Mueller polarimetric imaging appeared to be very promising to detect the modifications in the microstructure of the uterine cervix due to the development of a precancerous lesion, thus providing very useful information for diagnostics to which practitioner cannot to access with classic color imaging. The first multispectral Mueller Polarimetric Colposcope (MPC) for the in vivo analysis of the uterine cervix will be presented. It has been obtained by miniaturizing a Mueller polarimetric imaging system and “grafting” it on a conventional colposcope, which is a low magnification binocular system, currently used in medical practice to examine the uterine cervix for detection of precancerous lesions. The multispectral MPC enables to obtain reliable Mueller polarimetric images in less than 2 seconds with a spatial resolution of 100 μm simultaneously at 450, 550 and 650 nm. Currently, it is being tested in vivo in the University Hospital of Kremlin Bicêtre in France. In order to evaluate the performance of the technique, polarimetric images need to be compared with histological analyses of biopsies. The procedure developed in collaboration with medical doctors to obtain an accurate correlation between polarimetric images and biopsies will be described.
Mueller polarimetry has been shown to effectively detect multiple pathologies on a striking variety of biological tissues. The ongoing challenge is to implement Mueller polarimetry into the clinical practice in-vivo. This technique is suitable for this purpose since it provides wide field images (up to 20 cm2) well adapted to the exploration of entire organs while revealing information on their microstructure. In addition, it is non-invasive, label-free and non-destructive. One instrument of great interest for biomedical diagnostics in vivo is the conventional rigid endoscope, also called laparoscope. This instrument is used to explore the inner cavities of the human body and is a standard in many minimally invasive surgery applications. However, it is implemented by using conventional white light intensity imaging which does not provide enough contrast to identify, for example, tumor margins during surgical resection. Mueller polarimetric imaging could provide useful contrast which can considerably improve the definition of these margins. However, to adapt a conventional laparoscope to Mueller polarimetric imaging is an instrumental challenge due to its complex polarimetric response. In this work, we provide a detailed characterization of the polarimetric properties of a conventional laparoscope. It is shown that a conventional laparoscope is characterized at the same time by birefringence and strong spectral depolarization that can be reduced by reducing the spectral bandwidth. The origin of these polarimetric effects have been investigated and modeled. Our work provides useful knowledge about implementing rigid endoscopes in polarimetric applications.
Mueller Polarimetric Imaging (MPI) showed promising results in biomedical applications, especially for early detection of precancerous lesions on biological tissues. This technique is label-free, non-invasive and can be implemented with a large field of view (up to several cm2) to image wide areas of biological tissues while providing information on its microstructure. The development of innovative (MPI) systems, able to analyze biological tissues in vivo on human patients, remains an instrumental challenge. Our goal is to build miniaturized and compact full-field MPI systems based on Ferroelectric Liquid Crystals (FLCs) capable of performing a multispectral accurate analysis of biological tissues in vivo. In this work, an innovative approach is showed to realize optimized and fast FLCs-based MPI systems able to perform full-field imaging acquisitions in the spectral range between 450 and 700nm with error less than 1% on all the elements of measured Mueller matrices. This system can be accurately calibrated by using the Eigenvalue Calibration Method (ECM) also in presence of high residual instrumental depolarization. This approach enables us to realize compact and reliable MPI systems which can be easily integrated into existing instruments currently used in medical practice.
Recent developments have shown that conical diffraction by a biaxial crystal can create a vortex beam for use in 2D STED microscopy. It has been shown that this concept can be extended and also generate the depletion distributions used for 3D STED microscopy. A single beam passes through a biaxial crystal that creates two co-propagating, co-localized beams; the first one is used for lateral depletion, and the other one for axial depletion. The two beams are crossed-polarized and thus do not interfere. We will show that the 3D distribution can be made achromatic, i.e. several depletion wavelengths can travel through a common path and still be shaped into the appropriate pattern by optimizing the geometry of the system. This system enables true one-channel 3D depletion at multiple wavelengths ranging from 580nm to 770nm, thus covering most of the conventional depletion wavelengths currently used. Preliminary results of depletion PSFs will be presented and the advantages and limitations of this system will be discussed as well as the experimental considerations required to successfully obtain the desired PSFs.