Ilze Lihacova

Autofluorescence imaging of basal cell carcinoma by smartphone RGB camera

The feasibility of smartphones for in vivo skin autofluorescence imaging has been investigated. Filtered autofluorescence images from the same tissue area were periodically captured by a smartphone RGB camera with subsequent detection of fluorescence intensity decreasing at each image pixel for further imaging the planar distribution of those values. The proposed methodology was tested clinically with 13 basal cell carcinoma and 1 atypical nevus. Several clinical cases and potential future applications of the smartphone-based technique are discussed.

Skin chromphore mapping by means of a modified video-microscope for skin malformation diagnosis

Many spectral imaging devices are commercially available and used to detect certain skin pathology; however an alternative cost-efficient device can provide an advanced spectral analisys of skin. Multispectral device for diagnosis of pigmented skin lesions was developed and tested. Possibilities to map skin chromophores using a modified low-cost digital video-microscope is discussed. It was adapted for an advanced skin microscopy and used for detailed spectral analysis of skin. The device comprises CMOS digital imaging sensor, four-colour LED illumination system and image acquisition optics. The main goal is to obtain a set of spectral images of the skin area of interest for further conversion into maps of the main skin chromophores.

A multispectral imaging approach for diagnostics of skin pathologies

Noninvasive multispectral imaging method was applied for different skin pathology such as nevus, basal cell carcinoma, and melanoma diagnostics. Developed melanoma diagnostic parameter, using three spectral bands (540 nm, 650 nm and 950 nm), was calculated for nevus, melanoma and basal cell carcinoma. Simple multispectral diagnostic device was established and applied for skin assessment. Development and application of multispectral diagnostics method described further in this article.

Evaluation of skin melanoma in spectral range 450-950 nm using principal component analysis

Diagnostic potential of principal component analysis (PCA) of multi-spectral imaging data in the wavelength range 450- 950 nm for distant skin melanoma recognition is discussed. Processing of the measured clinical data by means of PCA resulted in clear separation between malignant melanomas and pigmented nevi.

Quality enhancement of multispectral images for skin cancer optical diagnostics

Melanoma is the least common but deadliest skin cancer, accounting for only about 1% of all cases, but is the cause of the vast majority of skin cancer death. In some parts of the world, especially among western countries, melanoma is becoming more common every year. The detection of melanoma in early stage can be helpful to cure it. Unfortunately, long ques and high prices for dermatology service can result in the skin cancer diagnosis at its later stage, thus increasing the risk of mortality for the patient. It is important to provide a non-invasive optical device for primary care physicians to help diagnose different skin malformation based on obtained optical images. Such device will be able to automatically classify different skin malformations, but the results of classification strongly rely on obtained image quality. This study aims at finding solutions of image quality problems in the area of biophotonics. The resulting image quality depends on hardware capabilities of the object illumination, image sensor, optical system and image post processing (image storage format). Although several of the quality problems of the imaging systems may be prevented in advance, some flaws may not be removed as easily. For example, uneven illumination cases, where skin is not flat (for example: nose, ear). Due to that, it is not possible to create uniform illumination field and the resulting optical image has noticeable differences across it. Sometimes, it is the skin texture that could cause problems for the automatic malformation classification and diagnosis. In this case, image quality enhancement can be helpful for removing different image flaws and raise the precision of malformation classification. In this research methods for solving different image quality problems in multispectral images of skin malformations are proposed. Multispectral image acquisition and proposed methods are tested on noncontact skin cancer analyzing device prototype. Nevertheless, it could be applied on other multispectral image analysis algorithms. Pilot studies of filtering methods show good results when trying to deal with uneven lighting problems in images. Quality enhancement methods include high pass filtering, extraction of nonskin fragments (hair, markers, etc.), image stabilization and other methods. The image quality enhancement techniques were clinically tested on multispectral images of different skin malformations and the results of the study are presented in this paper.

Optical design improvement for noncontact skin cancer diagnostic device

Multispectral diffuse reflectance imaging and autofluorescence photo-bleaching imaging are methods that have been investigated for use in skin disorder diagnostics. In response to the ever-increasing incidence of skin cancer in light skinned populations a new device has been designed incorporating both of these methods. The aim of the study was to create a device that is most efficient in terms of hardware and software parameters for the screening of malignant and benign skin lesions. A set of 525 nm, 630 nm and 980 nm LEDs were used to illuminate the skin area at three wavelengths [1] and a set of 405 nm LEDs were used to induce the skin autofluorescence [2]. For a more homogenous illumination of investigated skin area the optimal placement for LEDs in a cylindrical case was found. The requisite spacing from the camera lens was taken into account to produce a focused RGB image. The geometrical shape of the device allows to capture images of skin that are illuminated solely by the diodes without interference from sunlight or other nearby light sources. Polarizing filters were used to decrease glare effects, therefore preventing image overexposure of very reflective skin areas. 515 nm long pass filter was used to enable the 405 nm excitation while capturing autofluorescence images of the skin. Further improvements to the quality of the diagnostic data can be achieved using reference images to track homogeneity of the intensity and then applying a compensating algorithm on the subsequent screening images. These and other design considerations serve to realize the full potential of the diagnostic method. Results of clinical approbation to assess the efficacy of the new device to diagnose malignant skin lesions will be demonstrated.

