# Image Quality Assessment of Digital Image Capturing Devices for Melanoma Detection
## 4 Discussion  
Currently, dermatologists want to identify melanoma at the earliest stage of the disease, when it is, in most cases, similar to a benign pigment mole in the naked eye examination. Dermoscopy improves diagnosis accuracy significantly, even in early stages of melanoma [52; 53; 54; 55; 56; 57]. To detect melanoma at an early stage, the most subtle colour shades (especially brown) and structures need to be identified by dermoscopy, often only in a small part of the lesion [58; 59; 60]. Colour assessment is essential for the clinical diagnosis of skin cancers [6; 25; 26; 27; 28; 29]. Therefore, dermatologists need a dermoscopy device able to provide an image with authentic colours and sharply defined tiny structures in the lesion, as well as an image that offers the same good quality throughout the whole dermoscopic field, including at magnification [6; 8]. Routine handheld dermoscopy is performed increasingly with convenient and affordable systems consisting of handheld dermoscope optics combined with a mobile phone. For people with high levels of pigment moles and, consequently, high risk of melanoma, sovereign diagnosis of melanoma is still possible only with digital dermoscopy and TBP, where the routine use is still limited by the high purchase price and time-consuming diagnostics [61; 62]. Routine handheld dermoscopy is performed increasingly with convenient and affordable systems consisting of handheld dermoscope optics combined with a mobile phone. The handheld dermoscope, when connected to a mobile phone camera or a digital camera, generates a simple, digital dermoscopy system which can provide a good substitute for a highly-priced digital dermoscopy device. Unfortunately, combining camera and different optical systems is not always an optimal solution, since images captured in this fashion may well contain several additional artefacts which could impact the overall image quality negatively [8]. In our study, dermoscopy images were captured using the Dermlite handheld dermoscopy device attached to either a smartphone or a high-resolution camera. The images were then compared with the results obtained on a digital dermoscopy system, which is considered as the gold standard. The results show that the sharpness reduces slightly in the centre of an image if a handheld dermoscope is attached to a smartphone or digital camera. Moreover, the sharpness decreases significantly towards the edges of the image. Another concern is the applied sharpening of the images by a camera signal processor, which has a significant impact on the SFR of a camera system. It increases the contrast on lower spatial frequencies, which makes the image virtually sharper to a human observer [20]. Based on the results of our study, almost all tested cameras use a certain degree of additional sharpening. The overly sharp image emphasises artefacts (pieces of the dead epidermis, hair follicles, dust particles), making it difficult for dermoscopic diagnostics, especially for inexperienced dermatologists. However, furthermore, images are captured frequently by dermatologists in automatic camera mode, although that digital imaging device already allows a manual setting of different camera parameters. In the camera settings, the user can select the most appropriate individual sharpening level. The TBP method is being applied increasingly for skin cancer monitoring, and is used to survey existing and identify new or changing lesions, where high image resolution and sharpness are significant features [11; 24; 38]. State-of-the-art digital dermoscopy systems integrate a high-resolution digital camera for TBP [37]. In this setting, a serial of horizontally oriented photographs is captured until the patient's entire body surface is covered. The weakness of the TBP is that the automated capturing procedure is hugely time-consuming, both for patients and physicians, where the patient has to be photographed in various positions to cover the full body [10].