Digital volumetric measurement of cutaneous leishmaniasis lesions: Blur estimation method

Cutaneous leishmaniasis is a common parasitic infestation in Iran. With recent advantages in digital imaging, we have devised a novel non-contact objective method of measuring lesions.

The aim of the study was to design a software system that analyzes images of cutaneous leishmaniasis lesions, objectively assess and monitor volume.

A photographic technique along with an image processing algorithm was applied to extract a three-dimensional map of the lesion from a simple two-dimensional picture. This method recovers depth on the basis of blur estimation. A macro lens with a low depth of field was used to blur the objects out of focus. To assess and compare the results, a polymer mold of the corresponding lesion was made and filled with liquid. The volume of liquid corresponded to the volume of the lesion. A total of thirty-seven patients were enrolled, and 48 lesions were analyzed.

The mean volume measured by image processing was 159 μl (range: 8-685 μl), in comparison to an average of 170 μl (range: 6-800 μl) obtained from the molds. This was not significantly different. Statistical analysis by the Pearson correlation test showed a 'very good fit' correlation between these measured volumes (P < 0.001, r = 0.938).

The location and height of lesions were two important limitations in implementing this technique. If the lesion location is in the curvature region of body or the lesion height is less than 1 mm or more than 1 cm, this method will lose precision and accuracy.

Image processing with blur estimation technique is an accurate and precise method to measure the volume of lesions in cutaneous leishmaniasis.