A method for skin malformation classification by combining multispectral and skin autofluorescence imaging

As the incidence of skin cancer is still increasing worldwide, there is a high demand for early, non-invasive and inexpensive skin lesion diagnostics. In this article we describe and combine two skin imaging methods: skin autofluorescence (AF) and multispectral criterion p’. To develop this method, we used custom made prototype with 405 nm, 526 nm, 663 nm and 964 nm LED illuminations, perpendicular positioned linear polarizers, 515 nm filter and IDS camera. Our aim is to develop a skin lesion diagnostic device for primary care physicians who do not have experience in dermatology or skin oncology. In this study we included such common benign lesion groups as seborrheic keratosis, hyperkeratosis, melanocytic nevi and hemangiomas, as well two types of skin cancers: basal cell carcinoma and melanoma. By combining skin AF and multispectral p’ imaging methods, we achieved 100% sensitivity and 100% specificity for distinguishing melanoma (3 histologically confirmed cases) from seborrheic keratosis (13 dermatologically confirmed cases), hyperkeratosis (8 histologically and 1 dermatologically confirmed case), melanocytic nevi (23 dermatologically confirmed cases ), basal cell carcinomas (2 histologically and 16 dermatologically confirmed cases) and hemangiomas (8 dermatologically confirmed cases). Unfortunately, currently this method cannot distinguish the basal cell carcinoma group from benign lesion groups.

Semi-automated non-invasive diagnostics method for melanoma differentiation from nevi and pigmented basal cell carcinomas

The incidence of skin cancer is still increasing mostly in in industrialized countries with light- skinned people. Late tumour detection is the main reason of the high mortality associated with skin cancer. The accessibility of early diagnostics of skin cancer in Latvia is limited by several factors, such as high cost of dermatology services, long queues on state funded oncologist examinations, as well as inaccessibility of oncologists in the countryside regions - this is an actual clinical problem. The new strategies and guidelines for skin cancer early detection and post-surgical follow-up intend to realize the full body examination (FBE) by primary care physicians (general practitioners, interns) in combination with classical dermoscopy. To implement this approach, a semi- automated method was established. Developed software analyses the combination of 3 optical density images at 540 nm, 650 nm, and 950 nm from pigmented skin malformations and classifies them into three groups- nevi, pigmented basal cell carcinoma or melanoma.

Monitoring soft tissue coagulation by optical spectroscopy

Laser tissue welding (LTW) or laser tissue soldering (LTS) is investigated since many years for treatment of incisions, wound closure and anastomosis of vessels [1, 2]. Depending on the process, a certain temperature in the range between 65 °C to 85 °C must be reached and held for a few seconds. Care has to be taken not to overheat the tissue, otherwise necrosis or tissue carbonization may occur and will impair wound healing. Usually the temperature is monitored during the process to control the laser power [3]. This requires either bulky equipment or expensive and fragile infrared fibers to feed the temperature signal to an infrared detector. Alternatively, changes in tissue morphology can be directly observed by analysis of spectral reflectance. We investigate spectral changes in the range between 400 nm to 900 nm wavelength. Characteristic spectral changes occur when the temperature of tissue samples increase above 70 °C which is a typical setpoint value for temperature control of coagulation. We conclude that simple spectroscopy in the visible range can provide valuable information during LTS and LTW and probably replace the delicate measurement of temperature. A major advantage is that optical measurements can be performed using standard optical fibers and can be easily integrated into a surgical tool.

Evaluation of skin pathologies by RGB autofluorescence imaging

A clinical trial on autofluorescence imaging of malignant and non-malignant skin pathologies comprising 32 basal cell carcinomas (BCC), 4 malignant melanomas (MM), 1 squamous cell carcinoma (SCC), 89 nevi, 14 dysplastic nevi, 20 hemangiomas, 23 seborrheic keratoses, 4 hyperkeratoses, 3 actinic keratoses, 3 psoriasis, 1 dematitis, 2 dermatofibromas, 5 papillofibromas, 12 lupus erythematosus, 7 purpura, 6 bruises, 5 freckles, 3 fungal infections, 1 burn, 1 tattoo, 1 age spot, 1 vitiligo, 32 postoperative scars, 8 post cream therapy BCCs, 4 post radiation therapy scars, 2 post laser therapy scars, 1 post freezing scar as well as 114 reference images of healthy skin was performed. The sequence of autofluorescence images of skin pathologies were recorded by smartphone RGB camera under continuous 405 nm LED excitation during 20 seconds with 0.5 fps. Obtained image sequences further were processed with subsequent extraction of autofluorescence intensity and photobleaching parameters.