Three-dimensional representation of triple spectral line imaging data as an option for noncontact skin diagnostics

Abstract

. Significance: Skin malformations in dermatology are mostly evaluated subjectively, based on a doctor’s experience and visual perception; an option for objective quantitative skin assessment is camera-based spectrally selective diagnostics. Multispectral imaging is a technique capable to provide information about concentrations of the absorbing chromophores and their distribution over the malformation in a noncontact way. Conversion of spectral images into distribution maps of chromophores can be performed by means of the modified Beer–Lambert law. However, such distribution maps represent only single specific cases, therefore, some extensive method for data comparison is needed. Aim: This study aims to develop a more informative approach for identification and characterization of skin malformations using three-dimensional (3D) representation of triple spectral line imaging data. Approach: The 3D-representation method is experimentally tested on eight different skin pathology types, including both benign and malignant pathologies; an imaging device ensuring uniform three laser line (448, 532, and 659 nm) illumination is used. Three spectral line images are extracted from a single snapshot RGB image data, with subsequent calculation of attenuation coefficients for each working wavelength at every image pixel and represented as 3D graphs. Skin chromophore content variations in malformations are represented in a similar way. Results: Clinical measurement results for 99 skin pathologies, including basal cell carcinomas, melanoma, dermal nevi, combined nevi, junctional nevi, blue nevi, seborrheic keratosis, and hemangiomas. They are presented as 3D spectral attenuation maps exhibiting specific individual features for each group of pathologies. Along with intensity attenuation maps, 3D maps for content variations of three main skin chromophores (melanin, oxyhemoglobin, and deoxyhemoglobin), calculated in frame of a model based on modified Beer–Lambert law, are also presented. Advantages and disadvantages of the proposed data representation method are discussed. Conclusions: The described 3D-representation method of triple spectral line imaging data shows promising potential for objective quantitative noncontact diagnosis of skin pathologies.

3D-representation of skin malformations using spectral line imaging and modified Beer-Lambert law

“…These coefficients are used for chromophore map calculations. Afterwards, chromophore values in each malformation are converted to 3D clouds in attenuation coefficient graphs 20 .…”

“…Although some parts of the different skin malformation clouds overlap, each malformation type occupies its own volume fraction in the three-dimensional graphs of attenuation coefficients. For a more detailed description of the 3Drepresentation method of triple spectral line imaging data see the publication 20 .…”

Diagnostic spectral imaging of skin and nasal mucosa by RGB laser-based prototype devices

“…Spectral imaging under triple laser line illumination has been successfully applied for remote distribution mapping of three main skin chromophores (melanin, oxy-hemoglobin and deoxy-hemoglobin) in cutaneous malformations [10,11]. A similar approach was implemented by using an integrated "3 in 1" RGB laser module emitting simultaneously three spectral lines in the blue, green and red regions of visible spectrum [12], while uniform illumination of the examined skin region was ensured by means of laser coupled side emitting optical fiber loops [13][14][15].…”