Evaluation of colour images printed by a thermal dye diffusion process.

Dry printing of medical images, without photochemicals, may be based on the principle of thermal dye diffusion. The Drystar (Agfa Gevaert, Mortsel, Belgium) system was evaluated in colour-coded Doppler examinations of the carotid arteries. A total of 25 consecutive patients were examined for the colour test and 37 patients for the black-and-white test. Colour and black-and-white data were available on the same view. The performances of the Drystar were tested against against laser films, matrix films and two types of glossy paper using the following criteria: grey scale, colour scale, quality of reproduction of vascular colouring, registration, endothelial layer, intraluminal echogenicity, spectral resolution, and artefacts. The overall handiness of the document was graded. A significant difference (p = 0.00005) was noted in favour of the Drystar concerning registration, grey scale, spectral resolution and vascular colouring. The global score for handiness of the colour film was 96%. Radiologists preferred the colour hard copy as compared with glossy paper prints. As in the black-and-white test, blue-base and clear-base films obtained with the Drystar were rated inferior to laser films, a double line print mode was included in the printer, giving a density of 2.3 OD.