Method of spatial scanning of modulated laser radiation for outline imaging of interphalangeal joints
Svetlana Shmavonyan1, Aleksandr Khanbekyan1, Marina Movsisyan1,
Valery Tuchin2,3, and Aram Papoyan1; 1Institute for Physical Research of National Academy of Sciences of Armenia, Ashtarak-2, Armenia; 2Saratov State University, Institute of Physics and Science Medical Center, Saratov, Russian Federation; 3Institute of Precision Mechanics and Control, FRC “Saratov Scientific Centre of the RAS,” Saratov, Russian Federation
Abstract
Optical transmission imaging is an inexpensive and noninvasive method of examining biological tissues and structures, but due to strong scattering, its applicability is limited to millimeter-thick samples, thus preventing in vivo studies of centimeter-thick biological organs. The development of a technique that overcomes the limitation imposed by scattering will significantly expand the scope of the application of transillumination
imaging, allowing the examination or diagnosis of biological objects of centimeter thickness, in particular, interphalangeal joints. The approach used is based on a previously developed method of highly sensitive registration of predominantly ballistic and snake photons when scanning modulated laser radiation. In addition, to obtain a contour image, a technique of selective registration across the profile of a Gaussian laser beam was used, which made it possible to obtain high spatial resolution with a large diameter of a collimated laser beam. An optical clearing agent was used to mitigate the scattering
imposed by the skin. The method was tested on a model object and applied to obtain the
contour of the interphalangeal joint. The resulting joint contour matches the actual
shape, but its width in the image is larger than the actual width. Calculations show
that the size of the structure in the image also depends on the intensity and diameter
of the laser beam, as well as the extinction coefficient of the sample. It is shown that,
given the other parameters, the extinction coefficient can be determined from the
joint image space. The effect of the clearing agent on the clarity and contrast of the
image is quantitatively analyzed, and a reduction in the scattering coefficient (by 9%
to 14%) is estimated. The suggested method has been shown to be efficient for deep-tissueimaging of biological objects up to several centimeters thick, particularly joints,
revealing the outline of structural features. We have shown that the use of an optical
clearing agent allows reproducible images to be obtained with noticeably higher
contrast and clarity, sufficient for preliminary express diagnostics of pathologies.
Speaker
Marina Movsisyan
Institute for Physical Research
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