally be

• JPEGs (Joint Photographic Expert Group): this defines the type of compression that the image is subjected to in order that the file is kept to an optimum size whilst allowing retention of maximal detail.
• 1600x1200 pixel resolution