Polarized Multispectral Imaging for Tissue Lesion Characterization.
详细信息
文摘
Scars are an atypical reaction of the body to trauma,surgery and burn wounds. Scarring can lead to significant cosmetic,psychosocial,and functional consequences in patients. Therefore,quantitative assessment and precise treatment plans are needed in clinical scar diagnosis and management. The Vancouver Scar Scale,VSS,is one of the most commonly used clinical scar assessment tools and relies only on the physicians subjective evaluation of skin pliability,height,vascularity,and pigmentation. To date,no entirely objective method has been available for scar assessment,so there is a continued need for better techniques to monitor patients with scars. We have introduced a novel polarized multispectral imaging system combining out-of-plane Stokes polarimetry and Spatial Frequency Domain Imaging,SFDI. The main idea behind this system was estimating oxy- and deoxy-hemoglobin,water and melanin contents and cellularity of scars using the SFDI technique,and degrees of roughness and directional anisotropy with Stokes polarimetry. We introduced the earlier version of the polarized multispectral imaging system,an out-of-plane Stokes polarimetry,as a way of conducting a roughness assessment. Valuable information in early stages of skin cancer was obtained from the analysis of epidermis roughness. Optimal treatment of skin cancer before it metastasizes critically depends on early diagnosis and treatment. The scattering of polarized light by rough skin samples showed behavior,which was partially predicted by a facet scattering model. Clinical tests were conducted on patients with different pigmented lesions. Images were captured,analyzed,and the polarization properties were presented in terms of the principal angle of the polarization ellipse and the degree of polarization. We showed that there was a separation between different groups of patients. Ultimately,the same concept of imaging was applied for scar roughness assessment. Overproduction and preferential alignment of skin collagen is a typical occurrence in scar formation. Assessing collagen alignment is of interest when evaluating a therapeutic strategy and its outcome. We introduced a novel theoretical and experimental methodology for the quantification of collagen alignment based on polarized light transport. A novel polarized Monte Carlo model was devised to predict and measure the impact of birefringence on an impinging linearly polarized light beam. Ex-vivo experiments by an out-of-plane Stokes imaging system conducted on a group of bovine leg tendons,a biological sample consisting of highly packed type I collagen fibers,partially agreed with the analytical results. Among scar therapeutic methods,compression therapy has long been a standard treatment for hypertrophic scar prevention. We have designed and built an Automatic Pressure Delivery System,APDS,to apply and maintain constant pressure on tissue as close as possible to the set point. Due to the lack of quantifiable metrics on scar formation,scant evidence exists of compression therapys efficacy. The main goal of this research was to fill this gap in scar knowledge using our imaging system and the pressure delivery device. Dermal wounds were created in a swine model and allowed to form into scars. Hypertrophic scars were monitored and assessed in-vivo using the developed polarized multispectral imaging system to investigate the influence of compression therapy performed with the constructed APDS. Pressure treated and untreated scars were assessed at various points in time using the imaging system. Results showed promising correlations with clinical and histological evaluations.