Polarization of biological tissue reflects birefringent characteristics of tissue components such as collagenous and elastic fibers. Polarimetry imaging techniques have been widely explored for disease diagnosis and therapeutic guidance. However, no traceable standard is available for calibration and validation of the polarimetry devices, partially due to the lack of reliable and stable tissue-simulating phantoms that simulate tissue birefringence properties. We propose a new method to fabricate tissue simulating phantoms that simulate tissue scattering and polarization characteristics. The substrate of the phantoms are made of polydimethylsiloxane (PDMS). The PDMS material is mixed with sucrose to simulate optical rotation characteristics of chiral molecules in tissue. Titanum dioxide (TiO2 ) particles are used to simulate organelle scattering properties of tissue. An electrostatic spinning method produces thin filaments with designated orientation and polarization characteristics to simulate collagen and elastic fiber orientation in biological tissue.By adjusting the concentration of the scattering particles and the arrangements of the fibers, the produced phantoms present different polarization characteristics. The proposed tissue-simulating phantoms can be potentially used to validate and calibrate the polarimetry medical devices.
Proc. SPIE. 9701, Multimodal Biomedical Imaging XI
KEYWORDS: Multimodal imaging, Tissues, Image segmentation, Image processing, Reflectivity, Multispectral imaging, Monte Carlo methods, Image enhancement, Cervical cancer, In vivo imaging, Algorithm development, RGB color model
Cervical cancer is the leading cause of cancer death for women in developing countries. Colposcopy plays an important role in early screening and detection of cervical intraepithelial neoplasia (CIN). In this paper, we developed a multimodal colposcopy system that combines multispectral reflectance, autofluorescence, and RGB imaging for in vivo detection of CIN, which is capable of dynamically recording multimodal data of the same region of interest (ROI). We studied the optical properties of cervical tissue to determine multi-wavelengths for different imaging modalities. Advanced algorithms based on the second derivative spectrum and the fluorescence intensity were developed to differentiate cervical tissue into two categories: squamous normal (SN) and high grade (HG) dysplasia. In the results, the kinetics of cervical reflectance and autofluorescence characteristics pre and post acetic acid application were observed and analyzed, and the image segmentation revealed good consistency with the gold standard of histopathology. Our pilot study demonstrated the clinical potential of this multimodal colposcopic system for in vivo detection of cervical cancer.
Vulvar lichen sclerosis (VLS) is a chronic, inflammatory and mucocutaneous disease of extragenital skin, which often goes undetected for years. The underlying causes are associated with the decrease of VEGF that reduces the blood oxygenation of vulva and the structural changes in the collagen fibrils, which can lead to scarring of the affected area. However, few methods are available for quantitative detection of VLS. Clinician’s examinations are subjective and may lead to misdiagnosis. Spectroscopy is a potentially effective method for noninvasive detection of VLS. In this paper, we developed a polarized, hyperspectral imaging system for quantitative assessment. The system utilized a hyperspectral camera to collect the reflectance images of the entire vulva under Xenon lamp illumination with and without a polarizer in front of the fiber. One image (Ipar) acquired with the AOTF parallel to the polarization of illumination and the other image (Iper) acquired with the AOTF perpendicular to the illumination. This paper compares polarized images of VLS in a pilot clinical study. The collected reflectance data under Xenon lamp illumination without a polarizer are calibrated and the hyperspectral signals are extracted. An IRB approved clinical trial was carried out to evaluate the clinical utility for VLS detection. Our pilot study has demonstrated the technical potential of using this polarized hyperspectral imaging system for in vivo detection of vulvar lichen sclerosis.