The effect of resolution, compression, colour depth and display modality on the accuracy of accident and emergency telemedicine.

There are no current recommendations regarding the minimum technical specification for realtime telemedicine consultation in accident and emergency (A and E) practice. We assessed the effect of image resolution, compression, colour depth and display modality on perceived image quality and telediagnosis. Test sets of digitized radiographs and clinical images were subjected to a series of standardized manipulations and the resulting output files were evaluated by an expert panel using image scoring and receiver operating characteristic (ROC) analysis. For telemedicine in A and E work, the minimum technical specification should be regarded as images containing at least 250,000 pixels, compressed at up to JPEG 50 (or GIF for colour images) and displayed on a high-resolution computer monitor. These specifications resulted in average file sizes of 17 kByte for digital images and 9 kByte for radiographs.