Clinical study on the comparison of dermoscopic images using two wavelengths of near‐ultraviolet‐visible light

Abstract

Abstract Background Light absorption by melanin is greater in the ultraviolet spectrum than in the visible light spectrum. Purple light in the near‐ultraviolet–visible region (380–430 nm) also corresponds to a highly absorptive wavelength of melanin. Therefore, images captured under purple light are remarkably suited to detect subtle alterations in skin pigment contents. Objectives We compared two prototype dermoscopy cameras (DZ‐D100; Casio Computer Co., Ltd.): one with a 385 nm light (P385) and the other with a 405 nm light (P405), to clarify which wavelength could more clearly show dermoscopic structures. Methods Sixteen Japanese patients with 19 lesions, who visited our department were photographed with the P385 and P405 cameras under the same conditions. We evaluated the visual perception of lines, dots/clods, lesion borders and background around the lesion, as well as exposure, including appropriate brightness and underexposure, using the scores. Results Underexposure was significantly less in the P385 image than in the P405 image (p < 0.0001), while lines (p < 0.01) and lesion borders (p < 0.05) were significantly more distinct. Furthermore, visual perception of lines (p < 0.01) and lesion borders (p < 0.05) were significantly better in the P385 images. However, other visual perception items showed no significant differences between the two images. One exception was with the dermoscopy of melanocytic naevus in a patient with albinism, where the lines and dots/clods were clear in the P405 image but blurred in the P385 image. Conclusions When used as a complement to conventional dermoscopy images, the P385 images are thought to be less underexposed and easier to use in diagnosing lesions in slightly pigmented skin types, including in the Japanese who were the participants of this study. Meanwhile, the P405 images are potentially useful in the evaluation of light skin‐type lesions.

Keywords

• blocked‐up shadows
• dermoscopy camera
• near‐ultraviolet‐visible light
• skin lesion diagnosis
• ultraviolet photography