Digital imaging: an accurate and easy method of measuring foot ulcers

A progressive reduction in the area of foot ulcer on serial measurement is traditionally done by tracing the margin of the ulcer on a transparent film and counting the number of squares on a graph paper underneath. We set out to use and validate the measurement of foot ulcers using a digital imaging technique and compare this with the traditional method.

Thirty diabetic foot ulcers (18 patients) were studied over 10 weeks. Each ulcer was traced by three independent observers with a pen over a flexigrid Opsite film and digital photographs were taken. Each observer calculated the area of an ulcer first using a 1-mm2 graph paper and then with the computer software. For each ulcer we calculated the mean area using measurements from all the observers. We then calculated the deviation from this mean for each observer.

There was significantly less interobserver variation using the digital image than the traditional method with mean coefficient of variation (CV) 16% vs. 27%; P = 0.05.

The digital imaging method was faster and easier to use and the patients preferred it, as it was a noncontact method. In addition it also provides a photographic record for comparison.